When the infected cells rupture, the infection spreads to other organs. Body temperature is an important factor that determines the localization of leishmanial lesions. Species causing cutaneous leishmaniasis cannot grow at core body temperature, while species causing visceral leishmaniasis are able to grow at these temperatures. In cutaneous leishmaniasis, the hallmark of the disease is skin lesions, which can spontaneously heal in 2-10 months. In mucocutaneous leishmaniasis, mucosal ulcerations usually develop by metastasis rather than by local spread.
Secondary infection plays a prominent role in the size and persistence of ulcers.
Their progression is slow and steady. Typically, visceral leishmaniasis incubates for weeks to months. The disease can be subacute, acute or chronic. It is found in the eastern half of Africa, from the Sahara in the North to the Equator. It generally affects older children and young adults.