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Unit Code 81128:
Babesia microti IgG Antibodies, Serum

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Useful For

A serologic test can be used as an adjunct in the diagnosis of

babesiosis or in seroepidemiologic surveys of the prevalence of

the infection in certain populations. Babesiosis is usually diagnosed by

observing the organisms in infected RBCs on Giemsa-stained thin

blood films of smeared peripheral blood.

 

Serology may be useful if the parasitemia is too low to detect or

if the infection has cleared naturally or following treatment.

 

Serology may also be useful in the follow-up of documented cases

of babesiosis or if chronic or persistent infection is suspected.

Clinical Information

Babesiosis is a zoonotic infection caused by the protozoan parasite

Babesia microti. The infection is acquired by contact with Ixodes ticks

carrying the parasite. The deer mouse is the animal reservoir and,

overall, the epidemiology of this infection is much like that of Lyme

disease. Babesiosis is most prevalent in the Northeast, Upper

Midwest, and Pacific Coast of the United States.

 

Infectious forms (sporozoites) are injected during tick bites and

the organism enters the vascular system where it infects red blood

cells (RBCs). In this intraerythrocytic stage it becomes disseminated

throughout the reticuloendothelial system. Asexual reproduction occurs in

RBCs, and daughter cells (merozoites) are formed which are liberated on

rupture (hemolysis) of the RBC.

 

Most cases of babesiosis are probably subclinical or mild, but the

infection can be severe and life threatening, especially in older or asplenic

patients. Fever, fatigue, malaise, headache, and other flu-like symptoms

occur most commonly. In the most severe cases, hemolysis, acute

respiratory distress syndrome, and shock may develop. Patients may

have hepatomegaly and splenomegaly.

Reference Values

<1:64

Interpretation

A positive result of an indirect fluorescent antibody test (titer > or = 1:64)

suggests current or previous infection with Babesia microti. In general,

the higher the titer, the more likely it is that the patient has an active

infection. Patients with documented infections have usually had titers

ranging from 1:320 to 1:2,560.

Cautions

Previous episodes of babesiosis may produce a positive serologic

result.

 

In selected cases, documentation of infection may be attempted by

animal inoculation or polymerase chain reaction (PCR) methods

(#81147 "Babesia microti DNA Detection by Rapid PCR, Blood")

 

Performance characteristics have not been established for the

following specimen characteristics:

- Lipemic

- Hemolyzed

Clinical Reference

Spach DH, Liles WC, Campbell GL, et al:  Tick-borne diseases in the

United States. N Engl J Med 1993;329:936-947

Key