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United States Department of Agriculture

Agricultural Research Service

2010 Annual Report

1a.Objectives (from AD-416)
1: Assess the role of insect vector transmission on the pathogenesis of VSV and generate scientific information to understand the epidemiology and trade significance of VSV infection.

1b.Approach (from AD-416)
The assessment of the role of insect vector transmission will be accomplished by; a.) Examining the transmission of Vesicular Stomatitis Virus New Jersey (VSVNJ) to cattle by infected S. vittatum (black fly) bite. b.) Examining the effect of salivary gland extracts on VSV infection in cattle. c.) Evaluating cattle as amplifying hosts for VSV transmission by black flies.

3.Progress Report
Continued research on the pathogenesis of vesicular stomatitis virus in cattle, focusing on insect-transmitted infection and early events in viral infection and host responses. Due to the small size of this project, most of the research activities were done through two collaborative agreements with the University of Georgia-Athens (UGA); one focusing on insect transmission of VSV in cattle and another focusing on pathogenesis of infection. In addition data analysis of VSV epidemiological studies were continued through collaboration with the University of California-Davis Center for Animal Disease Modeling and Surveillance. These analyses determined that specific VSV genetic lineages are capable of overwintering in the Western United States for up to 3 years. This was the first demonstration of overwintering in the US. Additionally a study in endemic areas of Mexico showed that seroconversion of cattle occurs during periods of high insect activity. This helps understand epidemiology of the disease. This work resulted in the manuscript: “Time To Seroconversion To Vesicular Stomatitis New Jersey Virus 1 In Sentinel Cattle In 2 Southern Mexico”; and “Space-Time Analysis And Herd Reproductive Ratio Of Vesicular Stomatitis In Mexico In 2008” both accepted for publication in the American Journal Of Veterinary Research in 2010. An insect transmission study initiated in 2009 at PIADC and continued at UGA demonstrated the VSV could be horizontally transmitted between black flies while co-feeding on non-infected cattle. This route of transmission of an arthropod-borne virus between insects contrasts conventional routes where insects obtain the virus through a blood meal from viremic host. It was also shown that subclinically infected cattle can serve as amplifying hosts for VSV transmission between infected and non-infected back flies. We also demonstrated that clinically infected cattle can serve as sources of virus to back flies. A manuscript was submitted detailing this research: Smith PF, et al, Domestic Cattle (Bos taurus) as a nonconventional amplifying host of Vesicular Stomatitis New Jersey Virus (Rhabdoviridae: Vesiculovirus), submitted to Medical and Veterinary Entomology. The host response to insect-transmitted viral infection was analyzed using immunohistochemistry to detect viral infection. A manuscript was written and accepted for publication describing the early events in viral infection. We determined that the virus replicates most extensively in the stratum spinosum cells of the coronary bands, disseminates to the draining lymph nodes, and undergoes very limited replication at that site, but does not progress any further. Infection via fly bite requires a much lower dose of inoculum and lesions develop more extensively than in needle infections. The results suggest that there are factors provided by the insect that potentiate viral infection.

1. Described the early stages of Vesicular Stomatitis Virus (VSV) infection in cattle after infection by fly bite or scarification. In this series of experiments, we characterized the viral replication process and the influence of fly bites on the developmet of lesions after VSV infection in cattle. We documented, for the first time, the early phases of VSV infection comparing fly bite infection (FB) with direct virus inoculaiton by scarification (SC). The infection started at the inoculation site and later expanded to the draining lymph nodes for by SC and FB inoculated animals. Interestingly, both inoculation methods showed similar virus distribution, but the FB infection required 1,000-10,000 times smaller does than SC to cause similar disease. These results suggest that there may be factors facilitating infection induced by fly bite. These results are relevant to understanding why insect transmission of VSV is so effective and may help in implementing disease control methods.

2. Demonstrated that cattle can serve as amplifying hosts for Vesicular Stomatitis Virus New Jersey Virus (VSNJV). In this series of studies we demonstrated transmission from VSNJV-infected black flies to naive black flies while co-feeding on non-infected cattle. We also showed that black flies can infect cattle resulting in clinical disease and that naïve black flies feeding in cattle lesions can become infected. Together these findings demonstrate that cattle can be amplifying hosts during VSV epidemics. These findings are significant since the little is known regarding VSNJV transmission and infection (pathogenesis) in cattle. Our results represent the first report of clinical VS occurring in cattle following the bite of a VSNJV-infected black fly.

Review Publications
Perez, A.M., Pauszek, S.J., Jimenez, D., Kelley, W.N., Whedbee, Z., Rodriguez, L.L. 2010. Spatial and phylogenetic analysis of vesicular stomatitus virus overwintering in the United States. Preventive Veterinary Medicine. 93(4):258-264.

Trujilo, C.M., Rodriguez, L.L., Rodas, J.D., Arboleda, J.J. 2010. Experimental infection of Didelphis marsupialis with Vesicular Stomatitis New Jersey Virus. Journal of Wildlife Diseases. 46(1):209-217.

Last Modified: 11/30/2015
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