Lifecycle

from:Parasitic Diseases, 1982. Katz, Despommier, Gwadz, Springer-Verlag. New York.

		Leishmaniasis enters the mammalian host during the blood meal of an infected Phlebotomid sandfly. The parasite enters in the promastigote form and is quickly taken up by macrophages in the mammalian innate immune response.
by: R.L. Jacobson, 1996. http://medstat.med.utah.edu/parasitology/lbrazim.html

Within the macrophage, the promastigote loses its flagella and turns into the amastigote form. Here the parasite employs a variety of strategies to evade the destructive nature of the macrophage.

by:http://cal.vet.upenn.edu/dxendopar/parasitepages/protozoa/leishmania.html

		The parasite grows within the phagolysosome until the macrophage is eventually killed, at which point the amastigotes spill out and infect other macrophages. At this point, the disease can be diagnosed with a blood smear.
by:http://cal.vet.upenn.edu/dxendopar/parasitepages/protozoa/leishmania.html

When another sandfly takes a blood meal, it acquires the infection by ingesting infected macrophages. Once inside the fly's gut, the amastigotes transform back into the promastigote form and attach themselves to the epithelial lining of the gut. In the fly's midgut, the parasite multiplies asexually.

It has been suggested that the quantity of promastigotes in the sandfly's midgut becomes so large that they clog the proboscis. This forces the fly to regurgitate to free the blockage and facilitates the parasite's entry into its new mammalian host.

However, more recent research indicates that the promastigotes secrete a chitinase that damages the fly's cardiac valve. This also increases the amount of regurgitation by hindering the one-way valve mechanism of the valve. Research also suggests that the chininase may allow the parasite to penetrate the peritrophic membrane of the fly and remain in the fly after excretion of the residual blood meal.
 
 

References:
Lee MB, Gilbert HM. Current Approaches to Leishmaniasis. Infect Med 1999;16(1):34,37-45. http://www.medscape.com/SCP/IIM/1999/v16.n01/m3148.lee/pnt-m3148.lee.html

Ohio State. Leishmania spp. http://www.biosci.ohio-state.edu/~parasite/leishmania.html

The Special Programme for Research and Training in Tropical Diseases. Leishmaniasis. http://www.who.int/tdr/diseases/leish/default.htm

University of Pennsylvania Veterinary School. Leishmaniasis. http://cal.vet.upenn.edu/dxendopar/parasitepages/protozoa/leishmania.html

University of Utah. Parasitology http://medstat.med.utah.edu/parasitology/lbrazim.html

WHO. Leishmaniasis. Communicable Disease Surveillance and Response. http://www.who.int/emc/diseases/leish/leisgeo.html