Leishmaniasis, also spelled leishmaniosis, is a disease caused by protozoan parasites of the genus Leishmania and spread by the bite of certain types of sandflies.[2] The disease can present in three main ways: cutaneous, mucocutaneous, or visceral leishmaniasis.[2] The cutaneous form presents with skin ulcers, while the mucocutaneous form presents with ulcers of the skin, mouth, and nose, and the visceral form starts with skin ulcers and then later presents with fever, low red blood cells, and enlarged spleen and liver.[2][3]

Infections in humans are caused by more than 20 species of Leishmania.[2] Risk factors include poverty, malnutrition, deforestation, and urbanization.[2] All three types can be diagnosed by seeing the parasites under the microscope.[2] Additionally, visceral disease can be diagnosed by blood tests.

Leishmaniasis can be partly prevented by sleeping under nets treated with insecticide.[2] Other measures include spraying insecticides to kill sandflies and treating people with the disease early to prevent further spread.[2] The treatment needed is determined by where the disease is acquired, the species of Leishmania, and the type of infection.[2] Some possible medications used for visceral disease include liposomal amphotericin B,[4] a combination of pentavalent antimonials and paromomycin,[4] and miltefosine.[5] For cutaneous disease, paromomycin, fluconazole, or pentamidine may be effective.[6]

About 12 million people are currently infected[7] in some 98 countries.[3] About 2 million new cases[3] and between 20 and 50 thousand deaths occur each year.[2][8] About 200 million people in Asia, Africa, South and Central America, and southern Europe live in areas where the disease is common.[3][9] The World Health Organization has obtained discounts on some medications to treat the disease.[3] The disease may occur in a number of other animals, including dogs and rodents.[2]

Signs and symptoms
Cutaneous leishmaniasis ulcer on left forearm

The symptoms of leishmaniasis are skin sores which erupt weeks to months after the person is bitten by infected sand flies.

Leishmaniasis may be divided into the following types:[10]

Cutaneous leishmaniasis is the most common form, which causes an open sore at the bite sites, which heals in a few months to a year and half, leaving an unpleasant-looking scar.[2][3] Diffuse cutaneous leishmaniasis produces widespread skin lesions which resemble leprosy, and may not heal on its own.[3]
Mucocutaneous leishmaniasis causes both skin and mucosal ulcers with damage primarily of the nose and mouth.[2][3]
Visceral leishmaniasis or kala-azar (‘black fever’) is the most serious form, and is potentially fatal if untreated.[2] Other consequences, which can occur a few months to years after infection, include fever, damage to the spleen and liver, and anemia.[2]

Leishmaniasis is considered one of the classic causes of a markedly enlarged (and therefore palpable) spleen; the organ, which is not normally felt during examination of the abdomen, may even become larger than the liver in severe cases.