West Nile Virus Update for 2001

Horses in Alabama, Virginia, and Louisiana have been battling West Nile virus (WNV) for the first time since it hit the Western Hemisphere in 1999. In the meantime, veterinarians, public health officials, and horse owners are anticipating the first "killing frost," which will ideally exterminate most of the 2001 mosquito population--and the diseases that accompany them--until next year. Mosquitoes bite WNV-infected birds and pass the disease to horses and humans.

"We should begin to see fewer WNV cases in the wild bird population," said Tony Frazier, DVM, Alabama state veterinarian. "We're expecting drier conditions in Alabama (mosquitoes breed in areas with standing water), the weather has cooled some, and the mosquito population has decreased as well."

But not all states are guaranteed the four to five months of asylum from mosquitoes that most states enjoy with the coming of winter. William C. Jeter, DVM, Diagnostic Veterinary Manager for Florida's Division of Animal Industry said, "Sometimes we have a frost in late December, but we don't look for any dramatic change like up North when you start having really cold weather. It depends on what kind of a winter we have--if we have a mild winter, the mosquitoes survive."

Visitors--tourists and A-rated show riders alike--flock to sunny Florida for the pleasant temperatures, and the state likely will fight WNV through the winter. The virus has hit the Florida equine population hard this year, killing at least 21 horses and infecting up to 106.

"Of those 106 cases, we've been able to confirm that 80 horses are still alive, 21 (about 20%) are dead, and five unknown," said Jeter. He added that 82% of the cases have occurred in Jefferson County (where WNV first appeared in Florida) and adjacent counties.

How is the state coping with the threat of WNV? "Everyone seems to be doing all right--if it was more deadly like Eastern equine encephalitis, there would be more panic. I'm more concerned about people getting their horses vaccinated for Eastern/Western (encephalitis)."

At press time, 217 WNV-positive dead birds had been found in Florida in 38 counties (Florida has 68 counties). "We know the virus is out there in the counties (in birds), and it's just going to be a matter of time before it spills over into the horses and people (in currently unaffected populations)."

Vaccine Update

The Fort Dodge Animal Health WNV vaccine was approved Aug. 1, and veterinarians quickly exhausted available supplies. Reportedly, 100,000 more doses of the vaccine were to be dispensed the first week of November.

The verdict on the vaccine isn't in yet. "I think there might be a false sense of security in the WNV vaccine," said Jeter. "We hope it will do the job, but it's too early to tell. We're still seeing a few cases around, but we rarely have time to go back and do retrospective studies to see if the vaccine was giving protection to animals."

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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