Leishmaniasis

Lore & Background

Leishmaniasis is caused by more than 20 species of Leishmania, with visceral disease usually caused by L. donovani, L. infantum, or L. chagasi, while cutaneous forms involve over 15 species. The parasites are transmitted when sandflies inject metacyclic promastigotes during blood meals; these are phagocytized by macrophages and transform into amastigotes, which multiply and affect different tissues depending on the species. The genomes of L. major, L. infantum, and L. braziliensis have been sequenced, revealing that protein-coding genes are organized as large polycistronic units and that RNA polymerase II transcribes long polycistronic messages without defined promoters.

Reader's Guide

Leishmaniasis remains a significant public health burden, particularly in impoverished regions where risk factors such as malnutrition, deforestation, and urbanization are prevalent. The disease can be partly prevented by insecticide-treated nets, spraying insecticides, and early treatment. Diagnosis involves microscopy to visualize amastigotes, with PCR tests offering specific and sensitive detection. Treatment depends on the geographic origin, species, and type of infection; for cutaneous disease, paromomycin, fluconazole, or pentamidine may be effective. Recent research explores combination therapies, nanotechnology-based drugs, and immunotherapy. The World Health Organization has obtained discounts on some medications, and the disease also occurs in other animals, including dogs and rodents.

Did You Know?

• Visceral leishmaniasis, also called kala-azar, is generally fatal if untreated.
• Sandflies become infected when they ingest macrophages containing amastigotes during blood meals on infected hosts.
• The genomes of three Leishmania species (L. major, L. infantum, and L. braziliensis) have been sequenced.
• Non-human animals such as dogs, rodents, and even gorillas can be infected with human-infecting Leishmania species.