Nationwide Equine EEE, WNV Case Totals Creeping Up

Nationwide Equine EEE, WNV Case Totals Creeping Up

Vaccinating horses against WNV and EEE coupled with mosquito control are the most important ways to minimize an animal's chances of becoming infected.

Photo: Anne M. Eberhardt/The Horse

Despite the fact that summer is over and fall has arrived, horses around the country continue testing positive for both Eastern equine encephalitis (EEE) and West Nile virus (WNV), according to recent updates to the U.S. Department of Agriculture Animal and Plant Health Inspection Service disease maps. Still, the number of confirmed cases of these mosquito-borne diseases remains below last year's totals.

As of Sept. 25, 21 states had reported 139 cases of EEE in horses. South Carolina and Florida have seen the most cases so far—36 and 28, respectively—with Georgia (20) and North Carolina (12) following behind. EEE cases have also been confirmed in Alabama (4), Arkansas (3), Connecticut (1), Delaware (1), Kentucky (1), Louisiana (6), Maine (3), Maryland (1), Massachusetts (4), Michigan (1), Mississippi (9), New Hampshire (1), New Jersey (3), New York (1), Texas (1), Vermont (2), and Virginia (1).

Last year, 209 cases of EEE were reported in horses nationwide, with Louisiana (55), Florida (34) and Mississippi (32) confirming the most cases.

Also as of Sept. 25, 157 cases of equine WNV had been reported in 28 states. Montana and Wyoming reported 17 and 11 cases, respectively, while Texas and California reported nine and eight cases each. Cases have also been reported in Arkansas (1), Colorado (3), Delaware (1), Florida (2), Georgia (2), Idaho (4), Illinois (2), Indiana (1), Iowa (5), Kentucky (2), Louisiana (2), Michigan (2), Minnesota (2), Mississippi (1), Missouri (3), Nebraska (3), New Mexico (3), New York (2), Ohio (1), Oklahoma (5), South Carolina (1), South Dakota (2), Utah (4), and Vermont (1).

Last year, 627 equine WNV cases were confirmed nationwide, the highest total since 2006 when 1,086 cases were confirmed. Texas was the most severely affected state in 2012.

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 reduce the chances these insects 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.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More