Disease again striking equine population

The north country may be seeing another outbreak of Potomac horse fever, a life-threatening gastrointestinal disease.

Outbreaks of the disease occurred in St. Lawrence and Jefferson counties in 2001 and 2004.

Veterinarian Kirsten D. Anderson of Lake Effect Veterinary Service, Watertown, said that in St. Lawrence County, she has treated "five to six ill horses in the last two weeks."

She said she hasn't seen any cases yet this year in Jefferson County.

Infected horses may experience fever, depression, miscarriages, rapid weight loss and a painful inflammation of the hooves, which often can be crippling.

Severe diarrhea also can occur, which could cause deadly dehydration if not treated.

The disease is believed to be transmitted when a horse accidentally ingests insects such as mayflies that are carrying a parasite known as Neorickettsia risticii. Snails and slugs are also a problem, since they can carry the parasite in their slime.

These pests thrive near water, which is a particular problem for the north country. Wet weather mixed with the area's abundance of rivers leaves huge swaths of the area susceptible to transmission.

"Having the wet season and then going so hot was definitely a breeding ground," said Corey M. Hayes, farm business management educator for Cornell Cooperative Extension of Jefferson County.

To reduce the chances of a horse becoming infected, it is important to make sure water buckets and feeding areas are clean, Mr. Hayes said. Covering food also is a good way to reduce the chances of accidental ingestion of insects or other carriers.

It also is important to check on horses daily because of the quick onset of symptoms. Potomac horse fever has an incubation period of 10 days.

"Horses in pasture must be checked every day," Dr. Anderson said.

She said that if a horse gets diarrhea, it could die of dehydration within a matter of days.

Treatment of infected horses should begin as soon as symptoms are noticed. Treatment with antibiotics costs an average of $500 to $2,000. Sick horses also are given fluids to help with dehydration.

Tetracycline antibiotics, such as doxycycline, are commonly used to treat the disease because of their effectiveness in killing the parasite.

A vaccination also is available that greatly reduces the chance of infection.

"Vaccination is key," Mr. Hayes said. "A $15 vaccination is a lot cheaper than $1,500 for supportive care."