Review maps broader global footprint for Potomac horse fever agent

A new systematic review in Veterinary Research Communications pulls together the scattered global literature on Neorickettsia risticii, the main cause of Potomac horse fever, and argues that the organism’s distribution is broader, and more complex, than many clinicians may assume. The review lands alongside a companion overview in Veterinary Microbiology that frames equine neorickettsiosis as a disease tied to trematode life cycles, aquatic insects, and regional ecology, not just a narrow set of endemic pockets in North America. Current guidance from the American Association of Equine Practitioners also reflects that broader picture, noting that Potomac horse fever is caused by N. risticii and N. findlayensis, and that recognized clinical disease is established in multiple regions of the U.S., Canada, and parts of South America. (deepdyve.com)

Why it matters: For veterinary professionals, the main takeaway is that geography alone may be a weak rule-out. Potomac horse fever remains non-contagious, seasonal, and environmentally linked, but the evidence base now points to a wider international footprint, including reports from South America and references to detections beyond the traditional U.S. endemic narrative. AAEP says cases usually occur in summer and fall, and clinical signs can include high fever, diarrhea, colic, laminitis, edema, and abortion, which means delayed recognition still carries meaningful risk for equine patients. (aaep.org)

What to watch: Expect more discussion around surveillance, species-level diagnostics for Neorickettsia, and whether emerging distribution data should change regional testing and vaccination conversations. (sciencedirect.com)