Year’s first West Nile virus case found in Montcalm County horse

By Daily News • Last Updated 2:19 pm on Wednesday, August 15, 2012

LANSING — State officials confirmed the first West Nile case of the year in an unvaccinated Montcalm County horse due to West Nile virus infection. The five-year-old standardbred gelding developed sudden incoordination in the hind limbs and is currently undergoing treatment (supportive care) for West Nile virus.

“West Nile virus 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 West Nile virus may include stumbling, limb weakness, facial paralysis, difficulty urinating and defecating, feverWest Nile virus 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.”

Michigan Department of Agriculture and Rural Development (MDARD) partners with Michigan State’s Michigan State University Diagnostic Center for Population and Animal Health (DCPAH) for diagnostic testing whenever clinical signs indicate the animal could be suffering from a reportable disease, Dr. Halstead said.

“Licensed West Nile virus vaccines for horses are available and owners are encouraged to vaccinate yearly, in consultation with private veterinary practitioners,” Dr. Halstead said. “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.

“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,” DCPAH Director Dr. Carole Bolin said. “We conduct approximately 100 tests for West Nile virus annually.”

Because 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:

• Vaccinate. Inexpensive vaccines for WNV are readily available. It is not too late to vaccinate horses this season. Talk to your veterinarian for details.

• Use approved insect repellants to protect horses.

• If possible, put horses in stables, stalls, or barns, preferably under fans, during the prime mosquito exposure hours of dusk and dawn.

• Eliminate standing water, and drain troughs and buckets at least once a week.

For more information about West Nile virus in horses visit, or DCPAH’s West Nile virus diagnostics is available at To be the first to know about an animal disease that may affect livestock or pets in Michigan join the Animal Health Listserv at

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