Fifty-nine equine cases of West Nile virus (WNV) were confirmed last year in the Northeast. Officials at Fort Dodge Animal Health’s laboratories in Kansas City, Mo., have been working diligently to develop a WNV vaccine for veterinary use, and potentially help prevent the virus from appearing in horses in 2001.

West Nile made its Western Hemisphere debut in the summer and fall of 1999, attacking birds, horses, and hu-mans. The United States Department of Agriculture’s (USDA)

Animal and Plant Health Inspection Service (APHIS) reported 25 equine positives in 1999, nine of which died or were euthanized. Of the 59 (reported) cases in 2000, 23 died or were euthanized (39%). WNV is spread by the bite of an infected mosquito, and was found in 2000 as far south as North Carolina in birds, and as far west as Erie County, Pa., in mosquito pools. It’s not about “if” the disease is going to spread in 2001, it’s about when and where, and how veterinarians and horse owners can be prepared should it arrive in their pastures.

“We’re fairly certain that we’re going to have West Nile activity again in 2001 in horses,” said Randall Crom, DVM, staff veterinarian and coordinator of WNV issues for APHIS. “What the extent of it will be and where are hard to predict. We have some good clues as to where it might be, based on where it has been the last two years and the progression of its spread.”

Fort Dodge obtained a sample of WNV soon after the virus had its debut in the states. Tom Overbay, DVM, Director of Professional Services at Fort Dodge, explained that since the virus is a human pathogen, vaccine development is under strict biosecurity. According to Crom and Overbay, before the vaccine can be released under a conditional license, it must be proven to be pure, safe, and have reasonable expectation of efficacy. Fort Dodge and the USDA have been working together since day one of the vaccine development. Fort Dodge hopes to develop a vaccine which will make it possible to continue to monitor the disease itself (differentiate vaccinated from naturally infected horses)