Researchers, Vets, Others Discuss West Nile Virus

Researchers, government officials, and private practitioners who are members of the Emerging Diseases Committee met at the Kentucky Livestock Disease Diagnostic Center for nearly two hours Friday to discuss how to handle information dissemination to veterinarians and horse owners on West Nile Virus (WNV) in Kentucky. The appearance of WNV in the state was not unexpected, and preparations had already been made where possible to fight this spreading disease.

One of the most important messages to the public is that WNV cannot be spread from an infected horse to any other creature, including other horses or humans. The only way the virus can be spread is by a mosquito first biting an infected bird, then biting another animal (such as a horse or human).

Veterinarians say this is one of those rare situations where the horse is actually in better shape to fight this problem than the human. While both are susceptible to the disease, there is a recently approved vaccine against WNV for the horse. There is no WNV vaccine for humans.

"We have a vaccine that we hope is effective, and we are going to use it," said Dr. Roger Murphy, a private practitioner who is president of the Kentucky Association of Equine Practitioners and the Kentucky Veterinary Medical Association.

However, it is important for all species that an extensive mosquito eradication program be undertaken immediately, according to the researchers and veterinarians.

"Only 1% of mosquitoes are carriers of this virus, and of those humans bitten by carrier mosquitoes, only 1% develop a serious illness," said Dr. Barry Meade of the USDA office in Frankfort, Ky.

"We can't control the birds, so we must control the mosquitoes and vaccinate," added Dr. Peter Timoney, head of the University of Kentucky's Gluck Equine Research Center.

Murphy said that some of the VNV vaccine manufactured by Fort Dodge Animal Health was delivered Friday to Kentucky. "I started vaccinating today," he said. "With a 10% mortality rate (death rate for horses which become ill with WNV), it's the smart thing to do."

Kentucky State Veterinarian Dr. Don Notter said that Fort Dodge shipped 250,000 doses of vaccine from its manufacturing plant Thursday to various parts of the country. He said another 500,000 doses should be ready for shipment by Sept. 15.

"This was unusual in that we didn't identify the circulating virus in bird first," said Notter. "But it's here, we've got it, and we have to deal with it."

No Restrictions, But Recommendations

At this point, there are no European restrictions on the movement of horses because of West Nile virus, said Meade.

Argentina requires that a horse imported from the United States "does (do) not proceed from, and during the 30 days prior to export, has (have) not stayed in, a State affected by West Nile virus." The regulations have a statement on Eastern and Western equine encephalomyelitis, requiring that the horses be vaccinated by a USDA-licensed, killed-virus vaccine.

"If the vaccine is used, we are encouraging veterinarians to document dates, horse identification, and serial numbers (from the vaccine vial)" just in case there is some request for proof of vaccination for horses that might be exported," Meade said. "We are recommending while awaiting word from Europe that if you anticipate a horse might be an export candidate, draw blood and bank the serum just in case we have to have proof of a previous negative status prior to vaccination," added Meade.