SOUTH DAKOTA ANIMAL INDUSTRY BOARD
FOR RELEASE
SAM D HOLLAND, DVM
SOUTH DAKOTA STATE VETERINARIAN
773-3321
July 29, 2002

West Nile Virus detected in SD horses

The South Dakota Animal Industry Board announced today that West Nile Virus had been diagnosed in 2 horses. Laboratory results reported late Friday indicated the disease in a Marshall County horse that was lost on Wednesday July 24^th. On Saturday laboratory results reported West Nile Virus for a Kingsbury County horse.

Neither of the affected horses nor any of the horses on the affected farms had been vaccinated for West Nile Virus.

The Marshall County horse was a 6-year-old draft breed mare and the Kingsbury County horse is a 3-year-old Haflinger gelding. Both horses were showing signs of abnormal behavior including incoordination and partial to complete paralysis.

South Dakota is the 8^th state to report West Nile Virus in horses in 2002 and joins Florida, Kentucky, Louisiana, Minnesota, Mississippi, North Dakota, and Texas. A total of 39 horses have now been confirmed with West Nile Virus in the US in 2002. Over 700 cases of West Nile Virus in horses were reported in the US in 2001, primarily in the Southeast part of the US.

"It is not surprising to see the disease appear in horses here" says Dr. Sam Holland, State Veterinarian. "We’ve seen the virus move westward since it was first identified in birds in New York in 1999, and have been aware that the virus is in our neighboring states to the North, South and East".

West Nile Virus is not a contagious disease from horse to horse so there is no quarantine issued for this disease. West Nile Virus is carried from birds, which act as the reservoir, and spread to other animals by mosquitoes which become infected feeding on an infected bird and then feeding on other animals such as the horse. Horses are susceptible to West Nile Virus encephalitis and the disease can be confused with western encephalitis or sleeping sickness, which has existed in South Dakota in the past.

"While only a few horses that are exposed seem to become infected, of those that do, the death rate can be as high as 30% with little treatment options available. For this reason horse owners are encouraged to consult their veterinarian and get their horses vaccinated. West Nile Virus vaccine is conditionally licensed and studies show a minimum of 2 doses at 3-4 week intervals are required for protection," says Dr. Holland.