Cutaneous Leishmaniasis Disease Background
Although cutaneous leishmaniasis (CL) is not life-threatening, it can have devastating effects on local communities. Indeed, the disfiguring lesions it causes can lead to affected persons being stigmatized, with consequences such as ostracism, impaired education, and economic loss – all of this in populations with already limited resources. It can become disseminated and produce generalized debilitating disease in immunosuppressed persons (e.g. HIV-affected patients).The exact incidence of cutaneous leishmaniasis is not known, but an estimated 700,000-1,300,000 cases occur every year, most of them affecting children, and only very few receive treatment.
Cutaneous leishmaniasis has a wide distribution, spreading from the Indian subcontinent, across Central and South-Western Asia, to the Mediterranean Basin, the northern half of the African continent, and Central and South America, but 90% of cases are found in Iran, Syria, Saudi Arabia, Afghanistan, Peru and Brazil. In its different forms, cutaneous leishmaniasis is caused by over 15 different species of the protozoan parasite Leishmania, transmitted by infected female sandflies. The reservoir host is either infected humans (anthroponotic CL- ACL, post kala-azar dermal leishmaniasis – PKDL) or mammals (zoonotic – ZCL).
DNDi is focused on developing treatment for cutaneous leishmaniasis caused by L. tropica and L. braziliensis – because of the severity of these diseases and their public health importance.
Anthroponotic CL is caused by L. tropica and is prevalent in Afghanistan, Iran, Iraq, Jordan, Lebanon, Syria, Turkey, and parts of Saudi Arabia and India. ACL tends to heal spontaneously within 1-2 years, but leaves
disfiguring scars. The rate of efficacy with current treatments is lower than 50% in many sites and the disease can lead to recurring cutaneous leishmaniasis, known as leishmaniasis recidivans, which occurs in some cases where small nodules develop around a healed scar; leishmaniasis recidivans is difficult to treat and acts as a reservoir for cutaneous leishmaniasis. Early diagnosis and treatment are essential to reduce the reservoir of infection and control cutaneous leishmaniasis.
Zoonotic CL of the New World (NWCL), prevalent in Central and South America, is caused by two subgenera of the parasite: Leishmania leishmania (e.g., Leishmania mexicana, Leishmania amazonensis)and Leishmania viannia (e.g., Leishmania braziliensis, Leishmania guyanensis). An important and devastating sequel of the disease, particularly associated with L. braziliensis is mucosal leishmaniasis (ML), which can develop in 2-5 % of patients with cutaneous leishmaniasis, sometimes years after recovery. ML is a horrific disease that destroys the mucous membranes of the nose, mouth, and throat and can lead to respiratory tract mucosal invasion, causing numerous respiratory problems, resulting in malnutrition and pneumonia. Mucosal leishmaniasis never heals spontaneously, is very difficult to treat, with secondary bacterial infections common.