Virus Update: Eastern Equine Encephalitis Diagnosed in a Horse in Wisconsin

[VIDEOSINGLE type=”youtube” keyid=”17TlL_BNf3g”, width=”560″, height=”344″]
This video from the University of Maine is a year old, so don’t be confused by the references to “last year”. I think this is one of the best videos available, made at any time, to help horse owners understand the basics of Eastern Equine Encephalitis (EEE)

Eastern equine encephalitis (EEE) has caused the death of two alpacas in Dunn County, Wisconsin and a horse in that state has also been diagnosed with the deadly mosquito-borne virus that attacks the central nervous system. In other states, the watch is on; the virus has been found in mosquitoes in several states, and was diagnosed in the death of one horse in New York and others in the Florida panhandle region, as reported last week on The Jurga Report.

Although humans may also contract EEE, no human cases have appeared in Wisconsin or any other state.

“Horse owners who have not already had their animals vaccinated this year for EEE and other mosquito-borne diseases should take this as a warning, and those who have vaccinated should check with their veterinarians to see whether a booster is indicated,” said Wisconsin State Veterinarian Dr. Robert Ehlenfeldt in a press release today.

They’re everywhere. But are they infected with EEE© (Carol Spear image)

“There is no approved vaccine for alpacas. Alpaca owners should consult their veterinarians about preventive measures,” he said.

According to Ehlenfeldt, blood samples were sent to the University of Minnesota Veterinary Diagnostic Laboratory on July 9. Initial positive results there were confirmed by the Pennsylvania Animal Diagnostic Laboratory System, which reported final positive results today.

EEE may be transmitted by mosquito sting to horses, birds, and humans. It is unusual, but not unheard of, for alpacas and other mammals to be infected. The virus is not transmitted between animals or between animals and humans.

Symptoms in horses include depression, loss of appetite, drooping eyelids and lower lip, aimless wandering and circling, blindness and sometimes paralysis. There is no cure; the disease must run its course and has a mortality rate of 90 percent or higher.

Wisconsin experienced a major outbreak of EEE in 2001, with 69 confirmed or presumptive positive cases, mostly in northwestern Wisconsin. Since then, sporadic cases have occurred. Because EEE follows mosquito populations, it normally occurs beginning in mid- to late summer and remains a threat until the first killing frost.


The Wisconsin advisory states that horses that have never been vaccinated will need two doses of vaccine two to four weeks apart, and the vaccine will take at least two weeks to build up enough antibodies to protect them. A booster would normally be only one dose and would take about four days to be effective. Vaccines will not protect horses that have already been infected when they receive the injections. Vaccines are available that protect against other strains of equine encephalitis along with EEE, and a separate West Nile virus vaccine is also available.

“Northern Wisconsin has good mosquito habitat, and that has been where we’ve seen most cases of EEE over the years,” Ehlenfeldt said. “It’s been a wet summer up north, and mosquito populations are really high. If we get a good long fall, we could see a lot more cases.”

In addition to vaccination, owners can take steps to reduce their animals’ exposure to mosquitoes. They should eliminate standing water by removing objects like old tires or even the folds in tarps where water collects, and frequently changing water in water troughs, bird baths and similar containers. Owners should also keep their animals insides barns if possible from dusk through dawn, when mosquitoes are most active.

Please note that this is the very beginning of the EEE season for 2011. Cautionary measures must be put into place and followed until there is a killing frost in most states. Find solutions that work for you and your horses to beat the mosquitoes before your state is added to the list where infected mosquitoes have been found. And once you find workable solutions, plan to keep them in place for the months ahead. This will be a long season.

To learn more: Please read the AAEP Report on Eastern/Western Equine Encephalitis and check with your veterinarian that all horses on your property or in your care are up-to-date on their vaccinations. Monitor news via The Jurga Report and your state animal health department for updated occurrences of the disease and the presence of infected mosquitoes in your area. Experiment with repellents and protective turnout garb to come up with the safest, most effective solution for each individual horse in your care when and if they are turned out.




Related Posts

Gray horse head in profile on EQ Extra 89 cover
What we’ve learned about PPID
Do right by your retired horse
Tame your horse’s anxiety
COVER EQ_EXTRA-VOL86 Winter Care_fnl_Page_1
Get ready for winter!


"*" indicates required fields


Additional Offers

Additional Offers
This field is for validation purposes and should be left unchanged.