Potomac Horse Fever.
Authors: Taylor
Journal: The Veterinary clinics of North America. Equine practice
Summary
# Potomac Horse Fever: Two Pathogens, One Disease Potomac horse fever remains a significant cause of colitis in endemic regions, though our understanding of its aetiology has expanded considerably. Taylor's 2023 review documents the emergence of *Neorickettsia findlayensis* alongside the historically recognised *N. risticii* as causative agents, both transmitted via ingestion of infected trematodes within aquatic insects—a crucial epidemiological detail for understanding risk factors in affected properties. Clinical presentation is consistent across both pathogens: horses typically present with diarrhoea, fever, anorexia, lethargy and colic of variable severity. PCR testing of blood and faecal samples represents the gold standard for diagnosis, allowing practitioners to differentiate PHF from other causes of acute colitis. Whilst tetracycline therapy remains the cornerstone of antimicrobial management, the emphasis on aggressive supportive care—including fluid and colloid therapy, NSAIDs, endotoxin mitigation and digital cryotherapy—underscores that PHF management fundamentally mirrors treatment of severe colitis cases, with pharmacological therapy addressing the underlying infection whilst intensive nursing care determines clinical outcome and prognosis.
Read the full abstract on PubMed
Practical Takeaways
- •Suspect PHF in horses with acute colitis in endemic areas; use PCR testing of blood and feces for confirmation
- •Treat with tetracyclines and provide comprehensive supportive care including fluid therapy, colloids, NSAIDs, anti-endotoxin medication, and digital cryotherapy
- •Consider infection source related to aquatic insects and trematodes when managing at-risk populations
Key Findings
- •Potomac horse fever is caused by Neorickettsia spp., with N. risticii and N. findlayensis being identified causative agents
- •Horses become infected through ingestion of infected trematodes within aquatic insects
- •Clinical signs include diarrhea, fever, anorexia, lethargy and colic
- •PCR of blood and feces is the diagnostic test of choice, and tetracyclines remain effective treatment