Potomac horse fever

Po·to·mac horse fever

noun \pə-ˈtō-mək-, -mik-\

Definition of POTOMAC HORSE FEVER

: an often fatal disease of horses that is marked by fever, loss of appetite, diarrhea, and laminitis, that is caused by a bacterium of the genus Ehrlichia (E. risticii), and that was discovered in the region of the Potomac River in Maryland but is much more widespread—called also Potomac fever