Neglected Tropical Disease

Leishmaniasis includes two major diseases, cutaneous leishmaniasis and visceral leishmaniasis, caused by more than 20 different leishmanial species.

Cutaneous leishmaniasis, the most common form of the disease, causes skin ulcers. Visceral leishmaniasis causes a severe systemic disease that is usually fatal without treatment. Mucocutaneous leishmaniasis is a rare but severe form affecting the nasal and oral mucosa.

Leishmaniasis is transmitted by the bite of small insects called sand flies. Many leishmanial species infect animals as well as humans. The distribution is world-wide, but 90% of visceral leishmaniasis cases occur in India, Bangladesh, Nepal, Sudan, Ethiopia and Brazil, while 90% of cutaneous leishmaniasis cases occur in Afghanistan, Algeria, Iran, Saudi Arabia, Syria, Brazil, Colombia, Peru and Bolivia.

Lymphatic filariasis, commonly known as elephantiasis, s caused by infection with nematodes (roundworms) of the family Filariodidea. Adult worms lodge in the lymphatic system and disrupt the immune system. They live for 6-8 years and, during their life time, produce millions of microfilariae (small larvae) that circulate in the blood. Lymphatic filariasis is transmitted by different types of mosquitoes. The majority of infections are asymptomatic, showing no external signs of infection.Acute episodes of local inflammation involving skin, lymph nodes and lymphatic vessels often accompany the chronic lymphoedema or elephantiasis.

Dozens of different sand fly vectors, adapted to the different ecological settings where leishmaniasis occurs, are known to transmit some form of leishmaniasis. Leishmaniasis, especially the visceral form, can also be transmitted by blood transfusion or sharing of contaminated needles. Congenital transmission has been reported, but appears to be rare.

In sylvatic cycles, such as those in New World rain forests and the deserts of Central Asia, animal reservoir hosts can maintain transmission indefinitely without human disease. Sporadic or epidemic leishmaniasis occurs when humans enter the sylvatic habitat for economic or military purposes, or when human habitation encroaches on the sylvatic setting. In domestic cycles, humans or dogs form the predominant or sole infection reservoir. In the Mediterranean basin and parts of Latin America, visceral leishmaniasis transmission is zoonotic (dog – sand fly – human). The area that account for the largest number of human cases, for example, visceral leishmaniasis in South Asia and cutaneous leishmaniasis in Afghanistan, usually reflect anthroponotic (human - sand fly - human) transmission.

21 of the 30 species in the protozoan genus, Leishmania, that infect other mammals

90% of visceral leishmaniasis cases occur in parts of India, Bangladesh, Nepal, Sudan, Ethiopia and Brazil

90% of cutaneous leishmaniasis cases occur in parts of Afghanistan, Algeria, Iran, Saudi Arabia, Syria, Brazil, Colombia, Peru and Bolivia

by the bite of infected female phlebotomine sandflies

1. The sandflies inject the infective stage (i.e., promastigotes) from their proboscis during blood meals. 2.Promastigotes that reach the puncture wound are phagocytized by macrophages and other types of mononuclear phagocytic cells. 3.Progmastigotes transform in these cells into the tissue stage of the parasite (i.e., amastigotes), which 4. multiply by simple division and proceed to infect other mononuclear phagocytic cells. Parasite, host, and other factors affect whether the infection becomes symptomatic and whether cutaneous or visceral leishmaniasis results. 5. Sandflies become infected by ingesting infected cells during blood meals. In sandflies, 6.amastigotes transform into promastigotes, 7.develop in the gut (in the hindgut for leishmanial organisms in the Viannia subgenus; in the midgut for organisms in the Leishmania subgenus), and 8.migrate to the proboscis.

a febrile illness with weight loss, enlargement of the spleen and liver, and decreases in the production of blood cells that can lead to anemia, bleeding and infections with other microorganisms. Without treatment, this form of the disease is nearly always fatal.

is the more common form and appears in 1 or more painless ulcers

a rare form of the disease that can occur months or years after the healing of a CL ulcer. This form of the disease can affect the nasal septum, palate and other parts of the nasopharynx.

requires biopsies of the ulcer, the blood or bone marrow, or the affected area. and then growing the tissue in culture to look for leishmania species. May take a while.

L. major and L. tropica in the Old World

L. braziliensis, L. mexicana, and related species in the New World