Leishmaniasis is a parasitic infection which is endemic to many developing nations around the world. There are several forms of leishmaniasis disease, all of which require medical treatment with antiparasitic drugs. Travelers in developing nations are often encouraged to take steps to avoid leishmaniasis infections, especially since the parasitic protozoans which cause the infection are growing steadily more resistant to the antiparasitic drugs most commonly used to treat leishmaniasis.
Several different protozoans can cause leishmaniasis disease, but all of them are in the genus Leishmania. These very simple organisms generally live in animals, and they are picked up by sand flies when those flies feed on animal populations. When the sand flies bite humans, the humans in turn are infected with the protozoans. Most cases of leishmaniasis disease are zoonotic, transmitted from animals to people, although the disease can also be passed from person to person. The best way to avoid leishmaniasis disease is to avoid contact with sand flies, by using screens and insecticides and avoiding the outdoors when the flies are most active, at dawn and dusk.
Once the parasite enters the body, the immune system tries to fight it off, recognizing it as a foreign invader. Macrophages are sent to eat the parasite so that it cannot harm the body, but the leishmaniasis parasites instead turn the macrophages to their advantage, swelling the specialized immune system cells and causing them to burst, thereby spreading the infection further in the body. Without treatment, leishmaniasis disease will run rampant in the body, causing extreme pain and sometimes death.
There are two main forms of leishmaniasis. Cutaneous leishmaniasis causes lesions to appear on the skin, classically with raised edges and depressed craters. The lesions may or may not be painful, depending on the case, but they are typically red, scabby, and very distinctive. Visceral leishmaniasis disease attacks the internal organs of the body, and it is fatal without treatment.
In developing nations, access to drugs and treatments for leishmaniasis is very limited, due to expensive. Visceral leishmaniasis is a major killer of people in many nations throughout Southeast Asia and Africa, because the drugs are expensive or unavailable. Some organizations have attempted to develop effective, low-cost leishmaniasis drugs, but many have been hampered by a lack of interest in developing such drugs on the part of drug companies, as the pharmaceutical industry would prefer to invest in research with a high profit margin.