Ehrlichia canis: a tick-borne rickettsial-like infection in humans living in the southeastern United States.

During the past two years, sporadic cases of a rickettsial-like illness were reported in humans living in the Southeastern United States. The illness was serologically similar to Ehrlichia canis infections in dogs. It resembled spotless Rocky Mountain Spotted Fever but was differentiated from this infection serologically with acute and convalescent sera showing increasing titers to Ehrlichia canis. E. canis infection should be suspected in patients with fever, headache, malaise, myalgia, gastrointestinal symptoms, relative bradycardia, leukopenia, thrombocytopenia, and a recent exposure to either dogs or ticks. Although recovery has been observed in humans without treatment, prompt therapy with tetracycline is advised before obtaining results of serologic studies because an immunologically similar illness in untreated dogs has been lethal.