Location: Foreign Animal Disease Research2008 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
In FY 2008 we continued to focus on the understanding of the pathogenesis of Vesicular Stomatitis Virus (VSV) in cattle after infection by infected black fly bite and contrasting this with infection by scarification. A number of experiments were carried out in cattle that allowed characterization of the infection after fly-bite, reproducing for the first time, clinical disease in cattle by this inoculation method. We showed that virus distribution in insect-bite infected cattle was similar to that observed by scarification of the coronary band; with local viral replication at the inoculation site and the primary lymph nodes draining those sites. In contrast, feeding of infected flies in the neck or flank skin did not result in clinical disease or infection. Interestingly, transmission was observed between flies while co-feeding at these sites. Additional work characterizing the cytokine response after scarification and fly-bite infection is being carried out and will continue in FY 2009. The hypothesis being tested is that insect saliva down-regulates innate responses in the host and potentiates viral growth enhancing infection outcome in cattle. Further studies will continue utilizing salivary gland extracts in FY 2009. This project addresses component 1: Biodefense Research, Problem Statement 1A: Foreign Animal Diseases of the National Program 103 Animal Health.
1. Demonstrated Experimental Transmission Of Vesicular Stomatitis New Jersey Virus From Black Flies (Simulium vittatum) To Cattle The natural transmission of Vesicular Stomatitis Virus (VSV) during epidemics in cattle, the most affected species, remains poorly understood. This study reports the first successful transmission of Vesicular Stomatitis New Jersey Virusl (VSNJV) to cattle by insect bite resulting in clinical disease. Infection resulted in local viral replication, vesicular lesions and high neutralizing antibody titers (>1:256) when infected black flies were allowed to feed at sites where VS lesions are characteristically observed (mouth, nostrils, and foot coronary band). Interestingly, when flies were allowed to feed on flank or neck skin, only limited viral replication occurred, lesions were not observed and low levels of neutralizing antibodies (range 1:8 - 1:32) were detected. Clinical disease induced by infected S. vittatum feeding on the coronary band or the muzzle was similar to that observed after experimental scarification despite the fact that insects presumably delivered a significantly lower viral dose. Viremia was never observed in any of the animals and virus was not recovered from non-affected tissues upon necropsy between 8 and 27 days post-infection. Demonstration that black flies can transmit VSNJV to cattle and that clinical outcome is determined by fly bite site provides a better understanding of vesicular stomatitis epidemiology and its potential prevention and control methods. The progress of this project relates to component 1: Biodefense Research, Problem Statement 1A: Foreign Animal Diseases of the National Program in Animal Health, within the NP 103 Action Plan.
5. Significant Activities that Support Special Target Populations
Nothing to report.
Pauszek, S.J., Allende, R., Rodriguez, L.L. 2008. Characterization of the Full-Length Genomic Sequence of Vesicular Stomatitis Cocal and Alagoas Viruses. Archives of Virology. 153:1353-1357.