Contact: Donna Gilson 608-224-5130
donna.gilson@wisconsin.gov
MADISON – Two alpacas have died in Dunn County and a horse has been sickened by Eastern equine encephalitis, or EEE, a mosquito-borne illness caused by a virus that attacks the central nervous system.
Although humans may also contract EEE, no human cases have appeared in Wisconsin.
“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 State Veterinarian Dr. Robert Ehlenfeldt. There is no approved vaccine for alpacas. Alpaca owners should consult their veterinarians about preventive measures, he said.
Blood samples were sent to the University of Minnesota Veterinary Diagnostic Laboratory 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 bite 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.
Horses that have never been vaccinated will need two doses 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.
