A year-old thoroughbred filly in St. Tammany Parish tested positive for West Nile virus in mid-July, according to Mike Strain, Louisiana Agriculture and Forestry Commissioner.

“This is the first case of West Nile virus in horses this year,” Strain said. “I can’t stress enough the importance of vaccinating your horses for West Nile virus and also Eastern equine encephalitis (EEE). Both are mosquito-borne diseases but vaccination is the key to preventing these illnesses and protecting your animals.”

Mississippi veterinarian Dean Stringfellow diagnosed the filly, domiciled in Pearl River, with West Nile virus. Stringfellow said blood samples sent to the Mississippi Veterinary Diagnostic Laboratory confirmed the presence of the disease.

Stringfellow said the Pearl River horse is recovering, but Strain said 10 Louisiana horses diagnosed and confirmed with EEE in 2009 have all died.

“Both diseases can cause problems in horses but EEE is almost always fatal,” said Strain. “We’ve notified the St. Tammany Parish mosquito control unit of the West Nile virus case.”

The Culex mosquito infects horses with the West Nile fever flavivirus while EEE is spread by the Culiseta and Aedes mosquitoes. Neither disease is spread from horse to human.

A horse infected with West Nile virus may exhibit a variety of symptoms including colic, lameness, anorexia and fever. Initial signs include a mild low-grade fever, feed refusal, and depression.

EEE symptoms include high temperature, depression, development of a sleepy appearance and walking in circles. The infected horse eventually collapses to the ground.

More than 300 confirmed cases of West Nile fever were reported in 2002 in Louisiana. Since vaccine development, confirmed cases have averaged a little over 30 per year since 2003.

Henry Moreau, state veterinarian of the Louisiana Department of Agriculture and Forestry, said horse owners should contact their local veterinarian for proper vaccination scheduling.

Any suspected cases of West Nile virus and EEE should be reported to the LDAF’s Office of Animal Health Services at (225)925-3980.