HUMAN SERUM RESISTANT PROMASTIGOTES OF LEISHMANIA-INFANTUM IN THE MIDGUT OF PHLEBOTOMUS-PERNICIOSUS

Promastigotes of Leishmania infantum develop from early-stage normal human serum (nHS) sensitive forms to a partially nHS resistant stage in the midgut of Phlebotomus perniciosus. This development begins about day 7 after the sandfly has taken its initial infective bloodmeal. The onset of partial nHS-resistance occurs when mass proliferation of midgut promastigotes is already completed and the parasites have begun to differentiate into small, highly motile cells. In this parasite/vector interrelationship, the stomodeal valve seems to be a barrier which limits the development of L. infantum in P. perniciosus to the midgut.