The USDA National Veterinary Services Laboratory has confirmed two cases of Vesicular Stomatitis Virus (VSV) in Cochise County, Arizona. The virus was detected in samples from two horses on separate premises, marking the first VSV index cases for the United States in 2025. The last outbreak occurred between May 2023 and January 2024, affecting 319 premises across California, Nevada, and Texas. Arizona’s last confirmed case was on June 24, 2020.
The virus circulates annually between livestock and insect vectors in southern Mexico, occasionally reaching the U.S. when conditions favor the northward movement of infected insects. Known vectors include black flies, sand flies, and biting midges. Initial investigations suggest that infected insect vectors are likely responsible for the recent infections in Cochise County.
The affected premises are under state quarantine until 14 days after lesions appear on the last affected animal. Livestock producers are urged to report any animals showing symptoms such as oral ulcerations or lesions to diseasereporting@azda.gov for examination and sampling. These symptoms can resemble Foot and Mouth Disease (FMD), necessitating thorough investigation.
Interstate movement of Arizona livestock may face restrictions due to VSV detection. Producers must coordinate with accredited veterinarians as Interstate Certificates of Veterinary Inspection (ICVIs) may have altered validity periods. Veterinarians should contact destination states for specific import restrictions and supplementary ICVI statements.
Preventive measures include fly control through cleanliness, manure management, limiting animal turnout during peak fly activity, and using insecticides and repellents. VSV is highly infectious among animals with an incubation period of 3-9 days. Transmission can occur through direct contact with infected fluids or contaminated objects.
Human cases are rare but can result in flu-like symptoms lasting about a week. Handlers should wear gloves and practice good hygiene when dealing with infected animals.
For more information about the disease’s spread patterns, visit this link: https://www.cdc.gov/vsv/index.html
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