Single-celled parasites called leishmania cause leishmaniasis. Leishmania have existed for hundreds of millions of years. The parasites have a life cycle that needs sand flies and mammals. They live within rodents in the tropics, subtropics, and southern Europe.
Image of leishmania through a microscope
A sand fly filled with blood on human skin
Sand fly eggs hatch a few weeks after being laid. Once hatched, the larvae search for enough food to support them through their journeys as pupae and into adulthood. Once adults, only female sand flies will feast on blood, a vital resource in the creation of eggs. If the sand flies feed on the blood of an animal infected with leishmania, they become infected. These parasites wait for the fly’s next meal when they are released and able to make a new home in a mammal.
Moche ceramic vessel depicting someone with mucocutaneous leishmaniasis
Unknown Moche artist
Peru, 450-550 CE
A man with cutaneous leishmaniasis Credit: Library of Congress
Inside a human, leishmania invade our white blood cells and continue to reproduce. Sometimes nothing happens when we are infected, other times the infection can lead to three forms of leishmaniasis: visceral, cutaneous, and mucocutaneous.
Visceral leishmaniosis is fatal if left untreated. It causes fever, weight loss, spleen and liver enlargement, and anemia.
Cutaneous leishmaniasis causes skin lesions on exposed parts of the body that leave life-long scars and can lead to stigma and discrimination.
Mucocutaneous leishmaniosis leads to partial or total destruction of mucous membranes in the nose, mouth, and throat.
Several factors support leishmaniasis. Socioeconomic situations that keep people in poor housing and sanitary conditions create more sand fly breeding sites and access to humans. Malnutrition may increase the likelihood that an infection develops into a full-blown disease. Tourism, occupation, and migration bring non-immune people, willingly or unwillingly, into areas with existing cycles of leishmania.
Fluctuations in temperature and drought, famine, and flood associated with climate change are allowing sand flies and leishmania to move into new areas. These conditions also move and displace people into these same areas.
Map of countries with case(s) of Leishmaniasis
Leishmaniasis is a treatable and curable disease. But, a strong immune system is needed because medicines are unable to fully get rid of the parasites. Many people cannot access treatment because it is too expensive or locally unavailable.
It is estimated that over 1 million people are infected with leishmania and around 60,000 people die from the disease each year.