ABSTRACT Potomac Horse Fever is a seasonal disease and acute enterotyphlocolitis of horses caused by infection with monocytotropic rickettsia, Neorickettsia risticii, formerly called Ehrlichia risticii. In simple terms, we can say that colitis or diarrhoea is caused by Neorickettsia risticii. Geographically restricted to a limited area in North America. Neorickettsia risticii is a gramme-negative coccus. Now we will discuss PHF…