Equine WNV, EEE Case Totals Continue to Rise

Although cooler temperatures have arrived in many parts of the country, the number of equine West Nile virus (WNV) and Eastern equine encephalitis (EEE) cases still continues to rise.

At their most recent update on Oct. 30, the USDA Animal and Plant Health Inspection Service (APHIS) reported that 566 cases of equine WNV had been confirmed nationwide since the start of the year; in that same time span, 195 EEE cases had been diagnosed. As of Nov. 6, the United States Geological Survey (USGS) disease maps indicated that the WNV and EEE totals had risen to 620 and 204, respectively.

At most recent update, the USGS reported that Texas (100 cases), Louisiana (62 cases), Pennsylvania (50 cases), and California (45 cases) have tallied the most WNV cases this year. Louisiana (56 cases), Mississippi (31 cases), and Florida (29 cases) have reported the most EEE cases, also according to the USGS.

Another mosquito-borne disease, Western equine encephalitis, has not been identified in the United States this year.

According to APHIS disease maps, 2012 has seen the most WNV cases confirmed in the United States since 2006 when 1,086 cases were confirmed nationwide. The EEE case total has risen to more than triple last year's total (60 cases); however, it is still lower than the 247 and 301 cases seen in 2010 and 2009, respectively.

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 the 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.