Neorickettsia risticii (previously Ehrlichia risticiii) is a gram-negative intracellular bacterium. Neorickettsia risticii causes potomac horse fever (PHF) and is an acute enterocolitis, producing mild colic, fever, and diarrhea in horses of all ages, and abortion in pregnant mares. The enterocytes infect the small and large intestine resulting in acute colitis, a primary clinical sign of PHF. This disease occurs in spring, summer, and early fall; and is associated with pastures located near creeks or rivers. Exposure to this pathogen is believed to occur by ingestion of aquatic insects that carry N. risticii.1 The incubation period occurs for 10 to 18 days. Horses diagnosed with PHF are not contagious. Initial clinical symptoms are characterized by mild depression, anorexia, and a fever. Within 48 hrs. signs may include severe sepsis, dehydration, and abdominal discomfort. N. risticii can be diagnosed using polymerase chain reaction (PCR), a technique that confirms the presence of a pathogen by identifying nucleic acids. Currently, PCR detection of the bacterium in blood is the only diagnostic method available.2 The Fluxergy N. risticii PCR assay has been designed to target a conserved region of this bacteria and allows for rapid detection of the pathogen within close proximity of the patient.