An alarming number of cases of severe diarrhea in horses have been noted in the Big Horn Basin over the last several weeks. Laboratory testing has confirmed that these horses have been affected with Potomac Horse Fever. Potomac Horse Fever is a bacterial infection caused by a Rickettsia bacterium. These bacteria are unique in that they invade the host and attack and live inside the host’s cells; this causes severe damage to the infected cells. With Potomac Horse Fever, the infection is in the cells of the colon. Once the cells are damaged, they cannot absorb water or nutrients resulting in severe diarrhea and extreme weight loss. The diarrhea can become so overwhelming that the horses actually die of dehydration.
Treatment of Potomac Horse Fever is primarily through the use of IV antibiotics. Other therapies can include probiotics to help combat the pathogenic bacteria with good bacteria, fluids to maintain hydration, acupuncture to slow down the diarrhea, and various other therapeutic combinations to control the presenting symptoms.
Controversy surrounds the use of antibiotics in the treatment of Potomac Horse Fever as several horses seem to have a longer course of the disease with initial improvement and then they undergo several bouts of recurrence. It is possible that the initial elimination of bacteria with the antibiotics keeps the horse from mounting a full immune response but does not result in a complete resolution of the disease.
Prevention is the best manner to keep your horse protected. The only way to prevent this severe illness is to vaccinate your horses. The Potomavac vaccine is available for the prevention of Potomac Horse Fever and should be administered yearly near the beginning of the summer. We recommend working with your veterinarian to determine a specific vaccination protocol for your horse.