Mosquito season will begin soon in Virginia and has already begun in some areas. That means it’s time to start thinking about vaccinating your horses against mosquito-borne illnesses such as West Nile Virus (WNV) and Eastern Equine Encephalitis (EEE). Rabies is not a mosquito-borne disease, but it’s a fatal disease that also requires an annual vaccination.
The Virginia Department of Agriculture and Consumer Services (VDACS) urges all horse owners to check with their veterinarians for vaccination recommendations for their animals. Virginia only had one confirmed case of WNV (Augusta County) and one of EEE (Suffolk) in 2014, although many other states had a much higher incidence of cases.
“Timely vaccination has been shown to decrease WNV and EEE disease incidence drastically,” said Dr. Richard Wilkes, State Veterinarian at VDACS. “Without vaccination, we would expect to see many more infected horses, so we still urge horse owners to consider EEE and WNV vaccination. We believe that in most cases, private veterinarians will recommend them for their clients.”
Vaccines are effective for six to twelve months, so horses should be re-vaccinated at least annually. In areas where the disease occurs frequently, most veterinarians recommend vaccination every six months. For the vaccine to be effective it must be handled and administered properly and be given at least two weeks before the horse is exposed to the virus. Additionally, to stimulate full immunity, horses must be vaccinated twice, about 30 days apart, the first year they are vaccinated. Other prevention methods include destroying standing water breeding sites for mosquitoes, using insect repellents and removing animals from mosquito-infested areas during peak biting times, usually dusk to dawn.
Dr. Wilkes also suggests that owners check about rabies vaccinations for their horses. There were no cases of rabies in Virginia horses last year but four each in 2012 and 2013.
Rabies vaccines are also very effective and vaccinating horses annually can prevent rabies in both horses and humans. In addition to taking measures to decrease the likelihood that horses will be exposed to rabies, routine rabies vaccination is a very important aspect of disease prevention.
All three of these diseases – EEE, WNV and rabies – cause neurologic signs in horses, such as staggering, circling, depression, loss of appetite and sometimes fever and blindness. The diseases can kill anywhere from 30 percent (WNV) to 90 percent (EEE) to 100 percent (rabies) of the horses infected. There is no proven cure for these diseases, but veterinarians can provide supportive therapy to treat symptoms of EEE and WNV and keep horses from injuring themselves. Rabies is always fatal. Humans can become infected with rabies by handling a rabid horse but cannot become infected with EEE or WNV by handling an infected horse, nor can a horse acquire the virus from another infected horse. The presence of an infected horse in the area indicates that mosquitoes carrying EEE or WNV are present, however, and those insects pose a threat to both humans and horses.
For more information on WNV or EEE, contact the Office of Veterinary Services, Division of Animal Industry Services, VDACS, at 804.786.2483 or see vdacs.virginia.gov/animals/diseases.shtml. Information about rabies and rabies exposures can be found on the Virginia Department of Health’s Rabies Control page at vdh.virginia.gov/Epidemiology/DEE/Rabies/. Horse owners should contact their veterinarians for further advice on prevention, diagnosis and treatment.