Human ehrlichiosis is a zoonotic infection in humans transmitted by a variety of tick species. The genus Ehrlichiae are characterized by small, rounded gram-negative cocci that invade white blood cells. It is quite similar to the rocky mountain spotted fever, but rash is not seen in patients.

Canine ehrlichiosis is also a zoonotic infection in dogs transmitted by the brown tick. If treated during the acute phase of the disease (weeks one through three after infection by the tick) the survival rates are very good. However, if the illness progresses to the chronic phase then the odds of recovery are greatly reduced.

German shepherd dogs are particularly susceptible to canine ehrlichiosis. During America's involvement in Vietnam many German shepherd dogs were lost to the disease.

The causative organism are Ehrlichia chaffenesis, and E. equii. The incubation period of the disease is one week. Cases are usually seen during summer. For treatment, tetracycline or doxycycline is used.