Infected horses present with ataxia, which is a lack of voluntary coordination of muscle movements.
Five cases have been confirmed in Kentucky and six have been confirmed in California.
The Arabian colt from Scott County received a vaccination in March, but did not receive a follow-up booster.
EEE and WNV have stricken hundreds of horses in Wisconsin since 2001.
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More than 70 equine West Nile virus cases have already been diagnosed in the United States in 2012.
A horse in Jackson County has tested positive for WNV, the first in the state to do so since 2010.
An unvaccinated 16-month-old Tennessee Walking Horse colt from Warren County tested positive today.
The WNV positive horses are from Fremont, Weld, Montrose (2), and Larimer counties.
The affected horse–an 18-year-old Tennessee Walking Horse from Laurel County–had no WNV vaccination history.
An 11-year-old Quarter Horse mare from Salem County has tested positive for West Nile virus (WNV).
Two horses from Johnson County, Iowa, have tested positive for West Nile virus.
The 3-year-old unvaccinated filly from Fresno County is recovering, the CDFA said.
The affected horse was not vaccinated against WNV and has since been euthanized.
All three confirmed WNV cases were unvaccinated, the CDFA reported.
The 2-year-old unvaccinated filly began displaying severe neurologic signs was euthanized.
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