Leishmaniasis is a common parasitic disease that is endemic to most tropical areas, particularly in the Old World. The parasite is rarely transmitted from person to person and usually requires that a person be bitten by an infected sandfly, which is the most common vector of the disease. Recent fossil evidence has shown that the parasite that causes the disease has existed at least since the time of the dinosaurs as it was found in a sandfly trapped in amber.
The disease has two common forms:
- Cutaneous leishmaniasis, which is characterized by one or more large sores on the skin. It results when the parasite is generally limited to the skin's surface.
- Visceral leishmaniasis, which is characterized by multiple organ failure. It results when the parasite enters the bloodstream.
Among parasitic diseases, only malaria kills more people each year than leishmaniasis. About 500,000 people a year develop the disease, and 60,000 die from it.
Leishmaniasis is difficult and dangerous to treat, but can usually be treated successfully. Antimony, otherwise a toxin to humans, is known to be effective against the parasite, but the reasons for this are unknown. However, some cases resolve spontaneously without treatment.