Leishmaniasis is a chronic parasitic disease, which exists in two forms: visceral leishmaniasis (also known as kala-azar), which affects the internal organs such as the liver and spleen, and cutaneous leishmaniasis, which affects the skin. The infectious agents are protozoa (single-celled organisms, figure below).
The major species of Leishmania protozoa are:
- Leishmania donovani, which causes visceral leishmaniasis
- Leishmania aethiopica, Leishmania major and Leishmania tropica, all of which cause cutaneous leishmaniasis.
Leishmaniasis is pronounced 'lye-sh-man-eye-assis'. Visceral is pronounced 'viss-urr-al' and cutaneous is pronounced 'kute-ay-nee-ous'.
Around 12 million people in 88 countries around the world are currently thought to be infected with Leishmania parasites and the WHO estimates that one to two million new cases occur each year. The vectors (and intermediate hosts) for these parasites are sandflies. The lifecycle will be described later in this section.