Leishmania: a Parasite on the Move

Abstract

During the past decade, there has been an increase in numbers of new cases, spread of the disease into new regions, and even appearance of new clinical syndromes. This resurgence of leishmaniasis reflects the remarkable adaptability of the Leishmania parasite to changing conditions, such as those resulting from economic development, human modification of the environment, and population movements. In visceral leishmaniasis, or kala-azar, there is infection of reticuloendothelial cells throughout the body and particularly in the liver, spleen, bone marrow, and lymphoid tissue. In cutaneous leishmaniasis, parasite replication is confined primarily to the skin. Treatment is required for persons with clinically apparent visceral leishmaniasis, mucocutaneous leishmaniasis, and cases of cutaneous leishmaniasis in which spontaneous healing is slow, lesions involve the face, or infection is due to species that can cause mucocutaneous leishmaniasis or diffuse cutaneous leishmaniasis. The gold standard treatment is pentavalent antimony given intravenously or intramuscularly at a dose of 20 mg/kg/day for a minimum of 20 days. Visceral leishmaniasis in HIV-infected persons is associated with higher levels of parasitemia than is seen in non-HIV-infected persons, and sand flies readily acquire parasites from coinfected persons. Measures to control the spread of visceral leishmaniasis in Teresina have focused on identifying and killing infected dogs, and application of insecticide in the neighborhoods surrounding new cases of frank kala-azar. High among the priorities for research on leishmaniasis is the development of new methods for predicting the occurrence of outbreaks and establishment of new foci of transmission.