Ehrlichia ruminantium (formerly Cowdria ruminantium) is an obligately intracellular tick-borne parasite that causes a cowdriosis, an acute and fatal infection of sheep, goats, and cattle. Unlike Anaplasma marginale, E. ruminantium infects nucleated cells, including vascular endothelial cells, monocytes, and neutrophils. Mortality can range from 20-90% depending on a number of factors, but infected animals develop fever, anorexia, circulatory and respiratory difficulties, and in some cases neurological symptoms. Recovered animals become resistant to re-infection to similar strains but maintain a persistent infection and serve as a reservoir for tick transmission.