Jeff Raine, who manages the Big E farm in Jamesport, N.Y., where two horses, including a thoroughbred brood mare, succumbed to West Nile last year, said he was doing everything he could to prepare for mosquito season. The 120-acre breeding farm is owned by Robert Entenmann of the baked goods company, and is home to 15 horses that serve as Mr. Entenmann's private breeding and racing stock. Terroir's illness was the first confirmed case of equine West Nile in last year's outbreak, said Dr. John Andresen, the veterinarian who treated her and diagnosed her as having the virus. Government scientists are using genetic material from Terroir for research on a possible vaccine, he said. At Belmont and elsewhere, state officials are testing the blood of chickens, which carry the virus but do not get sick from it, for signs of West Nile.
Chickens can spread the virus to horses if mosquitoes bite infected chickens and then bite horses.
A group of chicks from Belmont who were tested recently showed no sign of exposure to the virus, said Dr. Neil Cleary, a veterinarian with the racing association who treated one of the two Belmont racehorses who was infected with West Nile but recovered. State officials said that since the outbreak, they have conducted blood tests on horses in the Riverhead area and across Long Island to determine how many were exposed to the disease, possibly making them immune. The incubation period is up to seven days, so those horses would not be at risk for infection, veterinarians said. But several experts said they suspected West Nile was carried to Riverhead, on the tip of the island, by birds. Dr. Andresen and other veterinarians who have studied the virus since last year's outbreak, the first time West Nile was detected in the Western Hemisphere, said the newness of the disease here made it difficult to understand the risks.