2013 Annual Report
1a.Objectives (from AD-416):
1. Elucidate the virus-vector-host interactions responsible for virulence and transmission.
1.1. Determine the tissue tropism in natural hosts after insect transmission and the events mediating viral infection, early pathogenesis, and transmission
1.2. Characterize the mechanisms of insect-to-insect transmission while co-feeding in cattle and assess the role of cattle as amplifying hosts for VSV.
1.3. Test the potentiation of VSV infection by S. vittatum salivary factors.
1.4. Testing virulence and transmissibility of VSV strains making incursions into northern Mexico (and/or southwestern US).
2. Ascertain the viral ecology of disease and factors mediating the re-emergence of VSV in the US.
Genetically characterize the viral strains circulating in endemic areas of Mexico and the epidemiological and ecological factors associated with the emergence and maintenance of specific viral genetic lineages in endemic versus non-endemic settings.
1b.Approach (from AD-416):
1. To examine the virus-vector-host interactions responsible for virulence and transmission, studies will be conducted to determine tissue tropism in cattle after viral infection through insect bite, and the events mediating viral infection, early pathogenesis and transmission. The mechanisms of insect-to-insect transmission while co-feeding in cattle will be characterized and the role of cattle of amplifying hosts for VSV will be assessed. Tests will be conducted to determine the level of potentiation of VSV infection by black fly (Simulium Vittatum) salivary gland factors. Studies will be conducted on the virulence and transmissibility of VSV strains making incursions into northern Mexico.
2. Viral strains circulating in endemic areas of Mexico will be genetically characterized, and the epidemiological and ecological factors associated with emergence and maintenance of the specific viral genetic lineages in endemic settings will be analyzed in comparison to non-endemic virus strains.
Work focused on the understanding of viral ecology and the origin of outbreaks in the United States. The 2012 outbreak in New Mexico continued through July and August 2012. We obtained a large number of field samples from this outbreak through the office of the State Veterinarian of New Mexico as well as from collaboration with USDA, APHIS veterinary services veterinarians in the areas affected by the outbreak. After the collection of samples were sent to Ames, Iowa for laboratory diagnosis, additional samples were collected in RNA-Later, in order to preserve the viral RNA, and were sent to ARS, PIADC for research purposes. A large number of samples yielded positive PCR results and sequences were obtained from most of them. These sequences were compared with a large number of viral strains collected between 2005 and 2011 in Mexico. We confirmed that the 2012 New Mexico outbreak strain originated form a genetic lineage first detected in Southern Mexico in 2006. We documented the migration of this lineage causing outbreaks in Mexico peaking in 2009. We also detected a second genetic lineage in Mexico belonging to viral clade 2 that originated in Guatemala or Belize. This shows a clear pattern of northward migration. This is the first report of a clade 2 virus in Mexico and represents a clear incursion from endemic areas in Central America. It is possible that this virus will migrate northward into to United States in the next 4 to 5 years.
Outbreaks if vesicular stomatitis occur in the southwestern US evey 8-10 years. Previous studies suggested that causative strains originate in endemic areas of Mexico. Using phylogeneticanalysis and time-space relationships of 181 isolates of vesicular stomatitis New Jersey virus (VSNJV) causing disease in Mexico (2005-2011) and the United States (2012) ARS researchers at Greenport, New York documented, for the first time, the emergence of a genetic lineage in southern Mexico causing outbreaks in central Mexico spreading into northern Mexico and eventually into the US in 2012. Additionally, 58 isolates were identified from Mexico that grouped with northern Central America viruses. This study provides the first direct evidence for the emergence and northward migration of a specific VSNJV genetic lineage from endemic areas in Mexico causing VS outbreaks in the US.
Pauszek, S.J., Rodriguez, L.L. 2012. Full length genome analysis of Vesicular Stomatitis New Jersey Virus strains representing the phylogenetic and geographic diversity of the virus. Archives of Virology. 151(1-2):37-48.
Rodriguez, L.L., Pauszek, S.J. 2012. Genus vesiculoviruses. In: Dietzgen R.G., Kuzmin I.V., editors. Rhabdoviruses. Norfolk, UK: Calister Academic Press. p. 23-35.