Leishmaniasis

Abstract

Leishmaniasis constitutes a group of parasitic diseases caused by protozoan flagellated kinetoplastids of the genus Leishmania. The dimorphic parasites infect humans and animals. They are transmitted through the infective bite of the sand fly insect vector, Phlebotomus spp. (Old World, OW) or Lutzomyia (New World, NW). The disease presentations range from self-healing limited cutaneous lesions (cutaneous leishmaniasis, CL) to diffuse cutaneous (DCL) and debilitating mucocutaneous infections (mucocutaneous leishmaniasis, MCL), subclinical viscerotropic dissemination and fatal visceral involvement (visceral leishmaniasis, VL). In VL Leishmania parasites disseminate throughout the reticuloendothelial system and are opportunistic in HIV/AIDS or other conditions of cell-mediated immunosuppression. An insidious complication of VL (syn. Kala azar; Hindi for black fever) is a depigmenting skin condition named as post-kala-azar dermal leishmaniasis (PKDL).

Case Study

A 5-year-old boy presented to the Children’s Hospital in Cairo with intermittent fever reaching up to 40 °C for 25 days that did not respond to usual antipyretics. The mother gave history of having spent their summer holiday 2 months previously in a resort in Agamy area on the West Mediterranean coast of Alexandria. On examination the spleen was enlarged about 10 cm below the coastal region, and the liver was likewise enlarged and tender on palpation. Some neck, axillary and inguinal lymph nodes were palpable. A complete blood picture revealed haemoglobin level of 6.5 g/dl, RBC count of 3.5 mill./cu mm, leucopenia of 2.5 Th./cu mm, neutropenia of segmented neutrophils 18% and thrombocytopenia of 95 Th./cu mm. ESR and C-reactive protein were raised to 60 mm and 125 mg/L, respectively. Liver function tests were raised. Preliminary examination of blood film and thick drop revealed apoptotic monocytes with scattered amastigotes of Leishmania. The condition was diagnosed as infantile VL and successfully treated with liposomal amphotericin (L-AMB) for 5 days, boosted on days 14 and 21.

• 1. Mention the serological tests which can be done to diagnose this condition.

• 2. What are the alternate drugs available for treatment?

• 3. How the disease mentioned here differs from similar disease in Indian subcontinent?

Research Questions

• 1. How to arrive at an updated and simplified taxonomic classification based on phylogenetic relationship of Leishmania species?

• 2. Is the loss of the free flagellum by intracellular amastigotes related to the acidic milieu of the macrophage phagosome?

• 3. How to fast-track the development of an effective vaccine based on genetic diversity and population structure of various Leishmania species?