Potomac Horse Fever (PHF) is an infectious diarrheal disease seen most frequently in the late summer through early fall months.  It is caused by a rickettsial organism, Neorickettsia risticii.  Horses are exposed to Potomac Horse Fever by consumption of infected Cadis flies.

     Initial signs of PHF may include fever, dullness, lethargy, diarrhea, excessive drinking, not eating grain, unenthusiastic grazing or off feed completely.

     Please call if your horse has diarrhea, a temperature above 102 degrees Fahrenheit, or misses more than one meal.

     Diagnosis of PHF is made using blood titer levels which requires two blood tests two to three weeks apart.  A second titer four times greater than the first is considered diagnostic; however, response to treatment is often our best indicator.

     Vaccination against PHF remains controversial.  There are twenty-six known strains of N. risticii that can cause the disease.  The vaccine contains only one strain.  So while we can't prevent the disease we may be able to lessen its severity.