WEST NILE VIRUS

     This disease is a neurologic disease caused by a virus spread by mosquitos.  Similar to the encephalitis virus, it can infect horses and rarely humans.  It also infects and kills birds which often act as sentinels, letting us know that the virus is in a certain area.

     Not long ago dead crows were found in the Milwaukee area that are strongly suspected to be infected with the West Nile virus.  No horses have been suspected of having West Nile in Wisconsin.

     In 1999 this virus appeared for the first time in the United States, in eastern New York and Delaware.  In the late summer of 2000 it spread down the eastern coast. In 2001 it showed up in several midwest states including Indiana, Michigan, and Wisconsin.  That year in the United States there were thirty five (35) cases in horses and twelve have died or were euthanized.  Not all horses exposed will develop signs.  In those that do, signs are neurologic and include stumbling, lack of coordination and paralysis. Most do not have fevers.

     Prevention is the key to controlling this disease . Keep horses stabled at dusk during high levels of mosquito feeding, remove any standing water where mosquitos can breed, and use mosquito repellants like Duocide large animal spray or human sprays.

     There is an effective vaccine that should be administered each spring.  Horses traveling south for the winter months should be boosted in the fall.  Despite some controversy, it is believed to be safe for use in pregnant mares.