Many Marion County, Fla., horse farm owners took the advice of their veterinarians seriously and vaccinated their horses against the vector-borne West Nile virus last autumn. It has resulted in a decrease in the number of cases in 2002.According to statistics from the United States Department of Agriculture Animal and Plant Health Inspection Service, 89 horses had reportedly tested positive for the virus in Marion County in 2001. The numbers are way down for this year."We've only had six horses test positive for the virus in Marion County in 2002, and five of those horses hadn't been vaccinated," Marion County Department of Health nursing director Carol Jubelirer said.Farms continue to make sure their horses are inoculated against the virus. "We started vaccinating against the virus about a year ago, at the recommendation of our veterinarians," Live Oak Stud and Live Oak Plantation general manager Bert Mickel said. "We've sprayed around the barns and buildings for mosquitoes, and have taken the necessary precautions for prevention."The threat remains, and even though many horse owners in Central Florida have taken the proper precautions, other parts of the state have shown an increase in the number of horses that have contracted the disease, said Dr. Lee Coffman, Florida Department of Agriculture and Consumer Services director of the division of animal industry."We're experiencing a less severe impact in Northern Florida this year," Coffman said. "There's not as much activity in the North as there is in the South. The threat of the virus is very real, and we recommend that all owners statewide vaccinate. The horses that have died and suffered significant clinical signs weren't vaccinated. This virus will reach every part of the United States."