Potomac Horse Fever: A Serious Equine Disease

Potomac horse fever is a potentially fatal equine disease caused by a bacterial infection acquired through ingestion of infected aquatic insects.

Key Facts

Potomac horse fever is caused by Neorickettsia risticii, an intracellular bacterium
Horses become infected by ingesting aquatic insects or their larval stages near water sources
Clinical signs include severe diarrhea, fever, depression, and laminitis
Mortality rates reach 5-30% without prompt treatment
The disease occurs most commonly in summer and fall near rivers and streams
Vaccination is available but provides only partial protection

Welfare Considerations

Potomac horse fever causes significant suffering when it strikes. The diarrhea produced is profuse and painful, and affected horses become profoundly depressed and refuse food and water. A particularly devastating complication is laminitis - painful inflammation of the feet - which can develop during the illness and persist long after recovery from the primary infection. Horses that develop severe laminitis as a complication may require prolonged, intensive management and in severe cases may not recover full soundness. Rapid diagnosis and aggressive treatment with appropriate antibiotics and supportive care are critical welfare interventions that significantly improve outcomes.

What You Can Do

Vaccinate horses in endemic areas and consult vets about timing near water sources
Reduce horse access to stagnant water or areas with abundant aquatic insects
Monitor horses closely in summer and fall for fever, diarrhea, or depression
Seek immediate veterinary care if Potomac fever is suspected
Implement preventive hoof care and monitoring during illness to detect early laminitis