New perspectives on a subclinical form of visceral leishmaniasis.

During an epidemiological study of visceral leishmaniasis in an endemic region of Brazil, new perspectives emerged on a subclinical form of the disease. A group of 86 children with antibody to Leishmania were identified. None of these children had a history of leishmaniasis. The children were segregated into four groups: One group remained asymptomatic (n = 20), whereas another developed classic kala-azar within weeks of the index serology (n = 15). The remaining 51 patients initially had subclinical disease; 13 (25%) of these patients progressed to classic kala-azar (mean, five months). The others (75%) resolved their illness after a prolonged period (mean, 35 months). The initial illness in the subclinical group was characterized by hepatomegaly, frequent splenomegaly, intermittent cough, diarrhea, and low-grade fever. Malaise and poor weight gain were common. Giemsa-stained smears and cultures of bone marrow aspirates were usually negative for Leishmania in the absence of symptoms of classic kala-azar.