Vesicular Stomatitis Impacts Livestock Exhibitions

Summer and fall are the times of year when many livestock producers participate in fairs, exhibitions and shows. However, it is not the time to be lax about biosecurity measures given the ongoing risks of commingling animals at these events. Horses and other livestock being hauled to and from exhibitions may contribute to spreading vesicular stomatitis (VS) and other highly contagious diseases. Current and historic VS incidence reports are published by the USDA Animal and Plant Health Inspection Service.

Vesicular stomatitis is the most common vesicular disease of livestock in the United States, Mexico, Central and South America. The causative virus was first isolated in 1925 (Lambert, T., Leedom Larson, K.R., 2016), but signs have been reported since the 1800s. In warmer regions of the Americas, VS is considered an endemic disease of livestock. Although livestock can recover from this disease, it is important to know what the signs are and how to prevent it.

Disease Specifics

Vesicular stomatitis lesion in a horse’s mouth. Source: Center for Food Security and Public Health

The disease is caused by a virus that has two serotypes (separate groups within a species of microorganisms that all share a similar characteristic): the New Jersey and the Indiana serotypes. The New Jersey serotype was responsible for the 2019 outbreak. Both types of VS have been seen sporadically throughout the disease’s history, with the largest outbreak affecting nine states in 2005 (Traub-Dargatz, J., & Pelzel-McCluskey, A., n.d. ). The 2019 U.S. outbreak was nearly as extensive, reaching the seven states mentioned above, and spreading to 1,078 premises as of the USDA September 26, 2019 VS report. The disease is reportable, meaning that when diagnosed it must be reported by a producer, the herd veterinarian or the state veterinarian to the USDA APHIS Veterinary Services.

Primarily a disease of horses, cattle and swine, VS can also be found in sheep, goats, llamas and alpacas. It is seasonal, appearing during the warmer seasons and disappearing during the winter. Blood-sucking insect vectors such as black flies, sand flies and midges transmit the disease to livestock (Traub-Dargatz, J., & Pelzel-McCluskey, A., n.d.). The virus can spread between animals through direct contact with infected animals, or from exposed equipment (fomites) including buckets, feed, trailers or manure. It is considered a zoonotic disease that on rare occasions can infect humans after handling infected animals, resulting in flu-like symptoms.

The incubation period for VS is two to eight days before an animal develops any signs of infection. Clinical signs consist of:

• Blisters.
• Sores on the tongue, mouth lining, nose, lips, coronary bands, udder or sheath.
• Drooling or frothing at the mouth.
• Fever.
• Reluctance to eat.

Biosecurity Measures

In non-equine species these signs appear similar to foot-and-mouth disease, so testing must be done to make the correct diagnosis. Laboratory testing is the best method to confirm VS, by looking for specific antibodies to the virus in a blood sample or by isolating the virus with a swab sample from a lesion. The virus generally runs its course within two weeks. Typically animals will survive the infection; however, it can take up to two months for the lesions to completely heal.

In order to protect livestock, the following biosecurity measures should be followed:

• Call your veterinarian immediately if you see signs of the disease.
• Separate affected animal(s) from all healthy animals on the property.
• Isolate new or returning animals.
• Handle all healthy animals before sick animals.
• After handling sick animals make sure to wash and disinfect your hands and boots; change and wash clothes as well.
• Control biting flies using fly paper or sugar water.
• Keep animals stalled or under a roof at night to reduce exposure to flies.
• Keep living quarters clean to limit flies.
• Feed and water stock from individual buckets.
• Check exhibitions and other events for veterinary inspection certification requirements, restrictions and their biosecurity policies.

Economic Impacts

During a 1982 outbreak in an Idaho dairy herd, 320 cows out of a 500-cow herd contracted the disease. The total cost of this outbreak was about $50,000 to the farm (Leder, R. R., Mass, J., & Evermann, J. F., 1983). Outbreaks impact the livestock exhibitions as well. The 2019 Trapper’s Stampede Rodeo at the Cody Stampede Park in Wyoming was postponed due to fears that the participating horses would be exposed to VS. The Ohio Department of Agriculture designated an import restriction for horses from states with confirmed or suspected cases of VS, potentially affecting entrants to the world’s largest single-breed horse show, the All-American Horse Congress scheduled for October 1, 2019, at the Ohio Expo Center.

Check for Movement Restrictions

VS can quickly compromise the health of agricultural animals and adversely impact local and regional economies. In the event of a disease outbreak like this, take extra precautions for your horses and other livestock by practicing the biosecurity measures discussed here, and monitor for signs regularly. States may impose certain restrictions for horses and livestock coming from VS affected states. Click on this link to the Colorado Department of Agriculture website for an example of state restrictions in place during the 2019 VS outbreak. Check with your state animal health officials or those in the destination state for information about livestock movement restrictions and other requirements.

References

Lambert T, Leedom Larson KR. 2016. Vesicular stomatitis virus. Swine Health Information Center and Center for Food Security and Public Health. Retrieved from http://www.cfsph.iastate.edu/pdf/shic-factsheet-vesicular-stomatitis-virus

Traub-Dargatz, J., & Pelzel-McCluskey, A. (n.d.). Overview of Vesicular Stomatitis. Merck Veterinary Manual. Retrieved from https://www.merckvetmanual.com/horse-owners/disorders-affecting-multiple-body-systems-of-horses/vesicular-stomatitis-in-horses

Leder, R. R., Mass, J., & Evermann, J. F. (1983). Epidemiologic investigation of vesicular stomatitis in a dairy and its economic impact. Bovine Practitioner, 18, 45–49. Retrieved from https://www.cabdirect.org/cabdirect/abstract/19842242274

United States Department of Agriculture, Animal and Plant Health Inspection Service (2019, September). 2019 Vesicular Stomatitis Virus (VSV) Situation Report. Retrieved from https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/cattle-disease-information/vsv-reports

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About the Author
Samantha Shields
Samantha Shields was an undergraduate student at the University of Vermont, studying for a Bachelor of Science in Biological Science, and a minor in Animal Science. She worked with ADBCAP Director Julie M. Smith, DVM, PhD, as an online outreach assistant intern. Samantha assisted with content development for the Healthy Farms Healthy Agriculture website by evaluating, summarizing, and presenting information about protecting animal health. At the University of Vermont, she was an active member of many programs including RALLYTHON, University of Vermont Program Board, Campus Recreation, and the Women’s Club Hockey. Samantha is interested in pursuing the field of epidemiology after graduation. She has a particular interest in the research of different factors that result in diseases, as well as public health emergency planning and response.

About the Editor
Joanna Cummings
Cummings received a bachelor of science degree in horticulture from The Pennsylvania State University, with a specialization in vegetable crop and greenhouse production. At PSU, she was a research technician on no-tillage vegetable crop experiments, and a greenhouse assistant in the All-American Selections Research Gardens. Her career in the agriculture industry includes field research, work with dairy and vegetable farms, and as a greenhouse manager, estate gardener, landscaper and market garden entrepreneur. She transitioned to the science communication field after receiving a master of science degree in environmental communications from Antioch University New England. At Antioch, she was a field botany laboratory teaching assistant and manager of the herbarium.
She works with Associate Research Professor Julie M. Smith as a communications professional in the University of Vermont Animal and Veterinary Sciences Department. She is the webmaster for the Healthy Farms Healthy Agriculture website.

About the Editor
Dr. Julie Smith
Dr. Julie Smith is a research associate professor at the University of Vermont. Julie received her B.S. in Biological Sciences, D.V.M., and Ph.D. in Animal Nutrition at Cornell University. Since 2002, she has applied her veterinary background to programs in the areas of herd health, calf and heifer management, and agricultural emergency management. She has taught Animal Welfare, Calf Biology and Management, and ABCs of Biosecurity to undergraduates, mostly in the Department of Animal and Veterinary Sciences. 
As a veterinarian and spouse of a dairy farmer, Julie is well aware of the animal health and well-being concerns of dairy animals. Julie has conducted trainings for Extension educators, livestock producers, and community members on the risks posed by a range of animal diseases, whether they already exist in the United States, exist outside of the United States, or pose a risk to both animal and human health. In all cases, she emphasizes the importance of awareness and prevention. In addition, she has led a number of projects on biosecurity and emergency disease preparedness.