Abbassy, MM; Osman, M; Marzouk, AS. West Nile virus (Flaviviridae:Flavivirus) in experimentally infected Argas ticks (Acari:Argasidae). American Journal of Tropical Medicine and Hygiene. 1993 May; 48(5): 726-37. ISSN: 0002-9637.

NAL Call No.: 448.8 Am326

Descriptors: possible insect vector, adult ticks, Argas arboreus, Argas persicus, Argas hermanni, feeding of virus, virus titers, location of virus in ticks, vertical and horizontal transmission studies.

Abstract: To better define the possible role of argasid ticks in the epidemiology of West Nile virus, adult Argas arboreus, A. persicus, and A. hermanni were fed through a membrane on fetal bovine serum containing 10(5.5) 50% tissue culture infective doses (TCID50)/ml of West Nile virus. The virus was detected for three and four days after feeding in A. persicus and A. hermanni, respectively. The virus titers then decreased to undetectable levels in both species. When the infective dose was increased to 10(6.2), virus was detected until days 6 and 8, respectively. In A. arboreus, virus titers in whole tick homogenates reached a peak of 10(4.0) on day 4 postfeeding and remained constant at 10(3.0) after day 6 throughout the 20- or 50-day observation periods. Virus was detected by isolation, indirect fluorescent antibody, and histochemical techniques in the salivary glands, ovaries, synganglia, and coxal fluids. Infected ticks successfully transmitted virus to clean chickens on day 20 postfeeding. No evidence of transstadial transmission from nymph to adult was detected. Larvae from experimentally infected females successfully transmitted virus to clean chicks and virus was recovered from F1 larvae. Venereal transmission was not detected. Virus was present in coxal fluids secreted by infected females after infective meals. This study demonstrates West Nile virus infection in experimentally infected A. arboreus ticks and documents horizontal and vertical transmission in this species.

Azarova, IA; Mishaeva, NP. Protective effect of aminoglycoside group antibiotics in experimental encephalitis of mice, induced by West-Nile virus. Sixth International Conference on Antiviral Research, Venice, Italy, April 25-30, 1993. Antiviral Research. 1993; 20 (SUPPL. 1) 180. ISSN: 0166-3542.

NAL Call No.: QR355.A5

Descriptors: Experimental infections in mice, efficacy of antibiotics, aminoglycoside family of antibiotics.


Baqar, S; Hayes, CG; Murphy, JR; Watts, DM. Vertical transmission of West Nile virus by Culex and Aedes species mosquitoes. American Journal of Tropical Medicine and Hygiene. 1993 Jun; 48(6): 757-62. ISSN: 0002-9637.

NAL Call No.: 448.8 Am326

Descriptors: transmission studies, mosquitoes as disease vector, Aedes albopictus, Aedes aegypti, Culex tritaeniorhynchus, intrathoracic inoculation with live virus, newborn mouse assay, F1 adults, vertical transmission, possible transmission mode in natural systems.

Abstract: Experiments were conducted to determine whether West Nile (WN) virus was transmitted vertically by colonized strains of Aedes albopictus, Ae. aegypti, and Culex tritaeniorhynchus. Female mosquitoes were infected by intrathoracic inoculation with WN virus, and the F1 progeny were tested for virus by the fluorescence antibody technique and the newborn mouse assay. Each of the three mosquito species transmitted WN virus to F1 adults derived from immature forms reared at 26 degrees C. The minimal filial infection rate (MFIR) ranged from 1:124 to 1:138 for Ae. albopictus, from 1:62 to 1:172 for Ae. aegypti, and from 1:325 to 1:859 for Cx. tritaeniorhynchus. The MFIR for Cx. tritaeniorhynchus reared at 20 degrees C was 1:213 for larvae and 1:390 for pupae, and 1:208 for larvae and 1:554 for pupae reared at 26 degrees C. These data are the first reported evidence of vertical transmission of WN virus by mosquitoes, and therefore warrant further studies to determine whether vertical transmission occurs among WN viral-infected mosquitoes in nature.


Cornel, A.J.; P. Jupp; N. Blackburn. Evironmental temperature on the vector competence of Culex univittatus (Diptera: Culicidae) for West Nile virus. Journal of Medical Entomology. Mar 1993. v. 30 (2) p. 449-456. ISSN: 0022-2585.

NAL Call No.:  421 J828

Descriptors: Culex univittatus, mosquitoes, disease vectors, environmental temperature effects, medical entomology, vector competence, West Nile virus, South Africa.

Abstract: The effects of the extrinsic incubation temperature on the vector competence of Culex univittatus Theobald for West Nile (WN) virus were studied. A mean titer of 7.0 log(10) CPD(50)/ml of mosquito suspension was reached in orally infected mosquitoes after 11, 15, and 16 d of incubation at 26 and 30 degrees C and at fluctuating temperatures in an outside cage (mean temperature, 23.5 degrees C), respectively. In contrast, 22 and 58 d were required to reach the same titers at 18 and 14 degrees C, respectively. Transmission rates of 100% were reached after 58 d (14 degrees C), 22 d (18 degrees C), and 15 and 16 d (30 degrees C and outside). Except at 30 degrees C, transmission rates fluctuated; e.g., at 18 degrees C from day 19, the transmission rate was 80-100%, whereas at 14 degrees C on day 36, the transmission rate was 60% and thereafter 20-100%. The maximum transmission rate occurred concurrently with maximum titers of virus secreted into capillary tubes during in vitro transmission attempts. Mosquito longevity increased as incubation temperature decreased and was maximum at 114 d at 14 degrees C. Mosquitoes that were transferred from 14 to 26 degrees C after 49 d subsequently oviposited, engorged on a pigeon, and transmitted virus, which indicated the possibility for overwintering of WN virus in adult Cx. univittatus. Vector competence at outside cycling temperatures was intermediate between that at 26 and 30 degrees C, indicating that incubation at 26 degrees C would give a fair reflection of the vector competence of Cx. univittatus during the summer near Johannesburg. Two human epidemics of WN virus are reevaluated in the light of these results; it is concluded that, in addition to abnormal rainfall, higher than normal temperatures were important factors for their occurrence.


Porter, KR; Summers, PL; Dubois, D; Puri, B; Nelson, W; Henchal, E; Oprandy, JJ; Hayes, CG. Detection of West Nile virus by the polymerase chain reaction and analysis of nucleotide sequence variation. American Journal of Tropical Medicine and Hygiene. 1993 Mar; 48(3): 440-6. ISSN: 0002-9637.

NAL Call No.: 448.8 Am326

Descriptors: PCR based detection assay, 7 WNV isolates, Kunjin, Japanese encephalitis, St. Louis encephalitis, yellow fever, sensitivity levels, homology.

Abstract: A polymerase chain reaction (PCR) assay was developed to rapidly detect and identify West Nile (WN) virus. The RNA from seven isolates of WN virus from six countries and four other flaviviruses (Kunjin, Japanese encephalitis, St. Louis encephalitis, and yellow fever viruses) was reverse-transcribed (RT) and amplified by PCR. The nucleotide sequences of the amplified products were determined by a rapid, automated DNA sequencing method. The WN virus RT/PCR assay detected the target gene segment of sequencing method. The WN virus RT/PCR assay detected the target gene segment of isolates from both the African-Middle Eastern group and the Indian group with a sensitivity of approximately 0.05 pg of viral RNA. Kunjin virus was the only other flavivirus tested that produced a band of the appropriate size. Five of seven WN virus isolates showed 92-98% homology in the nucleotide sequence of their PCR products. The sequence of one isolate was virtually identical to the published sequence of the Nigerian isolate (99.5% homology). No correlation was established between the degree of nucleotide homology, geographic location, time of isolation, or source of the isolates.

Sreenivasan, V; Ng, KL; Ng, ML. Brefeldin A affects West Nile virus replication in Vero cells but not C6/36 cells. Journal of Virological Methods. 1993 Nov; 45(1): 1-17. ISSN: 0166-0934.

NAL Call No.: QR355.J6

Descriptors: virus-host interaction of glycoprotein processing, WNV Vero cells, C6/36 cells, brefeldin A, transport of glycoproteins to Golgi apparatus.

Abstract: A fungal metabolite brefeldin A (BFA) was used to study virus-host interaction in glycoprotein processing in West Nile virus-infected Vero and C6/36 cells. The results indicated that as little as 1 microgram/ml of BFA resulted in complete breakdown in the Golgi organelle in infected Vero cells. This led to modifications of the glycoproteins which could not be efficiently used in infectious virion formation. In contrast, as much as 10 micrograms/ml of BFA in culture medium did not affect either glycoprotein formation or production of infectious particles in C6/36 cells. The results showed that in Vero cells, the transport of glycoproteins to the Golgi apparatus is important in West Nile virus infection. It also showed that BFA could be used as a tool to understand further the trafficking of glycoprotein from the ER to Golgi in flavivirus infection in Vero cells.

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February 26, 2003