Horse owners protecting their animals against equine West Nile

By: LORELL FLEMING - Staff Writer | Saturday, July 24, 2004 11:31 PM PDT ∞

NORTH COUNTY ---- With 30 cases of equine West Nile virus now confirmed in California, local horse owners say they are doing everything they can to protect their steeds from the potentially fatal disease.

The importance of those measures was underscored Thursday when San Diego County officials confirmed that a hawk found dead in Carlsbad was infected with the disease.

The hawk, discovered about three weeks ago near a home, is the first virus-infected bird found in the county this year. West Nile mainly affects birds, but can be spread to horses and humans by mosquitos who feed on dead birds who had the disease.

Horses are the domestic animal most susceptible to contracting West Nile virus, according to the California Department of Food and Agriculture. There are no documented cases of transmission of the disease from horse to human or to other horses, according to the U.S. Centers for Disease Control.

California has a high number of mosquito species that efficiently transmit the disease, a factor that officials say could mean that the West Nile virus will spread quickly.

Also on Thursday, authorities confirmed the state's first human fatality from the virus. The victim was a 57-year-old Orange County man. Thirty-five people in California have been infected with the virus this year, according to state health officials. Except for the Orange County man, all the cases were in Riverside, Los Angeles and San Bernardino counties.

The virus has been detected in 980 dead birds, 75 chickens throughout California as of Thursday, health officials said.

The 30 cases of equine West Nile virus confirmed as of Friday included 20 in Riverside County and 10 in San Bernardino County, according to the California Department of Health Services. Sixteen of the cases resulted in death, said Vicki Kramer, head of the department's vector-borne disease section. California only had one equine West Nile virus case last year.

Horses can be vaccinated from the disease, but it takes up to eight weeks to become effective.

"West Nile virus vaccinations for horses have never been more important," said California State Veterinarian Dr. Richard Breitmeyer. "If people get the necessary booster shots for their horses now, or even just start the vaccination series, horses that may otherwise die can still be protected this season. Horse owners should contact their veterinarian as soon as possible."

With the thoroughbred racing season starting last week at the Del Mar Thoroughbred Club, President and General Manager Joe Harper said he is not particularly concerned about the virus infecting the nearly 2,200 horses at the track during the season.

"About 99 percent of horses here have been vaccinated, and every horse here will be vaccinated," Harper said. "The (San Diego) county mosquito abatement program has picked up here, increasing the amount of spraying. The county has always been diligent about its mosquito abatement program.

"We're also doing an increased amount of spraying, not just on the track's backstretch, but any areas with standing water," Harper also said.

Education on the topic is the first step in keeping horses free of the disease, said Laura Rosier, head of security, health, and safety for San Luis Rey Downs Training Center in Bonsall. About 450 horses are kept at the center annually, with some increases during the Del Mar race season.

"We keep our horses on the recommended vaccination schedules, and we have horses wearing fly masks when the horses are out and it's hot. There is also fly netting if we need it," Rosier said. A fly mask is a netting draped over a horse's face. A fly sheet is netting that covers a horse's body.

Another precaution is to increase efforts to maintain clean and dry areas at the training center, since standing water is a breeding site for mosquito larvae, Rosier added.

Big operations such as the Del Mar racetrack and the Bonsall training center aren't the only places or people taking precautions against equine West Nile virus.

Fallbrook residents Linda Nickerson and her husband, Gerhard Kesslau, have nine miniature horses. Nickerson said she and Kesslau did away with big trough that was about 18 inches deep, four feet long, and about 24 inches wide.

"That's a lot of water that'll breed mosquito larvae," Nickerson said. When they used the trough, they added mosquito-eating fish into the water, but pulling the fish out with a net each time you emptied or cleaned the trough became tedious, she explained.

They recently installed a system that distributes drinking water for the horses, Nickerson said. The new system fills the horses drinking cups with about two inches of water at a time. As the horses drink, the cups automatically refill to that same level.

Even with that precaution plus vaccinations, Nickerson said she remains on the lookout for West Nile virus symptoms among her miniature horses.

Once a horse is infected, the virus multiplies in the horse's blood system and infects the brain causing inflammation and disrupting the central nervous system.

Signs of infection include stumbling, staggering, wobbling, weakness, muscle twitching or inability to stand. Among infected horses, about a third die or must be euthanized and another 17 percent are inflicted with long-term debilitation, according to the state agriculture department.

Contact staff writer Lorell Fleming at (760) 731-5798 or lfleming@nctimes.com.

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