West Nile, EEE reported across the U.S.

HorsePortrait_Shutterstock2469785_blogWith the approach of fall, reports of insect-borne diseases in horses have begun to pick up across the U.S.

As of September 3, 64 cases of equine West Nile Virus across 23 states have been reported to the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS). West Nile virus is spread by mosquitoes and is the main cause of arbovirus encephalitis in U.S. horses. Equine cases also account for almost 97 percent of non-human mammalian cases, according to the American Association of Equine Practitioners (AAEP).

Last year, there were a total of 627 equine cases of West Nile in the U.S., a drastic jump from only 87 in 2011 but much lower than the peak of 15,257 cases in 2002 (when looking at numbers from 1999 onward), according to APHIS. 2012 represented the most cases in the past five years and also correlated with an uptick in human cases.

The fatality rate for horses with West Nile is about 33 percent; however, about 40 percent of horses that recover may still exhibit aftereffects of the West Nile, such as abnormal gait and behavior,  six months later. Vaccination for West Nile is a core vaccine as recommended by AAEP.

Eastern equine encephalitis (EEE) cases also have been reported, with 77 in the U.S. as of September 4, according to the U.S. Geological Survey EEE page. Florida has the most reported cases with 28, with Georgia a close second with 20 cases. So far this year, there have been no confirmed reports of western equine encephalitis (WEE).

Like West Nile, EEE and WEE are transmitted by mosquitoes. Mortality for horses infected with EEE is about 90 percent and for WEE, it is about 50 percent. Vaccination against EEE and WEE also are considered core vaccines by AAEP.

Read more insect-borne diseases such as West Nile and EEE from Neogen’s Dr. Little here.

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