Leishmania donovani and Leishmania infantum/Leishmania chagasi are responsible for most of the cases of visceral leishmaniasis
In an endemic area, the constellation of prolonged fever, progressive weight loss, weakness, pronounced splenomegaly, hepatomegaly, anemia, leukopenia, and hypergammaglobulinemia is highly suggestive of visceral leishmaniasis. The diagnosis is more difficult in persons in whom fever or splenomegaly are absent; in travelers who develop symptoms after leaving endemic areas; and in those with concurrent AIDS who present with atypical manifestations.
The diagnosis can be confirmed by demonstrating amastigotes in tissue or isolating promastigotes in culture. Splenic aspiration for Wright-Giemsa stained smears and for culture is the most sensitive method for parasite identification.
Bone marrow aspiration is safer, but less sensitive. Amastigotes are seen in approximately two thirds of patients. Liver biopsy is less likely to yield the diagnosis than is splenic puncture or bone marrow biopsy and carries the risk of hemorrhage. Lymph node aspiration or biopsy may be diagnostic when enlarged nodes are present.
Antileishmanial antibodies are typically present in high titer in immunocompetent patients with visceral leishmaniasis. Enzyme-linked immunosorbent assay (ELISA) and dipstick tests using L. infantum/L. chagasi recombinant k39, a kinesin-like antigen, have good sensitivity and specificity for the diagnosis of visceral leishmaniasis in immunocompetent persons.
The leishmanin (Montenegro) skin test is negative in patients with active visceral leishmaniasis. It becomes positive in the majority of those in whom infection spontaneously resolves and in patients who have undergone successful chemotherapy.
References:
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Herwaldt BL. Leishmaniasis. Lancet. 1999 Oct 2;354(9185):1191-9. [Medline]
Evans TG. Leishmaniasis. Infect Dis Clin North Am. 1993 Sep;7(3):527-46. [Medline]
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