Two more horses were found to have tested positive for West Nile virus in Marion County, Fla., the week of Sept. 9, which brings the total number of confirmed cases to 16 for 2002. Last year, there were 66 cases.Though the number is down considerably from 2001, it could pick up in September and October, health officials said."The peak for the presence of West Nile virus cases was from mid-September until about the end of October last year," said Dr. Maureen Long, assistant professor of large animal medicine at the University of Florida. "We saw an almost exponential increase in the number of cases at this time last year. Horse owners should not only be vaccinating for West Nile virus but for rabies and Eastern equine encephalitis."We've seen a decrease in the numbers of West Nile in some of the northern counties. Each year, we'll probably start to see fewer cases because many of the horses will have already been exposed to the virus. There will always be a West Nile virus presence in Florida because of migratory birds. The resident bird population that's already exposed to the disease will develop an immunity, which will help result in suppression of West Nile."Last year the United States Department of Agriculture Animal Health and Plant Inspection Service's data confirmed 89 horses were infected within the county, which includes Ocala. Veterinarians emphasize that horse owners should take the proper precautions."It's important to get your horses vaccinated," said Dr. Michael Jeter, diagnostic veterinary manager of the Florida Department of Agriculture and Consumer Services.