West Nile virus strikes four horses in Maryland

Outbreak of concern to breeding industry

September 27, 2001|By Michael Stroh | Michael Stroh,SUN STAFF

Four horses in Maryland have tested positive for the West Nile virus, state agriculture officials said yesterday, marking the first time the disease has been detected in the state's equine population.

None of the infected horses -- three in Baltimore County and one in Cecil County -- died.

Although the disease's arrival had been anticipated by veterinarians, the news that it's finally here has alarmed some horse owners. Horse breeding is a multimillion-dollar industry in Maryland, home to more than 14,000 thoroughbreds, according to the Maryland Horse Breeders Association.

"Obviously, we've been worrying about it," said farm manager Jim Steele of Shamrock Farm, which has 90 horses on its 640 acres in Carroll County. "I don't think people thought it was going to happen this year."

The infected horses were mostly older animals kept as pets: a 27-year-old Tennessee walking horse in Kingsville, a 10-year-old Appaloosa mare in Perry Hall, a 30-year-old thoroughbred in Monkton, and a thoroughbred yearling in Chesapeake City.

State officials are awaiting final confirmation of the diagnosis from the U.S. Department of Agriculture. And they say they wouldn't be surprised if more West Nile cases turn up this year. "It's here to stay and spreading widely geographically," said Dr. Roger E. Olson, the state veterinarian.

West Nile is transmitted from birds to people and horses by the bite of mosquitoes. There is no evidence the virus can spread from horse to horse or horse to human.

The virus is most likely to sicken older animals, but young horses can die from West Nile too, said Dr. Randall L. Crom of the USDA's Animal and Plant Health Inspection Service.

The disease becomes a threat to horses when the virus moves into the brain, causing it or the spinal cord to swell. Symptoms include a wobbly gait, stumbling or a droopy lip.

The West Nile virus has infected 113 horses in the United States this year, according to the USDA. The majority of cases --88 -- have occurred in Florida. Twenty-six of the infected animals died or had to be destroyed.

Although an equine West Nile epidemic like the one seen in Florida is considered unlikely, any new disease that can kill a horse potentially could have devastating economic consequences. "Some of the horses I have, they can't be replaced," says Mike Pons, business manager of his family's Country Life Farm near Bel Air.

Among the 50 horses on Pons' farm are animals such as Allen's Prospect, Maryland's top sire. The stallion commands a stud fee of $12,500 and breeds with 100 mares a year.

But the consequences of a major outbreak are not only economic. The majority of the state's more than 45,000 horses are beloved pets.

"When those people experience a loss," says Steele, of Shamrock Farm, "that's part of the family."

Maryland's weather provides one defense against a major outbreak, officials say. The peak of the equine West Nile season is mid-September to mid-October. But in Maryland, that's when mosquito reproduction declines. The first freeze, usually in late October, should kill off any remaining mosquitoes.

Another defense is the new equine West Nile vaccine that the USDA approved Aug. 1. (A human vaccine has not been developed.)

At Manor Equine Hospital in Monkton, veterinarian Dr. Amy C. Polkes and her colleagues have run through their initial supply of 200 doses and ordered 500 more.

Fort Dodge Animal Health, maker of the vaccine, has shipped 35,000 doses to Maryland, said spokeswoman Laura Primm.

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