37.2.2  Mode of transmission of leishmaniasis

Leishmaniasis is transmitted through the bite of female phlebotomine sandflies (Figure 37.7), which bite humans and some animals, and take blood meals to feed the development of their eggs. Phlebotomine means ‘blood-sucking’ and is pronounced ‘fleb-otto-meen’. There are about 30 species of sandflies that can transmit Leishmania parasites to humans found throughout the tropical and temperate regions of the world. The females lay their eggs in many locations, including the burrows of rodents, old tree bark, cracks in buildings and rubbish heaps – anywhere that is warm and humid enough for their eggs to develop into flies.

Figure 37.7  A female phlebotomine sandfly taking a blood meal from a person’s arm. Note the human blood in its transparent abdomen. (Photo: CDC Image Library, image 10276/James Gathany)

When sandflies take blood meals from an infected person, they also become infected with the protozoa that cause leishmaniasis. The protozoa develop inside the sandfly and are passed on when the sandfly takes a blood meal from a healthy person. The Leishmania protozoa multiply inside the white blood cells of the healthy person and cause disease (Figure 37.8).

Figure 37.8  Transmission of Leishmania parasites from a sick person to a healthy person by a sandfly. The enlarged abdomen of the sick person on the left indicates visceral leishmaniasis affecting the internal organs.