Anon (2006). West nile virus activity--United States, January 1-November 7, 2006. MMWR. Morbidity and Mortality Weekly Report 55(44): 1204-1205.
Abstract: This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Standard Time, November 7, 2006. A total of 41 states and the District of Columbia had reported 3,830 cases of human WNV illness to CDC.
Descriptors: West Nile fever, bird diseases, culicidae, horse diseases, rodent diseases, sciuridae, United States, West Nile virus isolation and purification.
Anon (2006). West Nile virus activity--United States, January 1-October 10, 2006. MMWR. Morbidity and Mortality Weekly Report 55(40): 1097-1098.
Abstract: This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, October 10, 2006. A total of 41 states and the District of Columbia had reported 3,135 cases of human WNV illness to CDC. A total of 1,717 (55%) cases for which such data were available occurred in males; median age of patients was 50 years (range: 3 months-99 years). Dates of illness onset ranged from January 6 to September 25; a total of 97 cases were fatal.
Descriptors: West Nile fever epidemiology, West Nile virus isolation and purification, bird diseases, culicidae, horse diseases, rodent diseases, sciuridae, United States.
Anon (2006). West Nile virus activity--United States, January 1-September 12, 2006. MMWR. Morbidity and Mortality Weekly Report 55(36): 996.
Abstract: This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, September 12, 2006. A total of 36 states and the District of Columbia had reported 1,634 cases of human WNV illness to CDC. A total of 921 (57%) cases for which such data were available occurred in males; median age of patients was 51 years (range: 3 months-95 years). Dates of illness onset ranged from January 6 to September 10; a total of 52 cases were fatal.
Descriptors: West Nile fever, humans, birds, humans, United States, fatality reports.
Anon (2006). West Nile virus activity--United States, January 1-August 15, 2006. Morbidity and Mortality Weekly Report 55(32): 879-880.
Abstract: This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, August 15, 2006. A total of 26 states had reported 388 cases of human WNV illness to CDC. A total of 214 (56%) cases for which such data were available occurred in males; median age of patients was 49 years (range: 2-91 years). Dates of illness onset ranged from January 6 to August 10; a total of 13 cases were fatal. A total of 68 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2006. Of these, 20 were reported from Nebraska; 18 were reported from Texas; five were reported from California; four were reported from Utah; three each were reported from Oklahoma and South Dakota; two each were reported from Idaho, Iowa, Kentucky, and Mississippi; and one each was reported from Arizona, Colorado, Minnesota, Nevada, North Dakota, Wisconsin, and Wyoming. Of the 68 PVDs, 10 persons (median age: 43 years [range: 18-59 years]) subsequently had West Nile fever.
Descriptors: West Nile fever epidemiology, humans, bird diseases, culicidae, horse diseases, rodent diseases, United StatesWest Nile virus isolation and purification.
Anon (2006). Assessing capacity for surveillance, prevention, and control of West Nile virus infection--United States, 1999 and 2004. Morbidity and Mortality Weekly Report 55(6): 150-153.
Abstract: Indigenous human disease caused by West Nile virus (WNV) was first identified in the United States in August 1999 in the greater New York City area. By the end of 2004, human WNV disease had been reported in all states except Washington, Hawaii, and Alaska, and WNV transmission to humans had been documented by five routes: mosquito bites (principally from Culex spp.), blood transfusions, organ transplantation, transplacental transfer, and breastfeeding. During 1999-2005, a total of 19,525 cases of WNV disease in humans and 771 deaths were reported in the United States. In 2000, CDC first published guidelines for WNV surveillance, prevention, and control and created ArboNET, an electronic surveillance and reporting system. Beginning in 1999, WNV surveillance and prevention activities had been initiated in selected states and large cities through the CDC Epidemiology and Laboratory Capacity (ELC) cooperative agreements for emerging infectious diseases and subsequently expanded to all 50 states, six large cities/counties, and Puerto Rico. In 2005, to assess the capacity of state and large-city/county health departments to conduct WNV surveillance, prevention, and control activities, the Council of State and Territorial Epidemiologists (CSTE), with assistance from the Association of Public Health Laboratories (APHL) and CDC, surveyed WNV programs in the 50 states and six large-city/county health departments. This report describes the results of that assessment, which indicated that all participating states and cities had well-developed surveillance and control programs for human, avian, equine, or mosquito WNV.
Descriptors: public health practice, West Nile fever epidemiology, prevention and control, population surveillance, United States, West Nile virus.
Anon (2005). West Nile virus activity--United States, January 1-December 1, 2005. Morbidity and Mortality Weekly Report 54(49): 1253-1256.
Abstract: West Nile virus (WNV) is the leading cause of arboviral encephalitis in the United States. Originally discovered in Africa in 1937, WNV was first detected in the western hemisphere in 1999 in New York City. Since then it has caused seasonal epidemics of febrile illness and severe neurologic disease. During January 1-December 1, 2005, a total of 2,744 cases of WNV disease in humans were reported in the United States, an increase from 2,359 during the same period in 2004. A total of 1,165 cases were WNV neuroinvasive disease (WNND). WNV infections in humans, birds, mosquitoes, and nonhuman mammals are reported to CDC through ArboNET, an Internet-based arbovirus surveillance system managed by state health departments and CDC. During 2005, WNV transmission to humans or animals expanded into 21 counties that had not previously reported transmission and recurred in 1,196 counties where transmission had been reported in previous years. This report summarizes provisional WNV surveillance data through December 1, 2005, and highlights the need for ongoing surveillance, mosquito control, promotion of personal protection from mosquito bites, and research into additional prevention strategies.
Descriptors: West Nile fever epidemiology, birds, culicidae, dogs, horses, population surveillance, sciuridae, United States, West Nile virus isolation and purification.
Anon (2005). Update: West Nile virus activity--United States, 2005. Morbidity and Mortality Weekly Report 54(43): 1105-1106.
Abstract: This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Standard Time, November 1, 2005.
Descriptors: West Nile fever epidemiology, birds, culicidae, dogs, horses, sciuridae, United States, West Nile virus isolation and purification.
Bell, J.A., C.M. Brewer, N.J. Mickelson, G.W. Garman, and J.A. Vaughan (2006). West Nile virus epizootiology, central Red River Valley, North Dakota and Minnesota, 2002-2005. Emerging Infectious Diseases 12(8): 1245-1247.
Abstract: West Nile virus (WNV) epizootiology was monitored from 2002 through 2005 in the area surrounding Grand Forks, North Dakota. Mosquitoes were tested for infection, and birds were surveyed for antibodies. In 2003, WNV was epidemic; in 2004, cool temperatures precluded WNV amplification; and in 2005, immunity in passerines decreased, but did not preclude, WNV amplification.
Descriptors: bird diseases, West Nile virus, insect vectors, Minnesota, North Dakota, zoonoses.
Beveroth, T.A., M.P. Ward, R.L. Lampman, A.M. Ringia, and R.J. Novak (2006). Changes in seroprevalence of West Nile virus across Illinois in free-ranging birds from 2001 through 2004. American Journal of Tropical Medicine and Hygiene 74(1): 174-179. ISSN: 0002-9637.
Abstract: Of the 5,236 birds sampled for antibodies to West Nile virus (WNV) in Illinois from 2001 through 2004, 348 (6.6%) birds were seropositive. Our multiple year surveillance identified several avian species that had particularly high percentages of seropositive individuals. The importance of these species in the enzootic and/or epizootic transmission of WNV is discussed relative to their regional abundance and literature on host competency. The species with the highest exposure rates to WNV differed both temporally and regionally. In general, birds that bred or were born in Illinois were more likely to have antibodies than transient birds. There was also a significant difference in the seroprevalence between adults (12.1%) and juveniles (5.5%), indicating that the acquired antibody response from previous years is a critical concern when interpreting seroprevalence rates in wild-caught birds. The most common hosts for St. Louis encephalitis virus were also the most common hosts for WNV, which strongly supports the role of similar vectors for both flaviviruses. Avian species with high WNV seroprevalence rates tended to be those that bred throughout the year, have open cup nests, and live in close proximity to humans.
Descriptors: aves, age, viral disease prevalence relations, viral diseases, West Nile virus, host records, prevalence, annual changes and age relations, Illinois, viral disease prevalence and host records.
Bradford, C.M., M.A. Nascarella, T.H. Burns, J.R. Montford, E.J. Marsland, C.B. Pepper, and S.M. Presley (2005). First report of West Nile virus in mosquitoes from Lubbock County, Texas. Journal of the American Mosquito Control Association 21(1): 102-105.
Abstract: Since July 2002, ongoing surveillance efforts have been conducted to determine potential vectors of West Nile virus (WNV) and Saint Louis encephalitis virus (SLEV) in the mosquito population occurring in Lubbock County, Texas. Adult mosquitoes collected in Lubbock County during 2002 and 2003 represented 7 genera, with Culex tarsalis and Ochlerotatus sollicitans being the predominant species collected. Mosquitoes were initially screened for WNV and SLEV by using the VecTest antigen panel assay. Positive VecTest results were confirmed by reverse transcriptase-polymerase chain reaction. West Nile virus-positive pools of mosquitoes were detected in 2002 and 2003, with the majority of the positive pools consisting of Cx. tarsalis. None of the mosquito pools tested positive for SLEV.
Descriptors: culicidae, West Nile virus, St. Louis encephalitis virus, ochlerotatus, reverse transcriptase polymerase chain reaction, Texas.
Bunde, J.M., E.J. Heske, N.E. Mateus Pinilla, J.E. Hofmann, and R.J. Novak (2006). A survey for West Nile virus in bats from Illinois. Journal of Wildlife Diseases 42(2): 455-458.
Abstract: A blocking enzyme-linked immunosorbent assay was used to test 97 serum samples from big brown bats (Eptesicus fuscus) captured in six counties in Illinois between May 2002 and February 2004 for West Nile virus (WNV) antibodies. One female big brown bat tested positive for WNV antibodies. Samples of kidney, liver, and heart tissue were collected from 312 bats of seven species that were submitted to the Illinois (USA) Department of Public Health or the Illinois Department of Agriculture diagnostic laboratories between January 2001 and December 2003. Tissue samples were tested for WNV using TaqMan reverse transcriptase polymerase chain reaction and all were negative. Prevalence of WNV antibodies in the bats (1%) was lower than previously reported for other flaviviruses, but similar to the prevalence (2%) of WNV antibodies reported in bats from New Jersey and New York, USA. Additional research is needed to determine potential impact of WNV infections on bats and to determine whether they play a role in the WNV transmission cycle.
Descriptors: viral blood antibodies, big brown bats, West Nile fever, West Nile virus, enzyme linked immunosorbent assay methods, myocardium, reverse transcriptase polymerase chain reaction methods.
Busch, M.P., D.J. Wright, B. Custer, L.H. Tobler, S.L. Stramer, S.H. Kleinman, H.E. Prince, C. Bianco, G. Foster, L.R. Petersen, G. Nemo, and S.A. Glynn (2006). West Nile virus infections projected from blood donor screening data, United States, 2003. Emerging Infectious Diseases 12(3): 395-402.
Abstract: National blood donor screening for West Nile virus (WNV) RNA using minipool nucleic acid amplification testing (MP-NAT) was implemented in the United States in July 2003. We compiled national NAT yield data and performed WNV immunoglobulin M (IgM) testing in 1 WNV-epidemic region (North Dakota). State-specific MP-NAT yield, antibody seroprevalence, and the average time RNA is detectable by MP-NAT were used to estimate incident infections in 2003. WNV donor screening yielded 944 confirmed viremic donors. MP-NAT yield peaked in August with >0.5% of donations positive for WNV RNA in 4 states. Peak IgM seroprevalence for North Dakota was 5.2% in late September. The average time viremia is detectable by MP-NAT was 6.9 days (95% confidence interval [CI] 3.0-10.7). An estimated 735,000 (95% CI 322,000-1,147,000) infections occurred in 2003, with 256 (95% CI 112-401) infections per neuroinvasive case. In addition to preventing transfusion-transmitted WNV infection, donor screening can serve as a tool to monitor seasonal incidence in the general population.
Descriptors: blood donors, West Nile fever, RNA, viral blood, seasons, sensitivity and specificity, time factors, United State, West Nile virus.
Chadalavada, S. (2005). A procedure to identify West Nile virus potential risk areas for seven counties in Nebraska using GIS and remote sensing. Dissertation, University of Nebraska. Lincoln:
Descriptors: West Nile Virus, potential risk areas, identify, procedure, GIS, remote sensing, Nebraska.
Notes: Thesis (M.A.).
Chevalier, V., R. Lancelot, A. Diaite, B. Mondet, B. Sall, and X. DE Lamballerie (2006). Serological assessment of west nile Fever virus activity in the pastoral system of ferlo, senegal. Annals of the New York Academy of Sciences 1081: 216-25.
Abstract: The Ferlo area (north-central Senegal) is characterized by a system of temporary ponds favorable to arboviruses among which West Nile fever (WNF) was already identified. During the rainy season in 2003, a serological study was undertaken on horses to assess the activity of the WNF virus (WNFV) in Barkedji (Ferlo). The observed serological prevalence rate was 78.3% for neutralizing antibodies, with a 95% confidence interval (CI) of [64.0, 92.7]. This prevalence rate significantly increased with age (P = 10(-5)). This study confirmed that WNF was endemic in the Ferlo. The transmission risks depended on the introduction of the WNFV in the ecosystem-probably with migrating birds, on its amplification in hosts and on the vector-population dynamic. Further studies are needed to investigate how the cycle is initiated in Barkedji at the beginning of the rainy season and the impact of climatic variations on the risk of transmission of WNF. A surveillance system should be implemented: (a) to assess the clinical impact of the WNF on human and equine populations, (b) to provide an early detection of virulent strains, and (c) to assess the risk of WNF transmission to disease-free ecosystems via migrating birds.
Descriptors: West Nile virus, serological assessment, virus activity, ponds, horses, antibodies, transmission, migrating birds.
Cooke, W.H.3., K. Grala, and R.C. Wallis (2006). Avian GIS models signal human risk for West Nile virus in Mississippi. International Journal of Health Geographics 5: 36.
Abstract: BACKGROUND: West Nile virus (WNV) poses a significant health risk for residents of Mississippi. Physicians and state health officials are interested in new and efficient methods for monitoring disease spread and predicting future outbreaks. Geographic Information Systems (GIS) models have the potential to support these efforts. Environmental conditions favorable for mosquito habitat were modeled using GIS to derive WNV risk maps for Mississippi. Variables important to WNV dissemination were selected and classified as static and dynamic. The static variables included road density, stream density, slope, and vegetation. The dynamic variable represented seasonal water budget and was calculated using precipitation and evaporation estimates. Significance tests provided deterministic evidence of variable importance to the models. RESULTS: Several models were developed to estimate WNV risk including a landscape-base model and seasonal climatic sub-models. P-values from t-tests guided variable importance ranking. Variables were ranked and weights assigned as follows: road density (0.4), stream density (0.3), slope (0.2) and vegetation (0.1). This landscape-base model was modified by climatic conditions to assess the importance of climate to WNV risk. Human case data at the zip code level were used to validate modeling results. All models were summarized by zip codes for interpretation and model validation. For all models, estimated risk was higher for zip codes with at least one human case than for zip codes where no human cases were recorded. Overall median measure of risk by zip code indicated that 67% of human cases occurred in the high-risk category. CONCLUSION: Modeling results indicated that dead bird occurrences are correlated with human WNV risk and can facilitate the assessment of environmental variables that contribute to that risk. Each variable's importance in GIS-based risk predictions was assigned deterministically. Our models indicated non-uniform distribution of risk across the state and showed elevated risk in urban and as well as rural areas. Model limitations include resolution of human data, zip code aggregation issues, and quality/availability of vegetation and stream density layers. Our approach verified that WNV risk can be modeled at the state level and can be modified for risk predictions of other vector-borne diseases in varied ecological regions.
Descriptors: disease outbreaks, environment, geographic information systems, models, theoretical, West Nile fever epidemiology, West Nile virus isolation and purification, birds, mississippi epidemiology, risk factors, West Nile virus.
Corrigan, R.L., C. Waldner, T. Epp, J. Wright, S.M. Whitehead, H. Bangura, E. Young, and H.G. Townsend (2006). Prediction of human cases of West Nile virus by equine cases, Saskatchewan, Canada, 2003. Preventive Veterinary Medicine 76(3-4): 263-72.
Abstract: In 2003, an outbreak of West Nile virus (WNV) occurred in Saskatchewan, Canada from July to September. One-hundred thirty-three horse cases and 947 human cases were recorded and data were analyzed retrospectively for evidence of clustering to determine if clinical infection in the horse population could be used to estimate human risk of infection with WNV. Kulldorff's scan statistic was used to identify spatial-temporal clusters in both the human and horse cases. In most areas, human clusters were not preceded by horse clusters. In one area, a significant cluster of horse cases preceded human cases by 1 week; however, 1 week does not provide sufficient time for human-health authorities to act and provide advance warning for the public.
Descriptors: disease outbreaks, horse diseases epidemiology, diseases transmission, West Nile fever epidemiology, zoonoses, cluster analysis, horse diseases prevention and control, predictive value of tests, retrospective studies, Saskatchewan epidemiology, space time clustering, time factors, West Nile fever, prevention and control, West Nile fever transmission, West Nile virus isolation and purification.
Deegan, C.S., J.E. Burns, M. Huguenin, E.Y. Steinhaus, N.A. Panella, S. Beckett, and N. Komar (2005). Sentinel pigeon surveillance for West Nile virus by using lard-can traps at differing elevations and canopy cover classes. Journal of Medical Entomology 42(6): 1039-1044.
Abstract: Sentinel pigeons, Columba livia, were installed in lard-can traps at heights of 1.5 m and 7.6-9.1 m within differing canopy cover classes in New York City. Adult mosquitoes were collected weekly from July to October 2002, as were serum samples from each pigeon. Culex pipiens L. and Culex restuans Theobald comprised 97% of mosquitoes collected and were most numerous in canopy-level, forested traps. The West Nile virus (family Flaviviridae, genus Flavivirus, WNV) seroconversion rate was significantly greater for pigeons in canopy-level traps, although seroconversions occurred concurrently with human cases in the city and were of little prognostic value to public health agencies. Our results indicate that sentinel pigeons were most effective for monitoring enzootic transmission of WNV when placed in single-sentinel caging 7.6-9.1 m above ground level.
Descriptors: bird diseases, insect vectors, sentinel surveillance, West Nile fever, New York City, polymerase chain reaction methods, species specificity, trees.
DiMenna, M.A., R.J. Bueno, R.R. Parmenter, D.E. Norris, J.M. Sheyka, J.L. Molina, E.M. LaBeau, E.S. Hatton, and G.E. Glass (2006). Comparison of mosquito trapping method efficacy for West Nile virus surveillance in New Mexico. Journal of the American Mosquito Control Association 22(2): 246-253.
Abstract: As part of the West Nile virus surveillance program for the state of New Mexico, 13 sites along the Rio Grande River were sampled for mosquitoes during spring and summer 2003. We evaluated 3 different trapping procedures for their effectiveness at capturing selected species of mosquitoes. The 3 methods used were a dry ice-baited Centers for Disease Control and Prevention (CDC) light trap set 1.5 m above the ground (standard method), a CDC light trap suspended within the forest canopy, and a gravid trap set on the ground. Thirteen sites were sampled for 10 1-night periods biweekly from May through September. The relative numbers of captured Culex tarsalis, Cx. salinarius, Cx. quinquefasciatus, and Aedes vexans as well as the numbers of total recorded captures of all species were compared for each trapping method. Significant differences were observed for each species by location and by trapping method. Culex tarsalis was most commonly caught in canopy or standard CDC traps, especially in cottonwood bosque. Culex salinarius was found most frequently in association with marshy water, and was most often caught in gravid or standard light traps. Culex quinquefasciatus was captured almost exclusively in gravid traps within urban areas. Aedes vexans was primarily sampled in standard CDC light traps and found most frequently in wooded areas near floodplains. With the exception of Cx. Quinquefasciatus, no species was collected significantly more frequently in gravid or canopy traps than in the standard CDC light trap. Our findings do not support altering the methods currently used in New Mexico, namely, the use of 1.5-m CDC light traps and gravid traps. An increased use of gravid traps seems to be warranted in monitoring urban vector populations (specifically Cx. quinquefasciatus and Cx. salinarius) that may be involved in human transmission.
Descriptors: West Nile virus, ecosystem, New Mexico, population surveillance, mosquitoes.
DiMenna, M.A., R.J. Bueno, R.R. Parmenter, D.E. Norris, J.M. Sheyka, J.L. Molina, E.M. LaBeau, E.S. Hatton, and G.E. Glass (2006). Emergence of West Nile virus in mosquito (Diptera: Culicidae) communities of the New Mexico Rio Grande Valley. Journal of Medical Entomology 43(3): 594-599.
Abstract: The first appearances of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in New Mexico were reported in late summer to early fall 2002. Several dead birds tested positive for WNV, and 78 equine cases were confirmed. All mosquito pools tested (n = 268) were negative. A statewide surveillance program was launched in May 2003 to study the emergence and spread of this new arbovirus in mosquitoes from the Rio Grande valley. Mosquitoes were trapped at 32 sites along a 750-km stretch of the Rio Grande valley. Sites were trapped for one night either weekly or biweekly, by using CO2-baited CDC light traps and gravid traps. Pools of captured mosquitoes were tested for WNV by reverse transcription-polymerase chain reaction. By mid-July 2003, WNV levels in the mosquito population had reached levels that were detectable by the surveillance program. Positive pools of mosquitoes were found in the Rio Grande valley from mid-July through late September. In total, 75 positive pools were found, from sites throughout the study area. The predominant species infected with WNV in this region were Culex tarsalis (Coquillett) in rural areas, and Culex salinarius (Coquillett) and Culex pipiens quinquefasciatus (Say) in urban areas. There were 202 human cases and 438 equine cases of WNV in New Mexico in 2003, which corresponded well in time with the positive mosquitoes. Our results seemed to be consistent with introduction of WNV in late summer 2002, followed by a period of transmission and amplification cycles between local avian hosts and mosquito vectors.
Descriptors: West Nile virus, horse diseases, insect vectors, New Mexico, seasons, West Nile fever transmission.
Durand, B., G. Dauphin, H. Zeller, J. Labie, I. Schuffenecker, S. Murri, F. Moutou, and S. Zientara (2005). Serosurvey for West Nile virus in horses in southern France. Veterinary Record: Journal of the British Veterinary Association. 157(22): 711-713. ISSN: 0042-4900.
Descriptors: horses, West Nile virus, seroprevalence, surveillance programs, France.
Dusek, R.J., D. Richardson, K.F. Egstad, and D.M. Heisey (2006). Evaluating red-cockaded woodpeckers for exposure to West Nile virus and blood parasites. Southeastern Naturalist 5(3): 561-565. ISSN: 1528-7092.
Descriptors: red cockaded woodpeckers, parasitology, West Nile virus exposure.
Eidson, M., K. Schmit, Y. Hagiwara, M. Anand, P.B. Backenson, I. Gotham, and L. Kramer (2005). Dead crow density and West Nile virus monitoring, New York. Emerging Infectious Diseases 11(9): 1370-1375. ISSN: 1080-6040.
Abstract: New York State used the health commerce system to monitor the number of West Nile virus (WNV) human disease cases and the density of dead crows. In each year from 2001 to 2003 and for the 3 years combined, persons living in New York counties (excluding New York City) with elevated weekly dead crow densities (above a threshold value of 0.1 dead crows per square mile) had higher risk (2.0-8.6 times) for disease caused by WNV within the next 2 weeks than residents of counties reporting fewer dead crows per square mile. This type of index can offer a realtime, relatively inexpensive window into viral activity in time for prevention and control. Changes in reporting, bird populations, and immunity may require that thresholds other than 0.1 be used in later years or in other areas.
Descriptors: corvus, viral diseases, West Nile virus, mortality rate as index for use in human disease monitoring, evaluation, transmission of viruses, mortality, New York.
Elizondo Quiroga, D., C.T. Davis, I. Fernandez Salas, R. Escobar Lopez, D.V. Olmos, L.C.S. Gastalum, M.A. Acosta, A. Elizondo Quiroga, J.I. Gonzalez Rojas, J.F.C. Cordero, H. Guzman, A.T. da Rosa, B.J. Blitvich, A.D. Barrett, B.J. Beaty, and R.B. Tesh (2005). West Nile virus isolation in human and mosquitoes, Mexico. Emerging Infectious Diseases 11(9): 1449-1452. ISSN: 1080-6040.
Abstract: West Nile virus has been isolated for the first time in Mexico, from a sick person and from mosquitoes (Culex quinquefasciatus). Partial sequencing and analysis of the 2 isolates indicate that they are genetically similar to other recent isolates from northern Mexico and the western United States.
Descriptors: Culex quinquefasciatus, human hosts, viral diseases, West Nile virus, new host record and pathogen characterization, Mexico, Nuevo Leon, Pesqueria Municipality, Ejido Francisco Villa.
Farfan Ale, J.A., B.J. Blitvich, N.L. Marlenee, M.A. Lorono Pino, F. Puerto Manzano, J.E. Garcia Rejon, E.P. Rosado Paredes, L.F. Flores Flores, A. Ortega Salazar, J. Chavez Medina, J.C. Cremieux Grimaldi, F. Correa Morales, G. Hernandez Gaona, J.F. Mendez Galvan, and B.J. Beaty (2006). Antibodies to West Nile virus in asymptomatic mammals, birds, and reptiles in the Yucatan Peninsula of Mexico. American Journal of Tropical Medicine and Hygiene 74(5): 908-914. ISSN: 0002-9637.
Abstract: Surveillance for evidence of West Nile virus (WNV) infection in taxonomically diverse vertebrates was conducted in the Yucatan Peninsula of Mexico in 2003 and 2004. Sera from 144 horses on Cozumel Island, Quintana Roo State, 415 vertebrates (257 birds, 52 mammals, and 106 reptiles) belonging to 61 species from the Merida Zoo, Yucatan State, and 7 farmed crocodiles in Ciudad del Carmen, Campeche State were assayed for antibodies to flaviviruses. Ninety (62%) horses on Cozumel Island had epitope-blocking enzyme-linked immunosorbent assay (ELISA) antibodies to flaviviruses, of which 75 (52%) were seropositive for WNV by plaque reduction neutralization test (PRNT). Blocking ELISA antibodies to flaviviruses also were detected in 13 (3%) animals in the Merida Zoo, including 7 birds and 2 mammals (a jaguar and coyote) seropositive for WNV by PRNT. Six (86%) crocodiles in Campeche State had PRNT-confirmed WNV infections. All animals were healthy at the time of serum collections and none had a history of WNV-like illness.
Descriptors: vertebrata, viral diseases, West Nile virus, prevalence of antibodies in asymptomatic individuals, immune response, antibodies, against viral disease, prevalence in asymptomatic individuals, Mexico, Yucatan Peninsula, prevalence of antibodies against viral disease in asymptomatic individuals.
Gibbs, S.E., A.E. Ellis, D.G. Mead, A.B. Allison, J.K. Moulton, E.W. Howerth, and D.E. Stallknecht (2005). West Nile virus detection in the organs of naturally infected blue jays (Cyanocitta cristata). Journal of Wildlife Diseases 41(2): 354-362.
Abstract: Blue jays (Cyanocitta cristata) are an effective indicator species for West Nile virus (WNV) and may be regionally important in surveillance efforts. The sites of WNV replication and sensitivity of virus detection techniques are undefined for blue jays. The objectives of this study were to describe the gross and microscopic pathology associated with natural WNV infection in blue jays, as well as determine the most appropriate tissues to be used for virus isolation, reverse transcription-nested polymerase chain reaction, and immunohistochemistry (IHC) techniques. Blue jays were collected in Georgia, USA, between May and September 2001. Initial screening by virus isolation indicated that 36 of 59 blue jays chosen for evaluation were WNV positive. From this group, 20 positive and five negative birds were chosen to compare virus detection techniques. Six positive and five negative birds were selected for histopathology examination. Splenomegaly and poor body condition were the most consistent gross findings among positive birds. The most consistent histopathologic findings in the tissues of WNV-positive blue jays were mononuclear leukocytosis and epicarditis/myocarditis. Brain, heart, and lung had the highest viral titers, and WNV antigen was most often detected by IHC in heart, kidney, liver, and lung. Reverse transcription-nested polymerase chain reaction proved to be the most sensitive diagnostic test applied in this study irrespective of the tissue type. Brain tissue could be used effectively for both virus isolation and RT-nPCR, and this tissue is simple to remove and process. The success of IHC is highly dependent on tissue selection, and the use of multiple tissues including heart, kidney, liver, or lung is recommended.
Descriptors: blue jays, Cyanocitta cristata, WNV indicator species, disease surveillance, virus detection techniques, immunohistochemistry techniques (IHC), tissue selection, heart, kidney, lung, liver.
Gibbs, S.E., D.M. Hoffman, L.M. Stark, N.L. Marlenee, B.J. Blitvich, B.J. Beaty, and D.E. Stallknecht (2005). Persistence of antibodies to West Nile virus in naturally infected rock pigeons (Columba livia). Clinical and Diagnostic Laboratory Immunology 12(5): 665-667.
Abstract: Wild caught rock pigeons (Columba livia) with antibodies to West Nile virus were monitored for 15 months to determine antibody persistence and compare results of three serologic techniques. Antibodies persisted for the entire study as detected by epitope-blocking enzyme-linked immunosorbent assay and plaque reduction neutralization test. Maternal antibodies in squabs derived from seropositive birds persisted for an average of 27 days.
Descriptors: viral blood antibodies, West Nile fever, West Nile virus transmission, wild animals, disease transmission, enzyme-linked immunosorbent assay, plaque assay.
Gibbs, S.E., A.B. Allison, M.J. Yabsley, D.G. Mead, B.R. Wilcox, and D.E. Stallknecht (2006). West Nile virus antibodies in avian species of Georgia, USA: 2000-2004. Vector Borne and Zoonotic Diseases 6(1): 57-72. ISSN: 1530-3667.
Abstract: West Nile virus (WNV) was first isolated in the state of Georgia in the summer of 2001. As amplifying hosts of WNV, avian species play an important role in the distribution and epidemiology of the virus. The objective of this study was to identify avian species that are locally involved as potential amplifying hosts of WNV and can serve as indicators of WNV transmission over the physiographic and land use variation present in the southeastem United States. Avian serum samples (n = 14,077) from 83 species of birds captured throughout Georgia during the summers of 2000-2004 were tested by a plaque reduction neutralization test for antibodies to WNV and St. Louis encephalitis virus. Over the 5-year period, WNV-neutralizing antibodies were detected in 869 (6.2%) samples. The WNV seroprevalence increased significantly throughout the study and was species dependent. The highest antibody prevalence rates were detected in rock pigeons (Columba livia), northern cardinals (Cardinalis cardinalis), common ground doves (Columbina passerina), grey catbirds (Deumetella carolinensis), and northern mockingbirds (Mimus polyglottos). Northem cardinals, in addition to having high geometric mean antibody titers and seroprevalence rates, were commonly found in all land use types and physiographic regions. Rock pigeons, common ground doves, grey catbirds, and northern mockingbirds, although also having high seroprevalence rates and high antibody titers against WNV, were more restricted in their distribution and therefore may be of more utility when attempting to assess exposure rates in specific habitat types. Of all species tested, northern cardinals represent the best potential avian indicator species for widespread serologic-based studies of WNV throughout Georgia due to their extensive range, ease of capture, and high antibody rates and titers. Due to the large geographic area covered by this species, their utility as a WNV sentinel species may include most of the eastern United States.
Descriptors: aves, viral diseases, West Nile virus, host records and prevalence, Georgia, USA, viral disease.
Godhardt, J.A., K. Beheler, M.J. O'Connor, T.J. Whyte, E.S. Reisdorf, S.J. Ubl, P.N. Bochsler, and K.L. Toohey Kurth (2006). Evaluation of antigen-capture ELISA and immunohistochemical methods for avian surveillance of West Nile virus. Journal of Veterinary Diagnostic Investigation 18(1): 85-89.
Abstract: Accurate detection of West Nile virus (WNV) in corvids is essential for monitoring the spread of virus during the mosquito season. Viremia in corvids is very high, with titers approaching 10(8) viral particles/ml. In the presence of such marked viremia, the sensitivity of real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis is unnecessary, and more cost-effective methods should be assessed. To this end, antigen-capture ELISA (ACE) and immunohistochemical (IHC) assays were evaluated. Skin, cloacal swab specimens, and feathers from corvids were tested by use of ACE, and results were compared with results obtained from use of real-time RT-PCR analysis. Of the 3 sample types, skin gave the best sensitivity (98%) and specificity (100%). Skin, brain, kidney, and spleen from corvids were analyzed by IHC, and results were compared with real-time RT-PCR results. Kidney and spleen were more often positive by use of IHC than were brain and skin tissue; however, IHC did not perform as well as ACE in the identification of virus-positive birds. Results of this study support the use of a skin sample in an ACE format as an effective surveillance method for corvids.
Descriptors: West Nile virus, ELISA, avian surveillance, antigen capture, evaluation, immunohistochemical methods, accurate detection.
Gu, W., R. Lampman, N. Krasavin, R. Berry, and R. Novak (2006). Spatio-temporal analyses of West Nile virus transmission in culex mosquitoes in northern Illinois, USA, 2004. Vector Borne and Zoonotic Diseases 6(1): 91-98. ISSN: 1530-3667.
Abstract: After a severe outbreak of West Nile virus (WNV) in Cook County, Illinois, in 2002, detections of WNV in mosquitoes were frequent across the state in the following years despite small numbers of human cases. We conducted a spatio-temporal analysis of Culex (subgenus Culex) mosquitoes collected in 2004 in three mosquito abatement districts (MAD) in Cook County by calculating monthly estimates of mosquito density, prevalence of infected mosquitoes, and exposure intensity, which in turn is a product of mosquito density and infection rates. Mosquito infections were detected early at three sites in late May and were widely detected throughout the three MADs in the summer with infection rates as high as 13 per 1000 in August. Exposure intensities were higher at sites adjacent to the Des Plaines River, especially in August and September. The aggregated pattern of WNV transmission along the river might be related to the existence of substantial forest preserves and wetlands that might produce ecological conditions favorable for mosquito proliferation and interactions between mosquitoes and birds.
Descriptors: West Nile virus, culex mosquitoes, infection rate, wetlands, birds, prevalence, ecological conditions.
Hull, J., A. Hull, W. Reisen, Y. Fang, and H. Ernest (2006). Variation of West Nile virus antibody prevalence in migrating and wintering hawks in central California. Condor 108(2): 435-439. ISSN: 0010-5422.
Abstract: To assess the extent of West Nile virus (WNV) exposure of migrating (Marin Headlands) and wintering (Central Valley) hawks in California, plasma from 271 Red-tailed Hawks (Buteo jamaicensis), 19 Red-shouldered Hawks (B. lineatus), and 30 Cooper's Hawks (Accipiter cooperii) was tested for WNV antibodies during the winter of 2004-2005. WNV antibodies were found in 5% of migrating and 15% of wintering Red-tailed Hawks, 20% of migrating and 58% of wintering Red-shouldered Hawks, and 13% of migrating Cooper's Hawks. No individuals demonstrated visible signs of WNV illness. Red-tailed Hawks that tested positive for WNV antibodies displayed no difference from Red-tailed Hawks without WNV antibodies in weight to wing chord ratio or white blood cell counts. In the Central Valley, WNV antibodies were significantly more prevalent in Red-shouldered Hawks than in Red-tailed Hawks. Significantly more Red-tailed Hawks sampled on wintering grounds tested positive for WNV antibodies than Red-tailed Hawks sampled during migration.
Descriptors: Accipiter cooperii, Buteo jamaicensis, Buteo lineatus, migration, viral diseases, West Nile virus, antibody prevalence, temporal variation, migrating and wintering individuals, immune response, viral disease antibody prevalence, California, central.
Language of Text: English, Spanish.
Johnson, G.D., M. Eidson, K. Schmit, A. Ellis, and M. Kulldorff (2006). Geographic prediction of human onset of West Nile virus using dead crow clusters: An evaluation of year 2002 data in New York State. American Journal of Epidemiology 163(2): 171-180.
Abstract: The risk of becoming a West Nile virus case in New York State, excluding New York City, was evaluated for persons whose town of residence was proximal to spatial clusters of dead American crows (Corvus brachyrhynchos). Weekly clusters were delineated for June-October 2002 by using both the binomial spatial scan statistic and kernel density smoothing. The relative risk of a human case was estimated for different spatial-temporal exposure definitions after adjusting for population density and age distribution using Poisson regression, adjusting for week and geographic region, and conducting Cox proportional hazards modeling, where the week that a human case was identified was treated as the failure time and baseline hazard was stratified by region. The risk of becoming a West Nile virus case was positively associated with living in towns proximal to dead crow clusters. The highest risk was consistently for towns associated with a cluster in the current or prior 1-2 weeks. Weaker, but positive associations were found for towns associated with a cluster in just the 1-2 prior weeks, indicating an ability to predict onset in a timely fashion.
Descriptors: bird diseases, epidemiology, crows, West Nile fever, cluster analysis, disease reservoirs, New York, population surveillance, proportional hazards models, West Nile virus isolation and purification.
Jozan, M., R. Evans, J. Webb, R. Cummings, S. Bennett, R. Hall, J. Nevarez, J. Weir, and K. De Collibus (2005). Monitoring of wild bird populations for arbovirus surveillance and new issued [issues] raised by the recent introduction of west Nile virus in Southern Carolina. Arbovirus Research in Australia 9: 169-176. ISSN: 0725-4989.
Descriptors: aves, viral diseases, arboviruses including West Nile virus, monitoring to detect presence and prevalence, California, south, monitoring to detect presence and prevalence of arboviruses including West Nile virus.
Kile, J.C., N.A. Panella, N. Komar, C.C. Chow, A. MacNeil, B. Robbins, and M.L. Bunning (2005). Serologic survey of cats and dogs during an epidemic of West Nile virus infection in humans. Journal of the American Veterinary Medical Association 226(8): 1349-1353.
Abstract: OBJECTIVE: To estimate West Nile virus (WNV) infection rates, assess environmental variables that correlated with seropositivity in dogs and cats, and assess whether pets should be considered as possible sentinels for WNV and therefore of potential human exposure. DESIGN: Cross-sectional serosurvey. ANIMALS: 442 dogs and 138 cats. PROCEDURE: Serum samples were screened for seropositivity against WNV by use of the plaque reduction neutralization test. RESULTS: 116 (26%) dogs and 13 (9%) cats yielded positive results. The odds of seropositivity against WNV for outdoor-only family dogs were almost 19 times as great as those for indoor-only family dogs and almost twice as great for stray dogs as for family dogs. Family dogs not receiving heartworm medication were 2.5 times as likely to yield positive results for antibodies against WNV as family dogs receiving heartworm medication. CONCLUSIONS AND CLINICAL RELEVANCE: Seropositivity was greater for outdoor family dogs than for indoor family dogs. Further investigation of the potential use of stray dogs as sentinel indicators for WNV infection and the potential risk of human exposure is warranted.
Descriptors: infection rates, seropositivity, dogs, cats, sentinel animals, West Nile virus, serosurveys, potential risk, human exposure, transmission of disease.
Komar, O., M.B. Robbins, G.G. Contreras, B.W. Benz, K. Klenk, B.J. Blitvich, N.L. Marlenee, K.L. Burkhalter, S. Beckett, G. Gonzalvez, C.J. Pena, A.T. Peterson, and N. Komar (2005). West Nile virus survey of birds and mosquitoes in the Dominican Republic. Vector Borne and Zoonotic Diseases 5(2): 120-126. ISSN: 1530-3667.
Abstract: We report West Nile virus (WNV) activity from a new area on Hispaniola, in the vicinity of Monte Cristi National Park in northwest Dominican Republic. Specific anti-WNV antibodies were detected in 12 of 58 (21%) resident birds sampled in March 2003, representing six species in the orders Cuculiformes (cuckoos), Strigiformes (owls), and Passeriformes (song birds). This seroprevalence is the highest reported from any site in the Caribbean Basin. Virus was not detected in any mosquitoes or tissues from bird specimens. Testing of 20 sick or dead birds was negative for WNV. Undetermined flavivirus antibodies were detected in four resident birds at Monte Cristi, as well as in five resident birds at Sierra de Baoruco National Park in southwest Dominican Republic. These data suggest that an unidentified flavivirus, as well as WNV, is active in the Dominican Republic.
Descriptors: bird diseases, songbirds, West Nile fever, West Nile virus, viral analysis, disease reservoirs, Dominican Republic, enzyme linked immunosorbent assay, flavivirus, seroepidemiologic studies.
Korves, C.T., S.J. Goldie, and M.B. Murray (2006). Blood screening for west nile virus: the cost-effectiveness of a real-time, trigger-based strategy. Clinical Infectious Diseases 43(4): 490-493.
Abstract: Previous studies have demonstrated that universal blood screening for West Nile virus is not cost-effective. A newly proposed, real-time, trigger-based screening strategy was analyzed and was also shown to be not cost-effective. These results were highly sensitive to pricing of screening assays.
Descriptors: mass screening economics, West Nile fever diagnosis, West Nile virus isolation and purification, cost-benefit analysis.
Kronenwetter Koepel, T.A., J.K. Meece, C.A. Miller, and K.D. Reed (2005). Surveillance of above- and below-ground mosquito breeding habitats in a rural midwestern community: baseline data for larvicidal control measures against West Nile Virus vectors. Clinical Medicine and Research 3(1): 3-12.
Abstract: BACKGROUND: Mosquitoes in the genus Culex are thought to play a major role as vectors in the transmission cycle of West Nile virus (WNV) and other arboviruses in the United States. Effective control of mosquitoes through larviciding and adulticiding is expensive for communities and should be guided by reliable surveillance data on the distribution of mosquito breeding habitats. However, few small to medium sized cities in rural areas of the midwestern United States have this type of baseline information available. OBJECTIVE: During the summer of 2004, we investigated the characteristics of Culex and other mosquito-breeding habitats in a rural central Wisconsin community with a population of approximately 19,000. Such baseline information will aid in the development of rational strategies to control mosquito populations and prevent human exposure to WNV and other mosquito-transmitted viruses. METHODS: Mosquito larvae were collected and identified weekly from 14 below-ground storm water catch basins and 10 above-ground standing water sites distributed throughout the community. Collection began June 4, 2004 and continued through September 24, 2004. For each collection site the primary and adjacent land use patterns were determined. RESULTS: Over the study period, 1,244 larvae were collected from catch basins; 94% were Culex species. Breeding activity was first detected in early July. Peak breeding was observed during a period of several weeks when average daily temperatures were at the maximum observed and rainfall had declined. Organically enriched catch basins in low intensity urban sites adjacent to forests and wetlands were found to be more productive breeding habitats compared to catch basins having little organic debris located in isolated high intensity urban sites. Above-ground standing water sites produced 1,504 larvae; 66% of which were Culex species. Flood control ditches and permanent wetlands with stagnant water were most productive, while ditches with moving water were least productive habitats. Larvae were produced earlier in the season by above-ground sites than were produced by catch basins. However, larvae production was more variable in above-ground sites since half the sites became dry at some point during the study period. CONCLUSION: The observed differences in Culex larvae production based on the variables of habitat-type, temperature, and precipitation support the need for ongoing surveillance in communities to guide public health officials in planning for and prioritizing mosquito control efforts.
Descriptors: Culex, insect vectors, mosquito control, West Nile Virus, breeding environment, insect control methods, rain, rural population, seasons, temperature, time factors, water, weather, West Nile fever prevention and control, Wisconsin.
Lee, B.Y. and B.J. Biggerstaff (2006). Screening the United States blood supply for West Nile Virus: A question of blood, dollars, and sense. PLoS Medicine 3(2): E99.
Descriptors: mass screening, West Nile fever, blood bank standards, blood donors, blood transfusion, cost of illness, cost-benefit analysis, health policy, seasons, specimen handling.
Notes: Comment On: PLoS Med. 2006 Feb;3(2):E21.
Lefrancois, T., B.J. Blitvich, J. Pradel, S. Molia, N. Vachiery, and D. Martinez (2006). West nile virus in guadeloupe: introduction, spread, and decrease in circulation level: 2002-2005. Annals of the New York Academy of Sciences 1081: 206-215. ISSN: 0077-8923.
Abstract: In July 2002, a surveillance system was implemented on Guadeloupe to detect for the potential introduction and monitor the spread of West Nile virus (WNV). From 2002 to 2004, equines and chickens were serologically assayed for antibodies to WNV by IgG and IgM enzyme-linked immunosorbent assay (ELISA), epitope-blocking ELISA, and plaque reduction neutralization tests. After introduction, probably through migratory birds at the end of 2001, many seroconversions occurred between July and October 2002 resulting in a high seroprevalence (19.3%) in equines in 2003. WNV circulation levels decreased dramatically in 2003 and 2004 as assessed by the absence of seroconversion in equine and the very low prevalence in chickens. This decrease coincided with a 7-month drought that presumably caused a decrease in vector populations. In 2005, a sentinel survey was implemented in equines and chickens placed in areas at high risk and the very low rate of seroconversion (1 equine out of 106, no chicken) demonstrated that WNV circulation is now occurring at a very low level.
Descriptors: West Nile virus, equines, chickens, antibodies, serological assay, ELISA, birds, vector populations.
Liu, R., J. Shuai, J. Wu, and H. Zhu (2006). Modeling spatial spread of West Nile virus and impact of directional dispersal of birds. Mathematical Biosciences and Engineering 3(1): 145-160. ISSN: 1547-1063.
Descriptors: West Nile virus spread, modeling, bird dispersal, disease transmission, spatial spread model, long range dispersal patterns.
Lukacik, G., M. Anand, E.J. Shusas, J.J. Howard, J. Oliver, H. Chen, P.B. Backenson, E.B. Kauffman, K.A. Bernard, L.D. Kramer, and D.J. White (2006). West Nile virus surveillance in mosquitoes in New York State, 2000-2004. Journal of the American Mosquito Control Association 22(2): 264-271.
Abstract: A West Nile virus (WNV) surveillance system was created and implemented in New York State (NYS) in 2000 and described previously (White et al. 2001). We examine and evaluate the results of mosquito and virus surveillance for 2000 through 2004 exclusive of New York City. Forty-nine counties submitted 1,095,426 mosquitoes in 35,280 pools for WNV assay. Specimens of 47 species were tested, with Culex species accounting for 47.6% of all pools tested. WNV was detected in 814 pools from 10 species, with combined Culex pipiens/Culex restuans pools accounting for 90.8% of all detections. Pools submitted from gravid traps were 5.7 times more likely to be positive than submissions from carbon dioxide-baited light traps. Most human WNV cases resided in counties that conducted mosquito surveillance. Local health departments' use of mosquito surveillance information often led to an enhanced disease prevention response. In NYS, Cx. pipiens/Cx. restuans groups are most likely vectors of WNV. Future efforts to improve system efficacy are discussed.
Descriptors: Culicidae virology, West Nile virus, Aedes virology, Culex sp., New York, Ochlerotatus, population surveillance, seasons.
Morgan, D. (2006). Control of arbovirus infections by a coordinated response: West Nile Virus in England and Wales. FEMS Immunology and Medical Microbiology 48(3): 305-312.
Abstract: Although there is no recognized transmission of human arboviral infections in the UK, concerns about the possible spread of West Nile virus (WNV) have precipitated coordinated activities around both surveillance and response. The Department of Health has chaired a UK WNV task force since the end of 2000. This is a multidisciplinary group of senior representatives from Agencies and Government Departments involved in human and animal health, entomology and academic departments. Activities include surveillance for WNV infections in humans, and in dead birds, mosquitoes and horses. All have been negative for WNV. A WNV contingency plan was produced in 2004, and this could be used as a generic plan for an effective and coordinated response in the event of the emergence of a new vector-borne zoonotic infection.
Descriptors: West Nile virus surveillance, task force, dead birds, horses, humans, mosquitoes, contingency plan.
Murphy, T.D., J. Grandpre, S.L. Novick, S.A. Seys, R.W. Harris, and K. Musgrave (2005). West Nile virus infection among health-fair participants, Wyoming 2003: Assessment of symptoms and risk factors. Vector Borne and Zoonotic Diseases 5(3): 246-251. ISSN: 1530-3667.
Abstract: Wyoming experienced heavy West Nile virus (WNV) activity for the first time in 2003 and the area hardest hit was Goshen County. Little was known about the epidemiology of WNV in this region. This study describes the symptomatology of WNV and the association between certain behaviors and infection in Goshen County. Study participants were recruited from attendees of a health-fair sponsored by a local hospital, held October 1-3, 2003. A blood sample for WNV testing was obtained from each participant, and participants completed a questionnaire seeking information about the presence of specified symptoms consistent with WNV infection and risk factors possibly associated with infection. The samples were tested for anti-WNV IgM and IgG at the Wyoming Public Health Laboratory. Eight-hundred sixty-nine residents of Goshen County participated, and 122 (14.0%) were seropositive for anti-WNV IgM or IgG. Sixty (59.4%) of 101 persons seropositive for anti-WNV IgM experienced at least one symptom in the previous 4 months consistent with WNV infection, compared with 323 (43.2%) of 747 seronegative persons, resulting in an attributable risk of WNV seropositivity of 16.2%. Of the many symptoms queried, muscle aches (OR 2.63, 95% CI 1.69-4.09), skin rash (OR 6.35, 95% CI 3.74-10.80), fever (OR 2.56, 95% Cl 1.50-4.36), and muscle weakness (OR 2.33, 95% CI 1.34-4.02) were significantly associated with seropositivity on univariate analysis. By multivariate analysis, only skin rash remained significant. Risk factor analysis showed those spending > or =3 hours outside per day were more likely to be seropositive than those spending less time outside per day ( p < 0.05). This study corroborates the belief that a minority of persons infected with WNV develop symptoms attributable to WNV, and also demonstrates that some symptoms are more significantly associated with infection than others.
Descriptors: viral blood antibodies, West Nile fever, exanthema, health surveys, blood immunoglobulin G, blood immunoglobulin M, muscle weakness, risk factors, seroepidemiologic studies, West Nile virus, Wyoming.
Murtagh, B., Y. Wadia, G. Messner, P. Allison, Y. Harati, and R. Delgado (2005). West Nile virus infection after cardiac transplantation. Journal of Heart and Lung Transplantation 24(6): 774-776.
Abstract: West Nile virus is a mosquito-borne RNA Flavivirus infection transmitted to humans and other vertebrates, mainly by the Culex species of mosquito. Since the mid-1990s, the frequency and apparent clinical severity of West Nile virus outbreaks have increased. We report the case of a patient who developed West Nile virus encephalitis shortly after undergoing cardiac transplantation. Clinicians should be aware of the possibility of West Nile virus infection in transplant recipients and in patients receiving blood transfusions.
Descriptors: blood transfusion, adverse effects, heart transplantation, West Nile fever etiology, middle aged humans.
Naugle, D., C. Aldridge, B. Walker, K. Doherty, M. Matchett, J. McIntosh, T. Cornish, and M. Boyce (2005). West Nile virus and sage-grouse: What more have we learned? Wildlife Society Bulletin. 33(2): 616-623. ISSN: 0091-7648.
Descriptors: Centrocercus urophasianus, grouse, West Nile virus, mortality, surveys, Wyoming, Montana, Alberta, Colorado, California.
Ohajuruka, O.A., R.L. Berry, S. Grimes, and S. Farkas (2005). West Nile Virus detection in kidney, cloacal, and nasopharyngeal specimens. Emerging Infectious Diseases 11(9): 1437-1439. ISSN: 1080-6040 .
Abstract: We compared kidney tissue samples and cloacal and nasopharyngeal swab samples from field-collected dead crows and blue jays for West Nile virus surveillance. Compared to tissue samples, 35% more swab samples were false negative. Swab samples were usually positive only when the corresponding tissue sample was strongly positive.
Descriptors: cloaca, crow, kidney, nasopharynx, West Nile virus isolation and purification, false negative reactions, linear models, Ohio, population surveillance methods, reverse transcriptase polymerase chain reaction.
Orme Zavaleta, J., J. Jorgensen, B. D'Ambrosio, E. Altendorf, and P.A. Rossignol (2006). Discovering spatio-temporal models of the spread of West Nile virus. Risk Analysis 26(2): 413-422.
Abstract: Emerging infectious diseases are characterized by complex interactions among disease agents, vectors, wildlife, humans, and the environment. Since the appearance of West Nile virus (WNV) in New York City in 1999, it has infected over 8,000 people in the United States, resulting in several hundred deaths in 46 contiguous states. The virus is transmitted by mosquitoes and maintained in various bird reservoir hosts. Its unexpected introduction, high morbidity, and rapid spread have left public health agencies facing severe time constraints in a theory-poor environment, dependent largely on observational data collected by independent survey efforts and much uncertainty. Current knowledge may be expressed as a priori constraints on models learned from data. Accordingly, we applied a Bayesian probabilistic relational approach to generate spatially and temporally linked models from heterogeneous data sources. Using data collected from multiple independent sources in Maryland, we discovered the integrated context in which infected birds are plausible indicators for positive mosquito pools and human cases for 2001 and 2002.
Descriptors: biological models, West Nile fever transmission, Bayesian theorem, birds, disease outbreaks, disease reservoirs, Maryland epidemiology, risk, West Nile virus isolation and purification.
Orton, S.L., S.L. Stramer, and R.Y. Dodd (2006). Self-reported symptoms associated with West Nile virus infection in RNA-positive blood donors. Transfusion 46(2): 272-277.
Abstract: BACKGROUND: In 2003, West Nile virus (WNV) nucleic acid amplification testing (NAT) was implemented to detect potentially infected donors. Of more than 5.3 million donations screened prospectively by the American Red Cross during the epidemic periods of 2003 and 2004, 974 were NAT-reactive and 519 confirmed-positive. A subset of both the confirmed-positive and the false-positive groups was assessed for demographic characteristics, symptoms, and symptom reporting relative to date of donation. STUDY DESIGN AND METHODS: All donors with initial WNV NAT-reactive results were invited to participate in a study that included a demographic, symptom, and date-of-symptom questionnaire. WNV confirmed-positive cases were compared to false-positive controls for comparison of frequency of symptom reporting before, on the day of, and after donation. RESULTS: Enrolled cases and controls were similar in all characteristics except cases were more likely to live in rural areas. Symptoms were reported by 61 percent of cases versus 20 percent of controls, with 74 percent of symptoms reported by cases within the 14 days after donation. The frequency of headache and fever reported together in the 7 days before donation was not significantly different between cases and controls; only the individual frequencies of headache, eye pain, and new rash during this time were significantly different. The most commonly reported symptoms, after adjustment for symptom reporting by controls, were headache, new rash, and generalized weakness; these symptoms were reported by 25 percent of cases. CONCLUSIONS: The demographic characteristics of infected donors reflected the rural nature of the 2003 to 2004 WNV epidemics. This study suggests that asking donors about predonation headache and fever had no detectable contribution to blood safety.
Descriptors: blood donors, West Nile fever diagnosis, West Nile virus, fever, headache, logistic models, mass screening, middle aged humans, multivariate analysis, viral RNA.
Ozkul, A., Y. Yildirim, D. Pinar, A. Akcali, V. Yilmaz, and D. Colak (2006). Serological evidence of West Nile Virus (WNV) in mammalian species in Turkey. Epidemiology and Infection 134(4): 826-829.
Abstract: In this study, the sera collected from a variety of mammalian species (ass-mules, cat, cattle, dog, horse, human and sheep) in 10 representative provinces of Turkey, were surveyed for the presence of neutralizing antibodies to West Nile virus (WNV). Overall, 1 of 40 (2.5%) ass-mules, 4 of 100 (4%) cattle, 43 of 114 (37.7%) dogs, 35 of 259 (13.5%) horses, 18 of 88 (20.4%) humans and 1 of 100 (1%) sheep, tested positive for WNV-neutralizing antibodies. The results indicate that a wide range of mammals are exposed to a West Nile-related virus and this could contribute to the long-term survival of this virus in the absence of overt disease.
Descriptors: animals, viral blood antibodies, West Nile virus isolation and purification, cats, cattle, disease reservoirs, dogs, equidae, seroepidemiologic studies, sheep, Turkey.
Rappole, J.H., B.W. Compton, P. Leimgruber, J. Robertson, D.I. King, and S.C. Renner (2006). Modeling movement of West Nile virus in the Western hemisphere. Vector Borne and Zoonotic Diseases 6(2): 128-139. ISSN: 1530-3667.
Abstract: We modeled West Nile virus (WNV) movement rates and patterns based on a migratory bird agent (the Swainson's Thrush) and a resident bird agent (the House Sparrow), and compared the results of these models with actual movement data to investigate the likelihood that the pattern of WNV outbreaks observed in the New World was consistent with migrant bird-mediated spread, as reported from the Old World. We found that, contrary to Old World patterns, WNV activity in the Western Hemisphere does not seem consistent with movement by infected migrant birds. Instead WNV spread appears best explained by a non-directional movement, perhaps that of dispersing resident birds.
Descriptors: bird disease transmission, West Nile fever, disease outbreaks, biological models, North America, West Nile virus.
Reisen, W.K., C.M. Barker, R. Carney, H.D. Lothrop, S.S. Wheeler, J.L. Wilson, M.B. Madon, R. Takahashi, B. Carroll, S. Garcia, Y. Fang, M. Shafii, N. Kahl, S. Ashtari, V. Kramer, C. Glaser, and C. Jean (2006). Role of corvids in epidemiology of west Nile virus in southern California. Journal of Medical Entomology 43(2): 356-367. ISSN: 0022-2585.
Abstract: The invasion of different southern California landscapes by West Nile virus (WNV) and its subsequent amplification to epidemic levels during 2004 enabled us to study the impact of differing corvid populations in three biomes: the hot Colorado desert with few corvids (Coachella Valley), the southern San Joaquin Valley (Kern County) with large western scrub-jay but small American crow populations, and the cool maritime coast (Los Angeles) with a large clustered American crow population. Similar surveillance programs in all three areas monitored infection rates in mosquitoes, seroconversion rates in sentinel chickens, seroprevalence in wild birds, numbers of dead birds reported by the public, and the occurrence of human cases. Infection rates in Culex tarsalis Coquillett and sentinel chicken seroconversion rates were statistically similar among all three areas, indicating that highly competent mosquito hosts were capable of maintaining enzootic WNV transmission among less competent and widely distributed avian hosts, most likely house sparrows and house finches. In contrast, infection rates in Culex pipiens quinquefasciatus Say were statistically higher in Kern and Los Angeles counties with elevated corvid populations than in Coachella Valley with few corvids. Spatial analyses of dead corvids showed significant clusters near known American crow roosts in Los Angeles that were congruent with clusters of human cases. In this area, the incidence of human and Cx. p. quinquefasciatus infection was significantly greater within corvid clusters than without, indicating their importance in virus amplification and as a risk factor for human infection. In contrast the uniform dispersion by territorial western scrub-jays resulted in a high, but evenly distributed, incidence of human disease in Kern County.
Descriptors: crows, culex mosquitoes, insect vectors, West Nile fever epidemiology, West Nile virus, California, chickens, incidence, population density, population surveillance, sentinel surveillance, zoonoses transmission.
Reisen, W.K., Y. Fang, H.D. Lothrop, V.M. Martinez, J. Wilson, P. O'Connor, R. Carney, B. Cahoon Young, M. Shafii, and A.C. Brault (2006). Overwintering of West Nile virus in southern California. Journal of Medical Entomology 43(2): 344-355. ISSN: 0022-2585.
Abstract: West Nile virus (family Flaviviridae, genus Flavivirus, WNV) invaded southern California dining 2003, successfully overwintered, amplified to epidemic levels, and then dispersed to every county in the state. Although surveillance programs successfully tracked and measured these events, mechanisms that allowed the efficient overwintering and subsequent amplification of WNV have not been elucidated. Our current research provided evidence for three mechanisms whereby WNV may have persisted in southern California during the winters of 2003-2004 and 2004-2005: 1) continued enzootic transmission, 2) vertical transmission by Culex mosquitoes, and 3) chronic infection in birds. WNV was detected in 140 dead birds comprising 32 species, including 60 dead American crows, thereby verifying transmission during the November-March winter period. Dead American crows provide evidence of recent transmission because this species always succumbs rapidly after infection. However, WNV RNA was not detected concurrently in 43,043 reproductively active female mosquitoes comprising 11 species and tested in 1,258 pools or antibody in sera from 190 sentinel chickens maintained in 19 flocks. Although efficient vertical transmission by WNV was demonstrated experimentally for Culex tarsalis Coquillett infected per os, 369 females collected diapausing in Kern County and tested in 32 pools were negative for WNV. Vertical transmission was detected in Culex pipiens quinquefinciatus Say adults reared from field-collected immatures collected from Kern County and Los Angeles during the summer transmission period. Chronic infection was detected by finding WNV RNA in 34 of 82 birds that were inoculated with WNV experimentally, held for >6 wk after infection, and then necropsied. Frequent detection of WNV RNA in kidney tissue in experimentally infected birds >6 wk postinfection may explain, in part, the repeated detection of WNV RNA in dead birds recovered during winter, especially in species such as mourning doves that typically do not die after experimental infection. In summary, our study provides limited evidence to support multiple modes of WNV persistence in southern California. Continued transmission and vertical transmission by Culex p. quinquefasciatus Say seem likely candidates for further study.
Descriptors: aves, viral diseases, West Nile virus, overwintering, transmission of viruses, California, south, viral disease overwintering.
Reisen, W., S. Wheeler, S. Yamamoto, Y. Fang, and S. Garcia (2005). Nesting ardeid colonies are not a focus of elevated West Nile virus activity in southern California. Vector Borne and Zoonotic Diseases 5(3): 258-266. ISSN: 1530-3667.
Abstract: A large nesting colony of Ardeid birds at the Finney-Ramer Wildlife Refuge in Imperial County, California, did not appear to be a focus of West Nile virus (WNV) amplification during the summer of 2004. Blood samples taken during June and July from 155 nestlings of four species of Ardeid birds (cattle egrets, black-crowned night herons, great egrets, and snowy egrets) and five nestling double-crested cormorants yielded a single WNV isolation from a 3-week-old cattle egret. Antibody was detected by enzyme immunoassay from 20 nestlings (13%), 14 (70%) of which were confirmed as positive by plaque reduction neutralization test (PRNT). However, titration end points against WNV and St. Louis encephalitis virus (SLEV) were similar precluding viral identification. The grouping of positives within few nests, highest PRNT titers in youngest birds (<1 weeks of age), the decline of titer with nestling age, and the lack of antibody specificity indicated that antibody may have been acquired maternally and did not represent new infections. Infection rates in Culex tarsalis mosquitoes collected near the Ardeid colony at Ramer Lake (3.1 per 1,000) were statistically similar to rates estimated at the nearby Wister Unit wetlands (5.3 per 1,000) that lacked an Ardeid nesting colony. Black-crowned night heron nestlings experimentally infected with the NY99 strain of WNV produced viremias >5 log10 plaque forming units (PFU)/mL and were considered moderately competent hosts, whereas cattle egret nestlings had viremias that remained <5 log10 PFU/mL and were incompetent hosts.
Descriptors: Ardea alba, Bubulcus ibis, Egretta thula, Nycticorax nycticorax, Phalacrocorax auritus, viral diseases, West Nile virus, nestling infection rate and host competence survey, California, , Imperial County, Finney Ramer Wildlife Refuge.
Rios, J., C.S. Hacker, C.A. Hailey, and R.E. Parsons (2006). Demographic and spatial analysis of West Nile virus and St. Louis encephalitis in Houston, Texas. Journal of the American Mosquito Control Association 22(2): 254-263.
Abstract: This descriptive prevalence study describes the relationships between mosquito density and the presence of arboviruses (in mosquitoes and humans) with various socioeconomic and environmental factors present near the time of teh arbovirus outbreak in Harris County, Texas, in 2002. This study suggests that mosquito density increased if the trap was located in an area with a large number of containers that may inadvertently retain rainwater (P = 0.056). When considering only virus-positive mosquitoes, significant relationships were observed if the trap was located near waste materials (P < 0.001) or near containers that may inadvertently retain rainwater (P = 0.037). Furthermore, the presence of arbovirus activity (in mosquitoes or humans) in a geographic area tended to be associated with the socioeconomic status of the local community. Although the results of socioeconomic comparisons were not significant, they were suggestive, demonstrating an interesting trend. Compared with communities where virus activity was not observed, the socioeconomic status of the arbovirus-positive community was consistently lower. Specifically, results showed that the populations residing in virus-positive census tracts attained less education, earned less income per household, and were more likely to be below the poverty level. In addition, this study found that virus-positive mosquitoes were randomly distributed throughout the study area, whereas severe human infection cases were clustered. Based on the results of this study, we conclude that the health outcome of a local community as it relates to West Nile virus and St. Louis encephalitis is dependent on many factors, including eh socioeconomic and environmental characteristics of the community.
Descriptors: Culicidae virology, St. Louisencephalitis epidemiology, West Nile virus, disease outbreaks, ecosystem, educational status, encephalitis transmission, population surveillance, poverty, socioeconomic factors, Texas.
Roberts, R.S. and I.M. Foppa (2006). Prediction of equine risk of West Nile Virus infection based on dead bird surveillance. Vector Borne and Zoonotic Diseases 6(1): 1-6. ISSN: 1530-3667.
Abstract: Since the introduction of West Nile Virus (WNV) to the United States in 1999, the efficacy of dead bird surveillance for the prediction of human and veterinary WNV infection has been an issue of debate. We utilized South Carolina's Department of Health and Environmental Control surveillance data from 2003 to determine whether dead bird surveillance accurately predicts equine WNV infection on a county level. We adjusted for human population density as a potential confounder of an association between WNV-positive dead bird counts and mammalian WNV risk. We found a strong positive association between avian risk of WNV death and subsequent equine mortality due to WNV in South Carolina even after adjusting for human population density. Sensitivity of dead bird surveillance as a predictor of future equine WNV risk was far superior to mosquito surveillance (95% vs. 9.5%, respectively). A Poisson regression model of the equine WNV rate as a function of WNV-positive dead bird rate, adjusting for population density and taking into account effect modification by population density shows a good fit with the data. Unlike most previous studies, we control for potential confounding of the dead, WNV-positive bird-equine WNV infection association by human population density. Yet, the positive association between dead bird surveillance and equine WNV risk remains strong and statistically significant, indicating that dead bird surveillance remains a valuable tool of WNV surveillance.
Descriptors: aves, pathological techniques, viral disease effect on mortality, dead host surveillance use in disease risk prediction in mammals, viral diseases, West Nile virus, mortality effects, mortality, viral disease effects, South Carolina.
Rockx, B., L. van Asten, C. van den Wijngaard, G.J. Godeke, L. Goehring, H. Vennema, H. van der Avoort, W. van Pelt, and M. Koopmans (2006). Syndromic surveillance in the Netherlands for the early detection of West Nile virus epidemics. Vector Borne and Zoonotic Diseases 6(2): 161-169. ISSN: 1530-3667.
Abstract: West Nile virus (WNV) is an arthropod-borne flavivirus that is endemic in Africa, Europe, and Eastern Asia. The recent introduction and rapid dissemination of the virus in the United States as well as an increase in WNV outbreaks in Europe, has raised concerns for its spread in Europe. A surveillance system was developed to allow timely detection of an introduction of WNV infections in The Netherlands. This program focuses on cases presenting with neurological disease and includes the monitoring of hospital discharge diagnoses, trends in cerebrospinal fluid (CSF) diagnostic requests, laboratory testing of CSF, and monitoring of neurological disease in horses. Retrospective data from the hospital discharge records showed yearly peaks of unexplained meningitis and (meningo)encephalitis in the summer. A total of 781 CSF samples from humans and 71 serum and/or CSF samples from horses presenting with neurological disease of suspected viral etiology tested negative for the presence of specific antibodies to WNV. With a coverage rate of 59% in 2003, the probability that a cluster of five WNV cases presenting with neurological symptoms would have been detected was 99%. We conclude that, from 1999 to 2004, no evidence of WNV infection could be found in either humans or horses in The Netherlands.
Descriptors: cerebrospinal fluid, horse diseases, hospitals statistics, numerical data, sentinel surveillance, West Nile fever, Netherlands, retrospective studies, seasons, West Nile virus isolation and purification.
Sabio, I.J., A.J. Mackay, A. Roy, and L.D. Foil (2006). Detection of West Nile virus RNA in pools of three species of ceratopogonids (Diptera: Ceratopogonidae) collected in Louisiana. Journal of Medical Entomology 43(5): 1020-1022. ISSN: 0022-2585.
Abstract: Light traps were used to collect ceratopogonids in East Baton Rouge parish, Louisiana. In total, 46,496 ceratopogonids were sorted from 4,968 light trap collections from 20 November 2002 through 25 November 2004. Two hundred and nine pools containing specimens of 18 species of Culicoides Latreille, seven pools containing specimens of Atrichopogon Kieffer, and five pools containing specimens of Forcipomyia Meigen were tested for West Nile virus (family Flaviviridae, genus Flavivirus, WNV) RNA using real-time reverse transcriptase polymerase chain reaction. Five out of the 209 pools of Culicoides specimens were positive for WNV RNA.
Descriptors: West Nile virus, detection, trap collection, Culicoides, RNA, reverse transcriptase polymerase chain reaction, Louisiana.
Santaella, J., R. McLean, J.S. Hall, J.S. Gill, R.A. Bowen, H.H. Hadow, and L. Clark (2005). West Nile Virus serosurveillance in Iowa white-tailed deer (1999-2003). American Journal of Tropical Medicine and Hygiene 73(6): 1038-1042. ISSN: 0002-9637.
Abstract: Sera from white-tailed deer (Odocoileus virginianus) were collected in Iowa during the winter months (1999-2003), 2 years before and after West Nile virus (WNV) was first reported in Iowa (2001), and were analyzed for antibodies to WNV. Samples from 1999 to 2001 were antibody negative by blocking enzyme-linked immunosorbent assay (bELISA) and plaque reduction neutralization test (PRNT90). Prevalence derived from bELISA (2002, 12.7%; 2003,11.2%) and WNV PRNT90 (2002, 7.9%; 2003, 8.5%) assays were similar. All samples were negative for antibodies against St. Louis encephalitis virus as determined by PRNT90. Antibodies to flaviviruses were detected by indirect enzyme-linked immunosorbent assay (iELISA) prior to the first WNV cases reported in Iowa (1999-2001) with prevalence ranging from 2.2% to 3.2%, suggesting the circulation of an additional undescribed flavivirus prior to the introduction of WNV into the area. Flavivirus prevalence as determined by iELISA increased in 2002 and 2003 (23.3% and 31.9%, respectively). The increase in prevalence exceeded estimates of WNV prevalence, suggesting that conditions favored general flavivirus transmission (including WNV) during the 2002-2003 epizootic. These data indicate that serologic analysis of deer sera collected from hunter harvests may prove useful for surveillance and evidence of local transmission of WNV and other pathogens and identify white-tailed deer as a species for further studies for host competency.
Descriptors: Odocoileus virginianus, viral diseases, West Nile virus, serosurveillance before and after epizootic, Iowa.
Scheidler, L.C., M.M. Dunphy Daly, B.J. White, D.R. Andrew, N.Z. Mans, and M.C. Garvin (2006). Survey of Aedes triseriatus (Diptera: Culicidae) for Lacrosse encephalitis virus and West Nile virus in Lorain County, Ohio. Journal of Medical Entomology 43(3): 589-593. ISSN: 0022-2585.
Abstract: From June through September 2003, we conducted a survey of female Aedes triseriatus (Say) for infection with La Crosse encephalitis virus (family Bunyaviridae, genus Orthobunyavirus, LACV) and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) at three locations in Lorain County, Ohio. To determine infection rate and seasonal variation of both viruses in the Ae. triseriatus population, Ae. triseriatus were collected weekly by using gravid traps and CO2-baited CDC light traps and tested for virus by using reverse transcriptase polymerase chain reaction. In total, 170 pools comprised of 2,143 females were tested for LACV, of which seven were positive; the maximum likelihood estimate of infection rate combined throughout the season was 3.22/1,000. None of 170 pools comprised of 2,158 females tested for WNV were positive. LACV-positive pools were detected between late July and early September.
Descriptors: West Nile virus isolation and purification, insect vectors, la crosse virus genetics, Ohio, viral RNA analysis, reverse transcriptase polymerase chain reaction, seasons.
Schellenberg, T.L., M.E. Anderson, M.A. Drebot, M.T. Vooght, A.R. Findlater, P.S. Curry, C.A. Campbell, and W.D. Osei (2006). Seroprevalence of West Nile virus in Saskatchewan's Five Hills Health Region, 2003. Canadian Journal of Public Health 97(5): 369-373.
Abstract: BACKGROUND: The Five Hills Health Region of Saskatchewan reported the highest West Nile virus (WNV) case rates in the 2003 outbreak. A serologic and telephone survey was undertaken to assess the seroprevalence of the virus and the knowledge, attitudes and behaviours of the residents. METHODS: Respondents had to be at least 18 years of age, and residents of the Five Hills Health Region between July 1st and September 15th, 2003. Blood samples of respondents were tested at the National Microbiology Laboratory for flavivirus immunoglobulin using a WNV IgG ELISA and plaque reduction neutralization test. Descriptive analyses performed related to respondents' demographics, knowledge, attitudes, behaviours, and seropositivity. WNV infection risk was assessed using odds ratio. RESULTS: There were 619 questionnaire respondents, of whom 501 donated a blood sample. The seroprevalence of WNV in the Five Hills Health Region was 9.98% (95% CI 7.37-12.59%). Seropositivity of rural areas was 16.8% and urban was 3.2%. Most (97%) of participants thought WNV was an important health issue. Forty-eight percent of the participants used insect repellents containing DEET most of the time. There was good knowledge regarding WNV transmission and prevention of the spread of WNV. Rural compared to urban residents were six times more likely to be positive for WNV (OR=6.13, 95% CI 2.82-13.34). INTERPRETATION: This is the highest seroprevalence rate of West Nile virus recorded in North America thus far. Many factors could have influenced this outbreak, such as eco-region, early prolonged hot weather, level of mosquito control programs, urban and rural community differences, and personal protective behaviours.
Descriptors: disease outbreaks, West Nile fever, human attitudes to health, questionnaires, rural health, Saskatchewan, urban health, West Nile virus, blood.
Schweitzer, B.K., W.L. Kramer, A.R. Sambol, J.L. Meza, S.H. Hinrichs, and P.C. Iwen (2006). Geographic factors contributing to a high seroprevalence of West Nile virus-specific antibodies in humans following an epidemic. Clinical and Vaccine Immunology 13(3): 314-318. ISSN: 1556-6811.
Abstract: Sera of 624 blood donors were evaluated to determine seroprevalence of West Nile virus (WNV) antibodies following the 2003 WNV epidemic in Nebraska. Geographic factors contributing to differences in WNV seropositivity were evaluated. The overall prevalence of WNV in Nebraska was higher than reported previously in other U.S. locations (9.5% WNV immunoglobulin G seroprevalence rate), with the highest prevalence identified in the western part of the state (19.7%), followed by the central (13.8%) and the eastern (4.2%) parts. Regions of the state with the highest WNV-positive mosquito rates correlated with the highest human WNV seroprevalence rates. The results showed that both the western and central parts of the state, where mosquito positivity rates were highest, had significantly higher seroprevalence rates than the eastern region. Additional studies are needed to determine whether the high prevalence rates in Nebraska will be reflected in other states and what impact environmental and geographical factors may have on future outbreaks of WNV infection.
Descriptors: viral blood antibodies, disease outbreaks, West Nile fever, West Nile virus, Nebraska, seroepidemiologic studies.
Shuai, J., P. Buck, P. Sockett, J. Aramini, and F. Pollari (2006). A GIS-driven integrated real-time surveillance pilot system for national West Nile virus dead bird surveillance in Canada. International Journal of Health Geographics 5: 17.
Abstract: BACKGROUND: An extensive West Nile virus surveillance program of dead birds, mosquitoes, horses, and human infection has been launched as a result of West Nile virus first being reported in Canada in 2001. Some desktop and web GIS have been applied to West Nile virus dead bird surveillance. There have been urgent needs for a comprehensive GIS services and real-time surveillance. RESULTS: A pilot system was developed to integrate real-time surveillance, real-time GIS, and Open GIS technology in order to enhance West Nile virus dead bird surveillance in Canada.Driven and linked by the newly developed real-time web GIS technology, this integrated real-time surveillance system includes conventional real-time web-based surveillance components, integrated real-time GIS components, and integrated Open GIS components. The pilot system identified the major GIS functions and capacities that may be important to public health surveillance. The six web GIS clients provide a wide range of GIS tools for public health surveillance. The pilot system has been serving Canadian national West Nile virus dead bird surveillance since 2005 and is adaptable to serve other disease surveillance. CONCLUSION: This pilot system has streamlined, enriched and enhanced national West Nile virus dead bird surveillance in Canada, improved productivity, and reduced operation cost. Its real-time GIS technology, static map technology, WMS integration, and its integration with non-GIS real-time surveillance system made this pilot system unique in surveillance and public health GIS.
Descriptors: bird diseases and associated mortality, sentinel surveillance, West Nile fever, automatic data processing methods, Canada, cluster analysis, pilot projects.
Sirigireddy, K.R., G.A. Kennedy, A. Broce, L. Zurek, and R.R. Ganta (2006). High prevalence of west nile virus: a continuing risk in acquiring infection from a mosquito bite. Vector Borne and Zoonotic Diseases 6(4): 351-360. ISSN: 1530-3667.
Abstract: The prevalence of West Nile Virus (WNV) was evaluated by diplex real-time RT-PCR assay for the years 2001-2005 in Culex species of mosquitoes, several species of dead birds, and clinically suspected mammals collected in Kansas. The analysis was performed using a TaqMan-based diplex real-time RT-PCR assay targeted against two regions of the WNV genome, envelope glycoprotein gene and 3' untranslated region. The assay aided in the accurate detection of WNV in mosquitoes at high prevalence for the years 2002-2005. Similarly, high incidence of birds that tested positive for WNV was detected in 2002-2004. WNV positives in mammals by the diplex real rime RT-PCR assay included horses, squirrels, mules, sheep and a mountain goat. Majority of the equine WNV positives were detected only in the year 2002. Sequence analysis of a segment of the envelope glycoprotein gene from 31 randomly selected WNV positive samples revealed variations in six samples at one or two nucleotide positions. The identity of high levels of WNV positives in Kansas parallels the recent reports on the widespread distribution of the virus in the United States. The continued detection of WNV in the mosquitoes is of significant public health concern and calls for continued surveillance and public health activities.
Descriptors: West Nile virus, prevalnce, risk, evaluated, dead birds, mosquitoes, surveillance, public health, distribution.
Stein, K.J. and D.M. Claborn (2005). Telephonic survey of surveillance and control procedures for the mosquito vectors of West Nile virus near naval installations in the Eastern United States. Military Medicine 170(8): 658-662. ISSN: 0026-4075.
Descriptors: West Nile virus, telephone surveillance, control procedures, viral vectors, United States, dead birds, mosquitoes.
Stephen, C., N. Plamondon, and P. Belton (2006). Notes on the distribution of mosquito species that could potentially transmit West Nile virus on Vancouver Island, British Columbia. Journal of the American Mosquito Control Association 22(3): 553-556.
Abstract: We record the spatial and temporal distribution of 8 potential vectors of West Nile virus (WNV) on Vancouver Island in 2003 and 2004. Five species were widely distributed, but the other 3 were restricted to specific larval habitats. Adults were trapped from early April to September. The findings indicate a potential for WNV transmission if the virus arrives on the island. The results extend the published range of 5 mosquito species.
Descriptors: Culicidae virology, West Nile virus, Aedes, Anopheles, British Columbia, insect vectors, larva, population surveillance, West Nile fever transmission.
Stramer, S.L., B. Custer, M.P. Busch, and R.Y. Dodd (2006). Strategies for testing blood donors for West Nile virus. Transfusion 46(12): 2036-2037.
Descriptors: blood donors, West Nile virus, surveillance, strategies, detection, testing.
Sullivan, H., G. Linz, L. Clark, and M. Salman (2006). West Nile virus antibody prevalence in red-winged blackbirds (Agelaius phoeniceus) from North Dakota, USA (2003-2004). Vector Borne and Zoonotic Diseases 6(3): 305-309. ISSN: 1530-3667.
Abstract: This study was designed to explore the role that red-winged blackbirds (Agelaius phoeniceus) may have played in disseminating West Nile virus (WNV) across the United States. Using enzyme-linked immunosorbent assays designed to detect WNV antibodies in avian species we were able to determine the WNV antibody prevalence in a cohort of red-winged blackbirds in central North Dakota in 2003 and 2004. The peak WNV antibody prevalence was 22.0% in August of 2003 and 18.3% in July of 2004. The results of this study suggest that red-winged blackbird migratory populations may be an important viral dispersal mechanism with the ability to spread arboviruses such as WNV across the United States.
Descriptors: West Nile virus, red winged black birds, antibody prevalence, migratory populations, disseminating, disperal, spread.
Tachiiri, K., B. Klinkenberg, S. Mak, and J. Kazmi (2006). Predicting outbreaks: A spatial risk assessment of West Nile virus in British Columbia. International Journal of Health Geographics 5: 21.
Abstract: BACKGROUND: West Nile virus (WNv) has recently emerged as a health threat to the North American population. After the initial disease outbreak in New York City in 1999, WNv has spread widely and quickly across North America to every contiguous American state and Canadian province, with the exceptions of British Columbia (BC), Prince Edward Island and Newfoundland. In this study we develop models of mosquito population dynamics for Culex tarsalis and C. pipiens, and create a spatial risk assessment of WNv prior to its arrival in BC by creating a raster-based mosquito abundance model using basic geographic and temperature data. Among the parameters included in the model are spatial factors determined from the locations of BC Centre for Disease Control mosquito traps (e.g., distance of the trap from the closest wetland or lake), while other parameters were obtained from the literature. Factors not considered in the current assessment but which could influence the results are also discussed. RESULTS: Since the model performs much better for C. tarsalis than for C. pipiens, the risk assessment is carried out using the output of C. tarsalis model. The result of the spatially-explicit mosquito abundance model indicates that the Okanagan Valley, the Thompson Region, Greater Vancouver, the Fraser Valley and southeastern Vancouver Island have the highest potential abundance of the mosquitoes. After including human population data, Greater Vancouver, due to its high population density, increases in significance relative to the other areas. CONCLUSION: Creating a raster-based mosquito abundance map enabled us to quantitatively evaluate WNv risk throughout BC and to identify the areas of greatest potential risk, prior to WNv introduction. In producing the map important gaps in our knowledge related to mosquito ecology in BC were identified, as well, it became evident that increased efforts in bird and mosquito surveillance are required if more accurate models and maps are to be produced. Access to real time climatic data is the key for developing a real time early warning system for forecasting vector borne disease outbreaks, while including social factors is important when producing a detailed assessment in urban areas.
Descriptors: Culex sp., forecasting methods, West Nile virus, British Columbia, geographic information systems (GIS), theoretical models, population density, population dynamics, risk, temperature.
Tilley, P.A., G.A. Zachary, R. Walle, and P.F. Schnee (2005). West Nile virus detection and commercial assays. Emerging Infectious Diseases 11(7): 1154-1155. ISSN: 1080-6040.
Descriptors: viral blood antibodies, blood immunoglobulin M, diagnostic reagent kits, West Nile fever diagnosis, West Nile virus isolation and purification, blood immunoglobulin G, time factors.
Tilley, P.A.G., R. Walle, A. Chow, G.C. Jayaraman, K. Fonseca, M.A. Drebot, J. Preiksaitis, and J. Fox (2005). Clinical Utility of Commercial Enzyme Immunoassays during the Inaugural Season of West Nile Virus Activity, Alberta, Canada. Journal of Clinical Microbiology. 43(9): 4691-4695. ISSN: 0095-1137.
Abstract: West Nile virus (WNV) has spread rapidly across North America, creating a need for rapid and accurate laboratory diagnosis on a large scale. Immunoglobulin M (IgM) capture enzyme immunoassays (EIA) became commercially available in the summer of 2003, but limited data are available on their clinical performance. Consolidated human WNV diagnostic testing for the province of Alberta, Canada, at the public health laboratory permitted a large-scale evaluation of the assays, covering a wide clinical spectrum. Two thousand nine hundred sixty-nine sera were tested, from 2,553 Alberta residents, and 266 cases were identified. Sensitivities of the Focus assay and first-generation Panbio IgM capture EIA were 79 and 80%, respectively. During the first week of illness only 53 to 58% of cases were positive, but sensitivity was 96 to 97% after day 8. Sensitivity for neurological cases was 92% overall. Specificity was high for the Focus kit at 98.9%, but only 82.9% for the first Panbio kit. A positive Focus WNV IgG result with a twofold rise in IgG index was a reliable indicator of acute flavivirus infection (67/67 WNV). Agreement between the IgG test and hemagglutinin inhibition titers in paired sera was at least 82%. Commercial IgM and IgG EIA proved useful for WNV diagnosis, provided follow-up sera were collected after 8 days of illness.
Descriptors: West Nile virus, detection, surveillance, diagnosis, immunoglobulin M, enzyme assays, EIA, Canada.
Vamvakas, E.C., S. Kleinman, H. Hume, and G.D. Sher (2006). The development of West Nile virus safety policies by Canadian blood services: Guiding principles and a comparison between Canada and the United States. Transfusion Medicine Reviews 20(2): 97-109.
Abstract: To address the emerging threat of West Nile virus (WNV) to the blood supply, Canadian Blood Services (CBS) made a series of policy decisions that were either similar to those adopted in the United States or more stringent than policies formulated in the United States at the same time. More stringent Canadian policies included the development of an in-house WNV RNA assay, the stockpiling of frozen plasma components in the winter for transfusion in WNV-affected areas in the summer, a special recruitment campaign for red blood cell collections before the start of the 2003 WNV season, and an inventory exchange (ie, WNV-tested for untested red blood cells) initiated 2 weeks after the onset of WNV screening, as well as the implementation of targeted individual-donation WNV testing on August 2, 2004, in the absence of any positive donors or clinical cases of WNV infection in Canada. The general principles that guided CBS decision making with regard to WNV safety included application of the precautionary principle, harmonization with policies in the United States, a consideration of logistic issues, compliance with Health Canada requests, responsiveness to public expectations about transfusion safety, and transparency in decision making with timely communication to stakeholders. Before implementing WNV blood safety policies, CBS assessed their impact on blood availability. When policies were implemented, data were obtained quickly to ensure that the prior impact assessments were accurate. This review discusses the guiding principles affecting CBS policy development and compares CBS WNV safety policies to policies adopted in the United States.
Descriptors: blood bank standards, blood transfusion safety, West Nile fever prevention and control, West Nile virus, blood specimen collection standards, blood transfusion, Canada, health policy, United States.
Ward, M.P. (2006). Spread of equine West Nile virus encephalomyelitis during the 2002 Texas epidemic. American Journal of Tropical Medicine and Hygiene 74(6): 1090-1095. ISSN: 0002-9637.
Abstract: Using reports of clinical West Nile virus (WNV) encephalomyelitis in Texas equids during 2002, the distribution of disease was analyzed using cluster statistics and spatial modeling to develop hypotheses of disease spread during the first year of its detection. Significant (P < 0.05) clusters of cases reported early during the outbreak were identified in east, northcentral, and north Texas, and significant (P < 0.05) clusters late during the outbreak were detected in central, south, and west Texas. Two counties on the south Texas coast first reported disease significantly (P < 0.05) earlier than their 10 nearest neighboring counties. The estimated incidence of disease was greatest in the high plains of north Texas and in northcentral Texas. Higher rates were also estimated in eastern and southern areas of the Gulf Coast. The spatial and temporal distribution observed indicates that the equine WNV epidemic began in two parts of Texas and spread elsewhere throughout the state. The mechanism of introduction and spread remains speculative.
Descriptors: disease outbreaks, horse diseases, West Nile fever, cluster analysis, geography, statistical models, Texas, zoonoses.
Ward, M.P. (2005). Epidemic West Nile virus encephalomyelitis: A temperature-dependent, spatial model of disease dynamics. Preventive Veterinary Medicine 71(3-4): 253-264.
Abstract: Since first being detected in New York in 1999, West Nile virus (WNV) has spread throughout the United States and more than 20,000 cases of equine WNV encephalomyelitis have been reported. A spatial model of disease occurrence was developed, using data from an outbreak of serologically confirmed disease in an unvaccinated population of horses at 108 locations in northern Indiana between 3 August and 17 October 2002. Daily maximum temperature data were recorded at meteorological stations surrounding the study area. The distribution of the total number of degree-days elapsing between July 4 and the date of diagnosis of each case was best described by a normal distribution (mean=5243 degrees F, S.D.=1047). The days on which the average risk was >25, >50 and >75% were predicted (versus observed) to occur on August 23 (August 9), August 31 (September 2) and September 9 (September 9). The epidemic was predicted to occur 3 days earlier, or 4 days later, than observed if temperatures in the study area were uniformly increased, or decreased, by 5 degrees F, respectively. Maps indicated that WNV encephalomyelitis risk always remained greater in the northwest quadrant of the study area. Since WNV might exist at a hypoendemic level of infection, and occasionally re-emerge as a cause of epidemics in equine populations, by identifying factors that contributed to this epidemic, the potential impact of future epidemics can be reduced. Such studies rely on a GIS framework, availability of meteorological and possibly remotely sensed data and information on host and landscape factors. An early-warning system for WNV transmission in equine populations could be developed.
Descriptors: animal disease outbreaks, horse diseases, West Nile fever, horses, Indiana, statistical models, space-time clustering, West Nile virus.
Ward, M.R., D.E. Stallknecht, J. Willis, M.J. Conroy, and W.R. Davidson (2006). Wild bird mortality and West Nile virus surveillance: biases associated with detection, reporting, and carcass persistence. Journal of Wildlife Diseases 42(1): 92-106. ISSN: 0090-3558.
Abstract: Surveillance targeting dead wild birds, in particular American crows (Corvus brachyrhynchos), plays a critical role in West Nile virus (WNV) surveillance in the United States. Using crow decoy surrogates, detection and reporting of crow carcasses within urban and rural environments of DeKalb County, Georgia were assessed for potential biases that might occur in the county's WNV surveillance program. In each of two replicated trials, during July and September 2003, 400 decoys were labeled with reporting instructions and distributed along randomly chosen routes throughout designated urban and rural areas within DeKalb County. Information-theoretic methods were used to compare alternative models incorporating the effects of area and trial on probabilities of detection and reporting. The model with the best empirical support included the effects of area on both detection and reporting of decoys. The proportion of decoys detected in the urban area (0.605, SE = 0.024) was approximately twice that of the rural area (0.293, SE = 0.023), and the proportion of decoys reported in the urban area (0.273, SE = 0.023) was approximately three times that of the rural area (0.103, SE = 0.028). These results suggest that human density and associated factors can substantially influence dead crow detection and reporting and, thus, the perceived distribution of WNV. In a second and separate study, the persistence and fate of American crow and house sparrow (Passer domesticus) carcasses were assessed in urban and rural environments in Athens-Clarke, Madison, and Oconee counties, Georgia. Two replicated trials using 96 carcasses of each species were conducted during July and September 2004. For a portion of the carcasses, motion sensitive cameras were used to monitor scavenging species visits. Most carcasses (82%) disappeared or were decayed by the end of the 6-day study. Carcass persistence averaged 1.6 days in rural areas and 2.1 days in urban areas. We analyzed carcass persistence rates using a known-fate model framework in program MARK. Model selection based on Akaike's Information Criteria (AIC) indicated that the best model explaining carcass persistence rates included species and number of days of exposure; however, the model including area and number of days of exposure received approximately equal support. Model-averaged carcass persistence rates were higher for urban areas and for crow carcasses. Six mammalian and one avian species were documented scavenging upon carcasses. Dead wild birds could represent potential sources of oral WNV exposure to these scavenging species. Species composition of the scavenger assemblage was similar in urban and rural areas but "scavenging pressure" was greater in rural areas.
Descriptors: aves, ecological techniques, wild bird mortality monitoring and application in West Nile virus surveillance, biases, pathological techniques, viral diseases, West Nile virus, wild bird mortality monitoring application in disease surveillance, mortality, Georgia USA.
Ward, M., D. Stallknecht, J. Willis, M. Conroy, and W. Davidson (2006). Wild bird mortality and West Nile virus surveillance: biases associated with detection, reporting, and carcass persistence. Journal of Wildlife Diseases. 42(1): 92-106. ISSN: 0090-3558.
Descriptors: disease surveillance, Corvus brachyrhynchos, dead animals, Passer domesticus, urban areas, rural areas, disease transmission, mathematical models, Georgia, scavenging.
White, B.J., D.R. Andrew, N.Z. Mans, O.A. Ohajuruka, and M.C. Garvin (2006). West Nile virus in mosquitoes of northern Ohio, 2003. American Journal of Tropical Medicine and Hygiene 75(2): 346-349. ISSN: subcutaneous.
Abstract: From June 19, 2003 to August 18, 2003, we surveyed the mosquitoes of Oberlin, OH, for West Nile Virus (WNV) infection using reverse transcriptase-polymerase chain reaction. A total of 12,055 mosquitoes, representing 17 species or species groups and 4 genera, were collected in gravid traps at seven sites throughout the city, with Culex pipiens/restuans being the most abundant and showing the highest minimum infection rate (MIR) of 0.78. This represents a decrease in WNV enzootic activity from the previous year. Both Cx. pipiens/restuans abundance and MIR increased significantly with date. However, we found no correlation between Cx. pipiens/restuans abundance and MIR.
Descriptors: culex mosquitos, insect vectors, West Nile virus isolation and purification, culicidae classification, Ohio, population density, population surveillance methods, reverse transcriptase polymerase chain reaction methods, time factors, West Nile fever transmission.