Michigan had a very wet spring, combined with high temperatures, it has produced a large crop of mosquitos. Horse owners, according to State Veterinarian Dr. Steven Halstead, are encouraged to vaccinate against mosquito-borne illnesses and prevent mosquito exposure to themselves and horses during warm weather months. Eastern Equine Encephalitis is suspected of being the cause of 129 out of 133 horse deaths in 2010, 56 of the deaths were laboratory confirmed; and West Nile Virus, another mosquito-borne illness has been found in Michigan in past years. Both can affect humans, birds, deer and horses.
"The viruses circulate in mosquito and bird populations throughout the spring and early summer, and gradually spill over to horses, and potentially to humans," saysHalstead. "Owners should plan to vaccinate horses now to protect them against these diseases. Michigan typically sees an increase in the number of cases of EEE and WNV in late summer and early fall each year."
EEE, commonly called sleeping sickness, and WNV are both caused by specific viruses found in wild birds. Mosquitoes that feed on birds carrying EEE or WNV can transmit the disease to horses and humans. Some birds are able to harbor the viruses without becoming acutely ill, thereby serving as reservoirs for the diseases.
Clinical signs of both viruses in horses include: depression, fever, muzzle weakness, the horse is often down and unable to get up, sweating, dehydration, seizing, grimacing, not feeding, head down, stumbling, blindness and circling.
"We encourage diagnostic testing because EEE and WNV can look like rabies and while rabies is not very common in horses, rabies is contagious from infected horses to people," Halstead says. "Horses do not develop high enough levels of EEE or WNV in their blood to be contagious to other animals or humans; however, vaccinations against EEE, WNV and rabies are always critical to protect horse health."
Horse owners should follow these tips to prevent mosquito-borne illness:
• Vaccinate your horses. Inexpensive vaccines for EEE and WNV are readily available and should be repeated at least annually. It is never too late to vaccinate horses. Talk to your veterinarian for details.
• Use approved insect repellants to protect horses.
• If possible, put horses in stables, stalls, or barns during the prime mosquito exposure hours of dusk and dawn.
• Eliminate standing water, and drain troughs and buckets at least two times a week.
For more information about WNV or EEE in horses, contact MDARD's Animal Industry Division at 517-373-1077 or visit www.michigan.gov/mda.MDARD encourages horse owners to report suspect cases to the department at 517-373-1077 or, after hours, at 1-800-292-3939. When disease surveillance begins, weekly updates of affected animals will be posted on the Emerging Diseases website at www.michigan.gov/emergingdisease.