Once considered a regional disease upon its discovery in 1979, Potomac horse fever has re-emerged during recent years in the equine community.
Potomac horse fever (PHF) originated near the Potomac River in the eastern United States but has been identified in various other regions of the United States and Canada. A seasonal disease, PHF occurs mostly between late spring and early fall in temperate areas. It is common in horses kept near rivers, streams or irrigated pastures as PHF originates in flatworms developed in aquatic snails. The immature flukes can be swallowed by the horses but are more commonly picked up by aquatic insects. PHF has also been found sporadically in dogs and cats.
Initial signs of PHF include depression and a transient high fever but can progress in seven to 10 days to loss of appetite; colic; loose manure to profuse, watery diarrhea; edema of the head, legs and abdomen and laminitis. Late-term abortions may happen in pregnant mares affected by PHF.
PHF has re-emerged in recent years as many areas of the country did not have any cases in a long time and vaccination rates declined. Multiple vaccines are available; while a vaccinated horse may still develop PHF, the disease will be a milder form. Testing for PHF is available, but the turn-around time for test results is generally longer than the seven to 10-day period when symptoms intensify to dangerous levels. As the flukes travel by aquatic insects, minimizing insect ingestion in stabled horses by turning off barn lights at night is recommended.
If you suspect PHF in your horse, contact us immediately to start a course of treatment.