|Description:||This photograph depicts a Phlebotomus papatasi sand fly, which had landed atop the skin surface of the photographer, who’d volunteered himself as host for this specimen’s blood meal. The sand flies are members of the Dipteran family, Psychodidae, and the subfamily Phlebotominae. This specimen had just completed its ingestion of its bloodmeal, which is visible through its distended transparent abdomen. Sand flies such as this P. papatasi, are responsible for the spread of the vector-borne parasitic disease Leishmaniasis, which is caused by the obligate intracellular protozoa of the genus Leishmania.|
Leishmaniasis is transmitted by the bite of infected female phlebotomine sand flies, injecting the infective stage (i.e., promastigotes) from their proboscis during blood meals. Promastigotes that reach the puncture wound are phagocytized by macrophages ,and other types of mononuclear phagocytic cells, and inside these cells, transform into the tissue stage of the parasite (i.e., amastigotes), which multiply by simple division and proceed to infect other mononuclear phagocytic cells. Parasite, host, and other factors affect whether the infection becomes symptomatic and whether cutaneous or visceral leishmaniasis results. Sand flies become infected by ingesting infected cells during blood meals. In sand flies, amastigotes transform into promastigotes, develop in the gut, (in the hindgut for leishmanial organisms in the Viannia subgenus; in the midgut for organisms in the Leishmania subgenus), and migrate to the proboscis. See PHIL 3400 for a diagram of this cycle.