Potomac horse fever
noun
Po·to·mac horse fever
| \ pə-ˈtō-mək-
, -mik-
\
, -mik-
\
Medical 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