To determine the extent to which clinical outcome and extent and source of virus shedding in VSNJV infected cattle and horses are dependent on virus strain and route of inoculation, and to define the potential for virus transmission by insects and by animal-to-animal contact in relation to livestock infection with epidemic VSNJV strains.
NON-TECHNICAL SUMMARY: Vesicular stomatitis (VS) is extremely important to animal health authorities because the clinical symptoms in cattle, swine, and other cloven-hoofed animals mimic those of foot-and-mouth disease. Recent epidemics of vesicular stomatitis New Jersey virus (VSNJV) have occurred in the United States as recently as 2004. While the 1982-83 epidemic primarily involved cattle, the epidemics in 1995, 1997, and 2004 primarily involved horses. These data, which suggests that individual VSNJV strains have distinct host predilections, are supported by reports of previous unsuccessful attempts to produce VS in cattle by experimental inoculation with swine and equine VSNJV strains, and by a report of decreased virulence of a bovine VSNJV strain in experimentally infected pigs. The goal of our research group is to better elucidate the epidemiology of VSNJV. We will achieve our this by completing the following specific objectives; 1) To determine the extent to which clinical outcome and extent and source of virus shedding in VSNJV infected cattle and horses are dependent on virus strain and route of inoculation, and 2) To define the potential for virus transmission by insects and by animal-to-animal contact in relation to livestock infection with epidemic VSNJV strains. The results of the proposed research will greatly influence our ability to predict, control, and prevent VS epidemics. Additionally, the identification of such phenotypic variation may lead to a much more complete understanding of genetic function and the development of safe and efficacious vaccines.
APPROACH: Initially we will infect cattle with a 1982 Colorado bovine VSNJV strain via four different routes (intradermal inoculation of the snout or muzzle, lip scarification, skin scarification, and orally) with two VSNJV doses to determine the best dose/route combination for infecting cattle. Animals will be examined for lesions and sampled for virus isolation and serology on post-infection days (PID) 1-8, 10, and 12. Additional samples for virus isolation will include nasal cavity swabs, tonsil, nasal exudates, and saliva. Animals will be euthanized on PID 12 then necropsied. Select tissues will be collected for virus isolation and immunohistochemistry. Specific VSNJV neutralizing antibody response will be determined using a microtiter neutralization test. We will use the best dose/route combination as determined in the initial study and infect cattle with the 1995 Colorado equine and Ossabaw Island swine VSNJV strains. In independent trials, horses and pigs will be experimentally infected with the 1982 Colorado bovine VSNJV strain via routes which have consistently produced VS in these animals in previous work (pig snout and horse muzzle and/or tongue) to determine if clinical outcome and extent and source of virus shedding are dependent on the virus strain. Sampling protocol is as stated above. We will use black flies as an insect model to define the potential for virus transmission by insects. Independent trials will be conducted for cattle with each VSNJV strain (1982 Colorado bovine and 1995 Colorado equine) and for horses with the 1982 Colorado bovine VSNJV strain. Black flies will be infected via intrathoracic inoculation to ensure infection status. Infected black flies will be placed into a feeding cage (15 flies per cage). The cage will be held on the muzzle/lip of each experimental animal for 20 min. or until at least 1 black fly feeds. The development of VSNJV neutralizing antibodies in the experimental animals, as determined by microtiter serum neutralization, will be considered as evidence of virus transmission. Progression of clinical disease, if present, will be followed. Sampling protocols will be as described above. We will determine if insects can be infected with bovine and equine VSNJV strains via direct feeding on infected hosts by allowing non-infected black flies to feed from each host immediately following infection, and on PIDs 1, 2, 3, 4, and 5. At each time point, twenty-five caged, non-infected black flies will be allowed to feed on or near the site of original infection on each host. Blood-fed flies will be individually assayed for infectious virus by tissue culture inoculation. We will determine the degree to which bovine and equine VSNJV strains are transmitted via animal-to-animal contact by housing seronegative contact animals together with previously infected animals. Contact animals will monitored daily. Samples from contact animals for virus isolation will taken on post contact days (PCD) 0-7. Blood samples for serology and virus isolation will be taken on PCD 0, 4, 9, and 13. Contact animals will be euthanized on PCD 13.
PROGRESS: 2005/09 TO 2009/09 <BR>
OUTPUTS: Activities: Research was concluded. Analysis of experimental results are complete. Results have been disseminated via presentations at several scientific conferences and will be presented at the 2009 USAHA:AAVLD meeting in San Diego. Services: PI has had numerous conversations regarding VSV epidemics in the western United States. Additionally serum generated from our experimental animals was provided to USDA APHIS NVSL to use in their laboratory performance verification assays. <BR> PARTICIPANTS: Daniel Mead - PD/PI responsible for all aspects of the project. Elizabeth Howerth - co PI assists with animal infections and necropsy. Deb Carter - technician assist with sampling and necropsy Training Paul Smith - graduate student. Additional training - project team trained University of Georgia animal resources personnel on protocols and procedures for working in a BSL-3Ag facility.<BR> TARGET AUDIENCES: Target audience is the agricultural community as well as persons in regulatory agencies such as USDA APHIS. <BR> <BR>
IMPACT: 2005/09 TO 2009/09<BR>
Outcomes: We have demonstrated that VSNJV can be transmitted from an infected animal to a naive animal via mechanical insect transmission. Additionally, we have demonstrated that, in cattle, there are significant differences in clinical response following infection with different epidemic VSNJV viruses. For example, infection of cattle with the 1982-83 virus resulted in severe disease, whereas infection of cattle with the 1995 and 2006 epidemic viruses and with a sand fly isolate from an endemic region on Ossabaw Island, Georgia, resulted in mild disease when disease was present. We did not detect differences in clinical outcome in horses following infection with the same viruses. Additional findings include - transmission of VSNVJ among horses via horse-to-horse contact and transmission of the 1982-83 virus among cattle via cow-to-cow contact. Finally, we demonstrated that VSNJV-infected horses and cattle can serve as a source of the virus for biting flies. Collectively, these results have far reaching implications on understanding VSNJV epidemiology and aid in designing and implementing more effective control methods. Additionally, the results will aid in predicting virus spread during future epidemics.