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The Parasite: Leishmaiasis is found in 88 countries across Asia, Africa, the Middle East, Southern Europe and parts of North, Central and South America. It is caused by the single-celled Leishmania parasite, which develops at the site of a sand fly bite — the sand fly being the insect vector for the parasite. Its life cycle begins when an infected female sand fly — which became infected by biting an infected animal or person — transmits the parasite to a new host.
Sand flies can be tricky to avoid. These tiny, hairy flies are able to pass through most mosquito nets; they do not make any noise when they fly; and their bites are sometimes unnoticeable. Once transmitted to a human host, the Leishmania parasite invades the white blood cells and replicates intracellularly, then moves onto attack the skin cells. When a sand fly bites an infected human, the cycle begins anew.
The Infection: People who are infected with cutaneous leishmaniasis will develop one or more raised red sores or lesions on their skin. These sores can change in size and appearance over time. They can even heal and then reappear in another location. The sores can sometimes appear crater-like, with a raised edge and an ulcer in the center. When ulcerous, the sores can become secondarily infected by bacteria. They can be very painful and are sometimes accompanied by swollen glands near the site of the sores.
Treatment: The skin sores caused by cutaneous leishmaniasis will usually heal without treatment, but this can take months or years. The sores can also leave unsightly scars. Moreover, the infection can sometimes spread from the skin to the nose or mouth and develop into mucosal leishmaniasis. An antimonial agent, such as sodium stibogluconate, is sometimes used to treat the sores. Occasionally they are also surgically removed.
Prevention: There is currently no vaccine to prevent leishmaniasis, although vaccine development is underway. Currently the best way to prevent infection is to prevent sand fly bites, particularly when traveling to parts of the world known for having a high incidence of the infection. In order to do this, individuals should avoid outdoor activities from dusk to dawn, when sand flies are most active. If outdoors, they should minimize the amount of exposed skin and apply insect repellent to uncovered parts of the body. It is also wise to spray living and sleeping areas with insecticide and to use a bed net that has been soaked in insecticide. The same treatment can be given to screens, curtains, sheets and clothing.
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Featured in Outbreak!, Episode 2 of MONSTERS INSIDE ME
These parasites work on a grand scale, infecting and killing in mass numbers. Highlighting angiostrongyliasis, caused by rat lungworm; cryptosporidiosis, caused by Cryptosporidium hominis; and cutaneous leishmaniasis.
 See how cutaneous leishmaniasis affects the body.
Check out the Leishmania parasite in action.
Visit the Monsters Inside Me video gallery.
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