Equine injections signal West Nile season’s start

April 19, 2005
Veterinarian Lise Andersen had never heard of West Nile virus until six years ago, shortly after it crept into the United States. Today, it’s part of her everyday life, and never more so than during the spring.
The hundreds of horses under her care are vaccinated against the virus every spring, a few weeks before mosquito season starts. Monday morning, she and Rocky Mountain Equine Clinic owner Jack Galt vaccinated about 40 of them at Mark Reyner Stables. “We like to have horses vaccinated before mosquitoes start showing up,” Andersen said. “It generally takes two weeks for the immune system to react to the vaccination. Vaccinating them now should cover them through mosquito season.” Horses have proved highly susceptible to the mosquito-borne virus. Like humans, they can’t transmit the virus, but it’s potentially fatal to those that are infected. A horse was El Paso County’s first West Nile virus victim of the 2004 season. The horse, which had not been vaccinated, did not die. Two people contracted the virus in El Paso County last year; neither died. Several people who own horses boarded at the city stables said they’re not worried their animals will contract West Nile virus. Vaccinating for West Nile virus has become a matter of course. County Health Department officials said the severity of this year’s season hinges on the weather. Wet weather means plenty of standing water —prime breeding grounds for mosquitoes. Connie Dodge, who watched Monday as veterinarians gave her horse, Red, a shot in the neck, said the horse is better protected than she is. “I’m not vaccinated against West Nile,” she said, laughing. No vaccine exists for humans, though Dodge — like many people —wears plenty of insect repellent to ward off the mosquitoes. A West Nile virus infection has never been recorded at Mark Reyner Stables in Palmer Park, and Andersen credits the owners for their insistence that horses are regularly vaccinated. “Everyone on the premises has to have a West Nile vaccination,” said stable owner Nancy Harrison. It’s among many steps she takes to keep the horses safe. “We make sure there’s no standing water,” she said. “We clean the water tanks with Clorox. If we get rain, I go in and sweep the water out of the pens. In the springtime, I’m down here sweeping (water) every day.” The mortality rate for horses infected with West Nile virus is high; one in three that contract it dies. “The vaccine is 94 to 96 percent effective, but it is not a guarantee your horse is not going to get West Nile,” Andersen said. If a vaccinated horse contracts the virus, however, it typically will display no more than mild symptoms. In 2004, two El Paso County horses tested positive for the virus, according to the El Paso County Department of Health and Environment. Twenty-five tested positive in 2003; six in 2002. Symptoms of West Nile in a horse include high temperature, stumbling, lack of coordination, weakness or partial paralysis. The symptoms are similar to those associated with equine encephalitis, another mosquito-borne disease. CONTACT THE WRITER: 476-4817 or jreuter@gazette.com
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