Leishmaniasis is a parasitic disease caused by several species of genus Leishmania (protozoa) and transmitted by the bite of sand flies. Sand flies are primarily infected by animal reservoir, but humans are also a reservoir for some Leishmania species. Leishmaniasis currently threatens 350 million men, women and children in 88 countries around the world. The leishmaniases are parasitic diseases with a wide range of clinical symptoms:
- Cutaneous leishmaniasis: Involving the skin at the site of a sandfly bite. Cutaneous forms of the disease normally produce skin ulcers on the exposed parts of the body such as the face, arms and legs. The disease can produce a large number of lesions-sometimes upto 200 causing serious disability.
- Visceral Leishmaniasis: Involving liver, spleen and bone marrow. It is also known as Kala-azar and is characterised by irregular bouts of fever, substantial weight loss, hepatomegaly, splenomegaly and anaemia. If left untreated, the fatality rate in developing countries can be as high as 100% within 2 years.
- Mucocutaneous Leishmaniasis: Involving mucous membrane of the mouth and nose after spread from a nearby cutaneous lesion. Lesions can lead to the partial or total destruction of the mucous membranes of the nose, mouth and throat cavities and surrounding tissues.
Different species of leishmania cause different disease;
- Leishmania donovani causes visceral leishmaniasis also called kala-azar. The infection is generalized and the parasite is distributed in the internal organs. The parasite may also cause a variety of skin lesions (dermal leishmaniasis) without any visceral manifestations.
- Leishmania tropica causes oriental sore. The infection is limited to a local lesion of the skin and subcutaneous tissues.
- Leishmania brasiliensis causes espundia. The infection is limited to a local lesion of the skin but may metastasise to other areas of skin and oro-nasal mucosa
Prevention and Control of Visceral Leishmaniasis
Since man is the only reservoir of kala-azar in Nepal, active and passive case detection and treatment of those found to be infected (including PKDL) may be sufficient to abolish the human reservoir and control the disease.
The application of residual insecticides has proved effective in the control of sandflies. DDT is the first choice since the vector of kala-azar P. argentipes is susceptible to DDT. Insecticide spraying should be undertaken in human dwellings, animal shelters and all other resting places up to a height of 6 feet from floor level. Spraying should be preceded and followed by an assessment of susceptibility. Any sign of resistance in vector should lead to an immediate change in insecticide. BHC should be kept as a second line of defence.
Early diagnosis and treatment are essential for both individual patients and for the community. Untreated VL patients act as a reservoir for parasites and therefore contribute to disease transmission in anthroponoticVL areas.
The risk of infection can be reduced through health education and by the use of individual protective measures such as avoiding sleeping on floor, using fine-mesh nets around the bed. Insect repellents for temporary protection and keeping the environment clean.