Clinical and Experimental Advances in Treatment of Visceral Leishmaniasis

Visceral leishmaniaisis (kala-azar) is a disseminated protozoal infection, transmitted by sandfly bite, in which macrophages of the liver, spleen, and bone marrow are preferentially parasitized and support intracellular replication. Most human infections caused by visceralizing strains of Leishmania are probably subclinical (13, 101, 139), attesting to innate resistance or, more likely, to T (Th1)-cell-dependent immune responses which induce acquired resistance (33, 39, 79, 101, 102). While treatment is not given for subclinical infection, remote recrudescence still remains a possibility, especially if the host becomes T-cell deficient (62, 66, 76, 123). In contrast, if the initial Th1-cell-associated immune response fails to develop or its effector mechanisms are disabled or not properly maintained (122, 123), recently acquired (or reactivated) kala-azar evolves to full expression as a subacute or chronic illness for which treatment is required.