Although they've increased since last update, the number of confirmed equine West Nile virus (WNV) and Eastern equine encephalitis (EEE) cases has steadied, according to the Animal and Plant Health Inspection Service (APHIS) disease maps.
At the most recent update (Nov. 20), APHIS reported 609 equine WNV cases nationwide and 206 cases of equine EEE since the beginning of the year; both numbers increased from the previous update (Oct. 30), which reported 566 WNV cases and 195 EEE cases. Both current totals far exceed the number of WNV and EEE cases reported nationwide in 2011 (87 and 60, respectively).
As of Nov. 20, Texas had reported the most WNV cases (109), followed by Louisiana (62), Pennsylvania (47), Oklahoma (42), Mississippi (37), Iowa (35), and Indiana (30). Last year, California had the nation's highest WNV total when they reported 15 cases, according to APHIS. The only states in the continental United States that have not reported at least one equine WNV case this year are Delaware, Kansas, Maine, New Hampshire, Vermont, and West Virginia, according to APHIS.
Also as of Nov. 20, Louisiana reported the most equine EEE cases (55), followed by Florida (33), Mississippi (31), and North Carolina (20), according to APHIS. Last year, Wisconsin and New York reported the most cases with 31 and 10, respectively.
Alaska and Hawaii have never reported an equine case of either WNV or EEE.
Another mosquito-borne disease, Western equine encephalitis, has not been identified in the United States this year.
Although mosquito populations are likely diminishing in the colder climates, owners in warmer climates should continue to protect their horses against these potentially deadly diseases.
Vaccinating horses against WNV and EEE coupled with mosquito control are the most important ways to minimize an animal's chances of becoming infected. In the northern regions of the United States, most veterinarians recommend vaccinating horses in the spring prior to peak mosquito levels. In the south, where mosquito populations are present year-round, veterinarians might recommend more frequent vaccination.
Minimizing mosquito populations near your horses by eliminating mosquito breeding and resting areas will make it more difficult for the insects to bite and infect horses and the people who care for them.
For example, reduce or eliminate sources of stagnant or standing water, remove muck from areas near the horses, stable horses during peak mosquito periods (i.e., dawn and dusk), use equine-approved mosquito repellants, place fans inside barns or stalls to maintain air movement, keep weeds and grass trimmed, and avoid using incandescent bulbs inside stables at night. Instead, place incandescent bulbs away from the stables to attract mosquitoes to areas away from horses.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.