West Nile Will Be Gone with Frost

West Nile Will Be Gone with Frost

On a clear September evening, Katherine Slover called her five horses in from the pasture. Four ambled toward the barn, long shadows following them, one, then another, then two more.

But where was Bob?

Slover had already called the veterinarian after noticing that Bob, a behemoth of a horse, appeared off his routine behavior. When Slover went to the pasture to look for her horse she found him standing wobbly on his feet, head down and dull-eyed.

That evening, Slover's 19-year-old gelding became one of the first equines in Potomac to be diagnosed with the West Nile virus. Because Slover acted immediately, Bob will make a full recovery.

“People who know their animals, and most do, realize when something is not right. A quick phone call can sometimes result in an animal making it or not,” she said.

Slover fed Bob 10 jars of applesauce a day for two weeks in order to keep Bob hydrated and prevent colic, since Bob would not eat while he was sick. Slover’s grocery trip cleared the shelves of Safeway and Giant.

“He needed lots of hands-on care because he was uncomfortable and had to be watched constantly so that he would not hurt himself,” she said. “He loved it.”

West Nile Virus first appeared in the northeastern United States in 1999 after large numbers of birds were found dead and tested positive for the virus. West Nile is a mosquito-borne disease that is transmitted when the insect feeds on infected birds. Once infected, the mosquito can transmit the virus to humans and other animals. The virus then multiplies and may or may not cause illness, depending on immunity of the individual.

According to the Centers for Disease Control & Prevention, in 2002 there were 4,156 reported human cases of West Nile, with the virus reaching 44 states. Although there is not a vaccine for humans, a vaccine has been developed for horses. It is 90-percent successful in protecting horses against the West Nile virus, said Dr. Peter O'Halloran of Monocacy Equine Veterinary Associates in Beallsville, who cares for many Potomac horses. “Monocacy has not seen a case in a properly vaccinated horse, although this is just in our practice,” he said.

But the infection could occur in vaccinated, immune-suppressed or sickly horses, said Belinda Thompson, senior extension veterinarian at the College of Veterinary Medicine at Cornell University. The vaccine has an 80 to 90 percent protection rate in most horses, depending on their health and the amount of exposure.

Bob, who has multiple and often debilitating allergies, was especially vulnerable to the virus. Cyrus Lesser, chief of the Maryland Department of Agriculture’s Mosquito Control Section, said that in a heavily infected area, as many as a thousand mosquitoes could bite a horse and just the sheer numbers might give it a giant dose of the virus, overwhelming the vaccine.

“But I can't imagine why horse owners, after this wet year, wouldn't take the precaution of vaccinating their horses,” he said.

Lesser refutes the negative information on the Internet about the vaccine, which tends to discourage horse owners from vaccinating.

“We know that 90 percent protection is a good effectiveness,” he said. He recommends giving horses a booster every 90 days in areas where the threat of infection remains because there is no frost.

The infection in horses causes an inflammation of the brain and sometimes the spinal cord, resulting in the stumbling and lack of coordination that Slover witnessed in Bob. Horses also may exhibit signs of depression, an inability to stand upright and weakness in the limbs. Muscle twitching, especially around the muzzle, is also a sign.

But Bob was not the only victim of West Nile in Potomac. Last year, a human member of Slover's household also contracted the West Nile Virus.

Two years ago, at Congressional Country Club, as well as at the Slover farm, flocks of crows disappeared. “Our population has definitely declined,” said Mike Giuffre, the groundskeeper at Congressional.

MARYLAND STOPPED PICKING up bird carcasses, said Fidelis Hegngi, the Assistant State Veterinarian for Maryland. “That kind of testing isn't necessary now because we know what we are dealing with,” he said. “The incidence of WNV is definitely up this year, but we knew this would happen because of the rain.”

Hegngi added that 88 horses in Montgomery County tested positive for West Nile virus so far this year.

All horse owners are advised to give one vaccination in April or May and follow up with a booster six weeks later, said O'Halloran. The first shot primes the immune system to the virus and the second establishes a protective level of antibodies to fight off the virus.

“So far our vaccination program has provided a good protection from West Nile,” he said.

But prevention — keeping horses and humans as mosquito-free as possible — is an important factor in avoiding infection. “We would like to see close to 100 percent vaccinated in this area next year,” said O'Halloran. He advises that it is not too late to vaccinate horses now because the threat of West Nile will remain until the first hard frost.