Illinois Confirms First Equine WNV Case of 2012

According to information from the Illinois Department of Agriculture, a horse in Jackson County has tested positive for West Nile virus (WNV), the first in the state to do so since 2010. According to public health officials, the presence of the virus in horses can be an indicator of increased WNV risk for humans.

Jackson County Health Department participates in a statewide West Nile virus surveillance program that aims to detect the virus in mosquito, bird, horse, and human populations. The detection of WNV in other species indicates potential risk to humans of contracting the virus. Since mid-June the Health Department has detected West Nile virus in several batches of mosquitoes, one bird, and now has lab results from August 14 on a horse positive for the virus.

No human cases of WNV have been reported in Jackson County this year, although eleven human cases have been reported in Illinois recently, all of which are in the Chicago area. Thirty-seven Illinois counties have reported West Nile virus activity so far this year, compared to 19 counties for all of 2011.

According to Bart Hagston, environmental health director for Jackson County Health Department, "All of these surveillance results drive home the importance of people protecting themselves from mosquitoes. While birds and horses can be infected with West Nile virus, mosquitoes are the only creatures known to infect humans with the virus. It is important for everyone to take precautions against mosquito bites at this time."

Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia. Equine mortality rate can be as high as 30-40%.

The USDA Animal and Plant Health Inspection Service reported 87 cases of WNV in U.S. horses in 2011.

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