The summer of 2014 was a rough one for many horses and their owners in Colorado and Texas. A large-scale vesicular stomatitis (VS) outbreak disrupted normal comings and goings, causing extended quarantines and transportation headaches. In the meantime, thousands of horse owners adopted strict biosecurity strategies to prevent disease spread.
This viral disease can affect many livestock species, but it most often shows up in horses and cattle in the southwestern United States. The virus causes vesicles (blisters) to form primarily on the tongue and lips, around the mouth or nose, on the udder or sheath, or along the coronary bands. These virus-containing vesicles later rupture and become lesions. Biting flies, such as black and sand flies, and biting midges are responsible for spreading the virus, although animals can become infected though direct contact with lesions or contaminated objects/areas. People can sometimes contract the disease from handling infected animals with open lesions.
Vesicular stomatitis is currently “reportable,” which means treating veterinarians are required to contact state and federal regulatory animal health officials for additional investigation and diagnostic testing when they see a suspected case. If officials confirm the case is VS, disease management includes quarantining all susceptible animals on the premises, isolating and providing supportive care to affected animals, and deploying mitigation strategies to control biting fly vectors and prevent additional cases. The quarantine on VS-positive premises remains in effect until 21 days after all animals’ lesions have healed. While horses with mild lesions usually heal well on their own, horses with severe lesions or older horses sometimes require hospitalization and intravenous fluid administration, particularly if they are too uncomfortable to eat or drink. It can be challenging to carry out effective vector control strategies, especially when it may be necessary to spray each horse daily with insecticide or when horses are kept on pasture with constant vector exposure. Finally, moving horses interstate from nonaffected premises can be difficult, as many other states implement enhanced movement restrictions and requirements for horses coming from a state experiencing an outbreak.