A horse admitted to the College of Veterinary Medicine Large Animal Hospital at Purdue University in mid-June has been diagnosed with Potomac horse fever. Ordinarily, cases of Potomac horse fever don't show up in Indiana until July or August.
According to Janice E. Kritchevsky, DVM, and professor of large animal internal medicine at Purdue University, horse owners and equine-housing facilities should be on the lookout for symptoms of Potomac Horse Fever, a bacterial disease that can lead to serious health conditions or death.
Aquatic insects-cause of Potomac horse fever
Early case of Potomac horse fever could mean that the mild winter and spring will lead to more cases with insect populations running about three weeks early.
Dr. Kritchevsky noted, "This early case could mean that the mild winter and spring will lead to more cases of the disease this summer."Most insect populations are running about three weeks early, said Tom Turpin, Purdue Extension entomologist. "It doesn't surprise me that a disease with an insect vector, or immediate host, is showing up early as well," he said.
The cause of Potomac horse fever, N risticii has been identified in freshwater snails and isolated from trematodes released by the snails. It has also been detected in up to 14 species of insects and flies, including mayflies and dragonflies. One route of exposure is believed to be the inadvertent ingestion of aquatic insects that carry the causative agent in the stage of the trematode.
The causative agent is present in the feces of experimentally-infected horses, but clinically ill horses are not contagious and can be housed with healthy horses. If more than one horse at the same location contracts the disease, it is because of the environmental conditions that draw the vectors.
The disease causes colitis, dehydration and diarrhea. Without treatment, which includes tetracycline-based antibiotics, intravenous fluids and anti-inflammatory agents, the disease can lead to shock, permanent lameness or even death.
Purdue's Large Animal Hospital treats horses with Potomac Horse Fever every year. When complications such as founder have occurred, horses have had to be euthanized. The horse admitted to the hospital in June recovered and has been discharged.