Kentucky has kept extensive statistics on West Nile virus cases in the state. At the March 7 West Nile Virus Workshop at the University of Kentucky's Gluck Equine Research Center, Rusty Ford, Kentucky Equine Programs Manager, reviewed equine WNV statistics from past years. He also described how the state planned to make reporting cases easier in 2003.
West Nile virus was first detected in horses in Kentucky in August of 2001. The mortality rate was 75% that year, but that rate dropped to 25.5% in 2002. The first equine case in 2002, a Thoroughbred yearling, was detected June 27 in the Central Kentucky area. "This was a young, healthy horse, and a vaccinated animal," he said, "We switched from offense to defense, because we had to defend what and where (these cases were), and the vaccine issue."
At the beginning of 2002, Ford forecast his thoughts for the number of WNV cases that might occur in Kentucky. "I wouldn1t be surprised if we1d have 50-60 cases," he said at the time. In reporting at the Gluck seminar, he chuckled at this prediction, for by the end of 2002, there were 513 equine cases of WNV in the state.
Ford said that by August of 2002, the virus was moving in all directions. "I knew my prediction of 50 cases was fixing to get blown apart," he said. "Couple that with the (number of positive) birds we were finding, and we knew we were going down a rocky road."
The weekend of Sept. 7, 2002, marked a peak in equine cases, just a few weeks after the peak of WNV-positive bird findings and human cases. By Oct. 3, there were 425 confirmed cases. In all, there were equine cases in 78 of the 120 counties in Kentucky.
Of the 513 cases, 376 (73%) survived, 104 (20%) were euthanized, and 33 (6%) died. The youngest horse affected was four months old, and the oldest was 33 years old.
"Ninety-seven percent of affected equines were not adequately vaccinated," he said. "Of 513 detected equines affected by WNV, 74 (14%) had received at least one dose of the vaccine. Of 17 horses that were properly vaccinated for WNV and yet contracted the disease, 14 horses survived," he said.
The question was, and continues to be, "Does the vaccine work?" Ford thinks it does, and Rob Keene, DVM, from Fort Dodge Animal Health, manufacturers of the WNV vaccine, spoke after Ford1s presentation (click here for a story on Keene's presentation).
Tracking cases of WNV in 2003 will be much easier, according to Ford, if veterinarians get better at listing specific information on the submission forms for suspect WNV cases. Often forms arrive with a veterinarian1s name and number, a date, and the age of the horse affected. If veterinarians list clinical signs, dates of onset, and outcome, it will save time for state officials and veterinarians. Ford said he spent countless hours on the phone in 2002 tracking cases because of paperwork that was filled out improperly.
Ford encouraged veterinarians to get on the Internet and brush up on their WNV knowledge so that they can discuss the disease and steps to prevention with their clients. These steps, beyond vaccination, include removal of standing water to reduce breeding grounds for mosquitoes. Ford said that the more rural areas of Kentucky are not as aware of the risk of the virus as other areas.
"We played defense in 2002, and I1m hoping we'll be able to play offense this year," he said. But he emphasized to veterinarians that the only way to do this is to gather information on WNV and share it with clients and fellow practitioners. He pointed veterinarians to the Kentucky Department of Agriculture's web site, http://www.kyagr.com/state_vet/ah.
"Sharing of information is going to be a deciding factor in whether we succeed or fail," said Ford.