Officials with the Michigan Department of Agriculture and Rural Development (MDARD) and Michigan State University (MSU) Diagnostic Center for Population and Animal Health (DCPAH) confirmed the first West Nile case of the year in an unvaccinated Montcalm County horse due to West Nile Virus (WNV) infection. The five-year-old Standard bred gelding developed sudden incoordination in the hind limbs and is currently undergoing treatment (supportive care) for West Nile Virus.
“WNV is spread from wild birds to humans, horses, and in some cases pets, through infected mosquitoes and causes encephalitis, or inflammation of the brain,” said State Veterinarian Dr. Steven Halstead. “Signs of WNV may include stumbling, limb weakness, facial paralysis, difficulty urinating and defecating, fever, blindness, seizures, and struggling to get up. There is no specific treatment for WNV encephalitis, but supportive care can help horses survive until their natural defenses eliminate the virus.”
MDARD partners with MSU’s DCPAH for diagnostic testing whenever clinical signs indicate the animal could be suffering from a reportable disease, Dr. Halstead said.
“Our commitment to diagnostic testing for new and emerging zoonotic diseases such as West Nile Virus strengthens partnerships with state agencies including MDARD, Department of Community Health, and Department of Natural Resources, as well as national agencies like the Centers for Disease Control and Prevention,” said Dr. Carole Bolin, MSU, DCPAH Director. “We conduct approximately 100 tests for WNV annually.”
“Licensed West Nile Virus vaccines for horses are available and owners are encouraged to vaccinate yearly, in consultation with private veterinary practitioners,” said Dr. Halstead. “Horse owners should take measures to reduce the risk of mosquito exposure to themselves and their horses.”
The mosquitoes most likely to transmit WNV to humans lay eggs in small pools of standing water. Adult mosquitoes can hatch in 10 days in the warmest months of the summer. Mosquitoes become infected and transmit WNV after feeding on birds carrying the virus. Within 10 to 14 days, the mosquito can transmit the virus to humans and horses.
Since West Nile Virus is spread to horses through the bite of an infected mosquito, protection measures that reduce the exposure to mosquito bites should be adopted. Horse owners should follow these tips to prevent mosquito-borne illness:
1. Vaccinate. Inexpensive vaccines for WNV are readily available. It is not too late to vaccinate horses this season. Talk to your veterinarian for details.
2. Use approved insect repellants to protect horses.
3. If possible, put horses in stables, stalls, or barns, preferably under fans, during the prime mosquito exposure hours of dusk and dawn.
4. Eliminate standing water, and drain troughs and buckets at least once a week.
For more information about WNV in horses visit www.michigan.gov/emergingdiseases, or DCPAH’s WNV diagnostics is available at www.animalhealth.msu.edu. To be the first to know about an animal disease that may affect livestock or pets in Michigan join the Animal Health Listserv at www.michigan.gov/emergingdiseases.