PENNSYLVANIA FURNACE - Ticks aren't the only pest to cause worry for horse owners.
Dr. Jacob Werner, assistant professor of veterinary medicine and dairy and animal sciences at Penn State University, said horses are prone to a number of diseases caused by other animals.
Freshwater snails carry Potomac horse fever, which can be transmitted when a horse unintentionally ingests an infected snail in the pasture. Werner said horses that live in areas with standing water or a pond nearby are most susceptible to the disease.
Horse fever has been reported in the United States and Canada, and infected horses often show signs of high fever, diarrhea and laminitis. Werner said the illness may cause abortion in pregnant mares.
"These animals get pretty darn sick," he said.
Horse fever can be treated with antibiotics and supportive therapy, and vaccinations are available in some areas. However, prevention is the most effective way to keep the disease at bay. Werner said horse owners can reduce exposure to the snails by installing netting around areas of standing water, reducing night lights and using insecticides.
Mosquitoes that carry West Nile Virus are also a threat to horses, he said.
The first U.S. cases of West Nile infecting humans or animals were reported in 1999 in New York. Just three years after that, 15,257 cases were reported nationwide, Werner said.
Werner said there is a 28 to 38 percent mortality rate in horses that show clinical signs of disease - fever, anorexia, depression, gait change, hyperexciteability or aggression.
Once clinical signs appear, symptoms often get worse for seven to eight days before they improve, Werner said. Horses must be stabilized and treated as soon as possible. If a horse's condition can be stabilized, Werner said, it has a 90 percent chance of full recovery within six months. If not stabilized, horses often die or must be euthanized.
Werner said the virus can be prevented by controlling mosquito populations, which typically peak in July through October in central Pennsylvania.