Confirmed Case(s) – Official Quarantine
Number Confirmed: 2
Number Exposed: 60
Facility Type: Private Facility
Comments: On October 31, 2025, the National Veterinary Services Laboratories in Ames, Iowa, confirmed findings of vesicular stomatitis New Jersey virus (VSNJV) in horses on two separate premises in Cochise County, Arizona. One (1) horse, a 21-year-old grade mare, on the first premises met confirmed vesicular stomatitis virus (VSV) index case definition with compatible clinical signs and viral genome sequence data indicative of VSNJV on swabs from oral lesions. There are an additional 52 horses and 120 cattle on the first premises which are not clinically affected. On a second premises in Cochise County, Arizona, one (1) horse, an 8-year-old Quarter Horse gelding, met confirmed VSV index case definition with compatible clinical signs and viral genome sequence data indicative of VSVNJ on swabs from oral lesions. There are an additional 6 horses and 60 cattle on the second premises which are not clinically affected. These two premises are the 2025 VSV index cases for the United States.
The last outbreak of VSV in the U.S. occurred from May 2023 through January 2024 with a total of 319 premises affected in 3 states (California, Nevada, and Texas). Vesicular stomatitis virus circulates annually between livestock and insect vectors in southern Mexico and only occasionally results in incursion to the U.S. when climatic and ecological factors support movement of VSV-infected insect vectors northward.
Known competent vectors for transmission of VSV include black flies, sand flies, and biting midges (Culicoides spp.). The initial epidemiological investigations on both VSVconfirmed positive premises in Cochise County, Arizona, indicate that incursion of VSVinfected insect vectors is the likely source of infection on these premises. There have been no recent livestock movements on or off either premises. Biosecurity measures and vector mitigation on the affected premises have been instituted to reduce within-herd spread of the virus. The susceptible livestock species are being monitored and both VSV-positive premises will remain under state quarantine until 14 days from the onset of lesions in the last affected animal on the premises.
For more information, go to https://www.aphis.usda.gov/livestock-poultry-disease/cattle/vesicular-stomatitis
See past published Outbreak Alerts: www.coloradohorsesource.com/category/news/alerts
Updates on current disease outbreaks are listed on our EDCC website as they occur and will include the date listed, disease name, location and current status. Specific premises will not be named but the general location by town, county and state will be listed. When locations, events or horses are at risk they will be listed. Updates will be posted as they are received. All information is sourced from: http://equinediseasecc.org/alerts/outbreaks