Tick-borne diseases

It is well known that ticks carry and transmit a large number of infectious agents. The Ixodes tick and close relatives are no exception. This review examines the diseases and laboratory diagnosis of four such infectious agents: Borrelia burgdorferi, Ehrlichia, Babesia, and Deer tick virus. B. burgdorferi infection can produce a wide spectrum of clinical manifestations making the clinical diagnosis of Lyme disease difficult. Lyme disease diagnostic laboratory tests have not yet demonstrated a clearly superior test, especially in the climate of testing misuse (i.e., tests being performed without regard for an appropriate clinical history). Lyme disease second-tier testing (immunoblotting) has become more standardized in method and in interpretation. Ehrlichiosis is caused by infection with a Gram-negative bacterium of the family Rickettsiaceae and has clinical features characteristic of that group. The laboratory tests for Ehrlichia are still in their infancy. Babesiosis is caused by an intraerythrocytic protozoan parasite of the genus Babesia. The laboratory diagnosis of babesiosis can be made by examination of a blood smear for intraerythrocytic parasites and by detection of antibodies to Babesia in the late acute phase of the disease. Recently, there has been a report of a virus isolated from Ixodes scapularis called deer tick virus. The symptoms of this subtype virus are unknown and laboratory diagnostics are performed by only a few institutions. Fortunately, the prevalence of this virus in ticks is rare.