Translate

Leishmaniadonovani: Pathogenesis, epidermiology and diagnosis


L. donovanidonovani, infection of the classic kala-azar (“black sickness”) or dumdum fever type occurs in many parts of Asia, Africa and Southeast Asia

Important features- the natural habitat of L.donovani in man is the reticuloendothelial system of the viscera, in which the amastigote multiplies by simple binary fission until the host cells are destroyed, whereupon new macrophages are parasitized. In the digestive tract of appropriate insects, the developmental cycle is also simple by longitudinal fission of promastigote forms. The amastigote stage appears as an ovoidal or rounded body, measuring about 2-3μm in length; and the promastigotes are 15-25μm lengths by 1.5-3.5μm breadths.

Pathogenesis

In visceral leishmaniasis, the organs of the reticuloendothelial system (liver, spleen and bone marrow) are the most severely affected organs. Reduced bone marrow activity, coupled with cellular distraction in the spleen, results in anaemia, leukopenia and thrombocytopenia. This leads to secondary infections and a tendency to bleed. The spleen and liver become markedly enlarged, and hypersplenism contributes to the development of anaemia and lymphadenopathy also occurs. Increased production of globulin results in hyperglobulinemia, and reversal of the albumin-to-globulin ratio.

Epidemiology

L. donovanidonovani, infection of the classic kala-azar (“black sickness”) or dumdum fever type occurs in many parts of Asia, Africa and Southeast Asia. Kala-azar occurs in three distinct epidemiologic patterns. In Mediterranean basin (European, Near Eastern, and Africa) and parts of China and Russia, the reservoir hosts are primarily dogs and foxes; in sub-Saharan Africa, rats  and  small carnivores are believed to be the main reservoirs. 

In India and neighboring countries (and Kenya), kala-azar is anthroponosis, i.e. there is no other mammalian reservoir host other than human. The vector is the Phlebotomussand fly. Other variants of L. donovani are also recognized: L. donovaniinfantumwith similar geographical distribution, reservoir host and vector; with L. donovanidonovani. L. donovanichagasi is found in South America, Central America, especially Mexico, and the West Indies. Reservoir hosts are dogs, foxes, and cats, and the vector is the Lutzomiya sand fly.



Clinical features

Symptoms begin with intermittent fever, weakness, and diarrhea; chills and sweating that may resemble malaria symptoms are also common early in the infection. As organisms proliferate and invade cells of the liver and spleen, marked enlargement of the organs, weight loss, anemia, and emaciation occurs. With persistence of the disease, deeply pigmented, granulomatous lesion of skin, referred to as post-kala-azar dermal leishmaniasis, occurs. Untreated visceral leishmaniasis is nearly always fatal as a result of secondary infection.

Immunity

Host cellular and humoral defence mechanisms are stimulated.

Laboratory diagnosis

• Examination of tissue biopsy, spleen aspiration, bone marrow aspiration or lymph node aspiration in properly stained smear (e.g. Giemsa stain).
• The amastigotes appear as intracellular and extra cellular L. donovan (LD) bodies.
• Culture of blood, bone marrow, and other tissue often demonstrates the promastigote stage of the organisms.
• Serologic testing is also available.
Leishmaniadonovani: Pathogenesis, epidermiology and diagnosis Leishmaniadonovani: Pathogenesis, epidermiology and diagnosis Reviewed by gafacom on November 27, 2019 Rating: 5

No comments:

Powered by Blogger.