On September 11, 2006, FADDL confirmed VS in five cattle on a cow-calf premises in Converse county, Wyoming. This was the first case of VS in cattle in Converse county in 2006. Five clinically affected cattle were positive for antibodies to VS New Jersey (VS-NJ) virus on the competitive enzyme-linked immunosorbent assay (cELISA), virus neutralization, and complement fixation tests.
On August 17, 2006, the National Veterinary Services Laboratories (NVSL) in Ames, Iowa confirmed VS in a 10-year-old horse on a premises in Natrona county, Wyoming. This was the first confirmed case of VS in the United States in 2006. The clinically ill horse was positive for antibodies to VS-NJ virus on the cELISA and was also positive on virus isolation for VS-NJ virus. The VS compatible clinical signs and presence of VS-NJ virus meet the definition to classify this horse as the index case for the nation in 2006. There are an additional 29 clinically normal horses and 25 clinically normal cattle also on the premises.
Samples from the virus isolate obtained from the index case were provided by the NVSL to Department of Homeland Security (DHS) and Agricultural Research Services (ARS) scientists on Plum Island. The DHS and ARS scientists were able to sequence and conduct a phylogenetic analysis of the virus showing a close relationship to that of VS virus isolates from the 2005 outbreak in the western United States. Specifically this year's isolate is closely related to viruses isolated from animals in MT and WY in 2005. Therefore, they conclude that this was likely an overwintering of the 2005 VS virus in that region.
Prior to the positive case identified in August 2006, the last case of vesicular stomatitis in the United States was confirmed in Colorado in December 2005.