Animal Industry Services of the Oklahoma Department of Agriculture, Food, and Forestry is encouraging horse owners to take precautions and vaccinate their animals to protect against the West Nile Virus and Eastern Equine Encephalitis.
In years past, Oklahoma averaged approximately 40 cases per year of positive diagnoses of mosquito-carried diseases in horses.
The bird population serves as the reservoir for the viruses, and mosquitoes then transmit the virus to horses and humans. Mosquitoes most likely to transmit WNV and EEE lay their eggs in small pools of standing water. Once the adult mosquitoes hatch, they can become infected with both WNV and EEE after feeding on an infected host, such as a bird carrying the virus. Within 10 to 14 days, the mosquito can transmit the virus to both humans and horses.
“Signs of West Nile Virus include weakness, fever, incoordination, seizures, blindness and difficulty getting up,” said Assistant State Veterinarian Michael Herrin, D.V.M. “There are several vaccines available, and we are encouraging horse owners to visit their veterinarians and determine the vaccination protocol that will best fit their operations.”
Oklahomans can reduce the risk of both EEE and WNV by eliminating standing water which serves as a breeding area for mosquitoes. Horse owners are encouraged to not let water stagnate in birdbaths or water tanks, and keep unused equipment that can collect water, such as a wheelbarrow, turned over when not in use. Water troughs should be emptied and flushed twice a week to remove potential mosquito eggs. When possible, owners should reduce horses’ outdoor exposure at dawn and dusk, the times of day when mosquitoes carrying the viruses are most active.
In addition, ODAFF recommends vaccinating horses against tetanus, equine herpes virus, equine influenza, and rabies.
Tetanus causes progressive paralysis and often death and is transmitted from spores in the ground via lacerations and puncture wounds.
Equine Herpes Virus may cause respiratory symptoms and abortions, but the worst manifestation of the disease is a neurological form that can mimic West Nile Virus. Symptoms of EHV are fever, nasal discharge, incoordination, hind limb weakness, urine dribbling, and a flaccid tail.
Equine Influenza may cause serious upper respiratory tract infection in horses. Fever, nasal discharge and coughing are the primary signs and can cause the performance of a horse to be hindered for weeks to months.
Rabies is a viral disease of warm blooded animals. The main carriers of it in Oklahoma are skunks. They transmit the disease to horses via bites. We see a number of horses each year with Rabies, and horses never recover from the disease. We also see a number of humans who have to take the expensive, uncomfortable vaccinations because of exposure to a rabid horse.
Equine vaccines are available as individual vaccines or in combination. Horse owners should always work with their veterinarian to determine the best product to use for their horses depending on the way the horse is used and housed. A common combination vaccine provides protection against West Nile, Eastern and Western Equine Encephalomyelitis, Tetanus, Influenza, and two strains of EHV. Rabies vaccine is typically an individual vaccine.
ODAFF recommends horse owners and event managers remain at a heightened level of awareness, implement biosecurity practices to minimize potential exposure, consult with a veterinarian on an appropriate vaccination schedule, and report any suspicious illness or neurologic disease.
