In this article we will discuss about:- 1. Morphology and Lifecycle of Leishmania Tropica 2. Pathogenicity of Leishmania Tropica 3. Treatment of Disease Caused.
Morphology and Lifecycle of Leishmania Tropica:
The morphology and life cycle of Leishmania Tropica resemble those of L. donovani. The amastigote are present in the skin, within large mononuclear cells, in neutrophils, inside capillary endothelial cells and also free in the tissues. They are ingested by sandflies, feeding near the skin lesions.
In the midgut of the sand-fly, the amastigotes develop into promastigotes which replicate profusely. These are, in turn, transmitted to the skin of persons bitten by the sandflies.
In the skin, the promastigotes are phagocytosed by the mononuclear cells, in which they become amastigotes and multiply. However, they remain confined to the skin, without being transported to the internal organs as in the case in visceral leishmaniasis.
Pathogenicity of Leishmania Tropica:
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Mode of transmission and incubation period:
Though the common mode of infection is through sandflies, infection may also sometimes occur by direct contact. Infection may be transmitted from man to man or animal to man by direct inoculation of amastigotes. Infection may also occur by autoinoculation.
Sometimes, sand-fly may act as mechanical vector by transmitting the amastigotes from a sore of a patient into the bite wound on another person. The incubation period lasts from a few days to several months.
Pathogenesis:
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The first symptom of oriental sore is a small red papule at the site of fly-bite. This may disappear in a few weeks, but usually it develops a thin crust that hides a spreading ulcer underneath. In in-complicated cases the ulcer may heal within two months leaving a depressed, impigmented scar.
It is common, however, for secondary infection to occur, including jaws (a disfiguring disease caused by a spirochaete) and myosis (infection with fly maggots). The lesion remains dry, and persists for month before ulcerating and has numerous amastigotes within it.
Treatment of Disease Caused by Leishmania Tropica:
Most cutaneous lesions heal spontaneously. Pentavalent antimonial are the drugs of choice for treatment. Metronidazole, rifampicin and local application of heat also may give good results.