In 1999, West Nile virus was found for the first time in the United States. Since that time, numerous species of animals have tested positive for the virus.  The types and numbers of animals that have tested positive for WNV in Pennsylvania can be seen in the table below.

Mosquitoes acquire the virus from infected birds and pass it on to other birds, animals and people.

There are two vaccines available for horses to prevent West Nile Virus. In addition, specific treatments are now available for horses if West Nile is diagnosed early.

Clinical signs most commonly reported in horses ill from WNV infection in Pennsylvania include:

-weakness, especially in the hind end
-stumbling, incoordination
-down, difficulty rising without assistance
-hypersensitivity around the head
-muscle and muzzle twitching
-mild fever
-lethargy

For more information, contact your veterinarian or the Department of Agriculture's Bureau of Animal Health and Diagnostic Services at 717-772-2852.