Horses may be at risk for diseases

PENNSYLVANIA FURNACE – Does Lyme disease occur in horses?

Dr. Jacob Werner, assistant professor of veterinary medicine and dairy and animal sciences at Penn State University, says “maybe.”

Werner discussed this and other insect-borne diseases last week during Penn State’s Ag Progress Days, held in Pennsylvania Furnace.

“I can experimentally develop Lyme disease in a horse,” he said, explaining that the horse’s body recognizes something foreign in its system and develops antibodies to fight it.

However, in the United Kingdom, most seropositive animals – horses that test positive for the disease – do not show clinical signs of illness, he said.

Werner said horses that test positive may have a fever, stiffness, lameness, muscle tenderness, unusual skin sensitivity, swollen joints or behavioral symptoms. But these symptoms may be indicative of a number of other diseases too, he said.

Horses diagnosed with Lyme disease – transmitted by deer ticks – are given an antibiotic specific to treating the illness.

“And they get better, so we assume that was the disease,” Werner said.

But the symptoms and improvement may be related to another undiagnosed illness.

“So the jury is still out,” he said, adding that there is no new evidence to suggest Lyme disease causes illness in horses, but no evidence against it.

Werner said the best course of action for horse owners is prevention. Weedy pastures should be mowed to reduce mouse populations, therefore reducing the number of ticks present. There are also repellent sprays on the market to prevent tick attachment, he said. Horses should be inspected regularly for ticks.

In the tropics and subtropics of the world, equine piroplasmosis, a tick-borne disease transmitted by the lone star tick, is prevalent. Werner said infection causes destruction of red blood cells, resulting in lethargy and jaundice. The disease is dangerous and highly transmissible, he said.

Piroplasmosis is typically found in other parts of the world, but 12 cases were reported in the United States in 2009. Many states, including Pennsylvania, have since instated mandatory testing for horses imported from Texas, where the lone star tick originates, and other states with known cases.

Though no cases have been confirmed in Pennsylvania, Werner said knowledge of the disease is important for horse enthusiasts who may purchase a horse from another state, travel out of state with their horse or be housed with horses that have been traveling.

“Make sure you’re sure of (state) requirements,” Werner said. “If this gets into our tick population, we can’t get rid of it.”

If an infected animal is found in a “piro-free” region, the horse must be quarantined. Current treatments are ineffective in clearing the disease entirely, but they can suppress clinical signs.