Veterinarians at the Ohio State Veterinary Medical Center are warning horse owners that the fall season brings with it an increased risk of illness for the horses in Ohio and surrounding states. Potomac horse fever is one of several diseases that have their peak incidence in horse populations during this time of year, particularly those carried by insects.
Aquatic insects and snails as factors in horse disease
The fall season brings with it an increased risk of illness for the horses including Potomac horse fever which is one of the diseases that reach their peak in horses during this time of year.
Many horse owners are familiar with diseases carried by mosquitoes and ticks such as West Nile virus, eastern equine encephalitis, and Lyme disease; however, Potomac Horse Fever, a disease also transmitted by insects, is another serious threat to the health of horses and is often overlooked until it is too late.
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.
If a horse is showing signs consistent with PHF, a veterinarian can run tests to definitively diagnose the condition.Although treatment is often started before the results of these tests are complete, running them is still worth the extra effort and expense.
Having a confirmed diagnosis of PHF on a farm should encourage monitoring of other horses on the property for any evidence of infection, as early detection may save horses’ lives. Taking body temperatures at least once, preferably twice daily may be the best way to detect early Potomac Horse Fever. Any horses with fevers over 102 degrees F should receive veterinary evaluation as soon as possible.