Scanning electron microscopy of Leishmania major in Phlebotomus papatasi.

The morphology of Leishmania major parasites and their interactions with various regions of the alimentary canal of Phlebotomus papatasi were studied by scanning electron microscopy. Parasites were observed to undergo development initiated with the ingestion of amastigotes and culminating in a characteristic distribution of four distinct morphological forms in various parts of the alimentary canal: namely, large numbers of elongate nectomonads in the abdominal mid-gut, haptomonad forms attached to the cuticle of the stomodeal valve, small spherical forms attached to the esophagus and masses of short promastigotes, believed to be the infective forms, lying free in the anterior thoracic mid-gut and the esophagus.