Development and infectivity of Trypanosoma phaleri in leech and fish hosts

Abstract

Trypanosoma phaleri underwent cyclopropagative development in the gut of the leech Desserobdella phalera. Dividing sphaeromastigotes and epimastigotes preceded nondividing, elongate, slender trypomastigotes. The latter forms migrated from the crop to the proboscis sheath, shortened, and acquired infectivity. Metatrypanosomes from the proboscis sheath but not those from the crop were infective. The flagellum of short metatrypanosomes penetrated the cuticular lining of the proboscis sheath. Proboscis-sheath infections were first detected 9 days after an infective blood meal in 2 of 10 leeches incubated at 13 °C and after 2 days in 1 of 10 leeches incubated at 20 °C. In the former group, 3 of 10 leeches had proboscis-sheath infections after 11 days whereas in the latter group, 9 of 10 leeches had proboscis-sheath infections after 5 days. Metatrypanosomes did not reinvade the proboscis sheath when infected leeches fed on uninfected Amia calva but did so if the subsequent blood meal was infective. Developmental stages were not detected in 49 leeches that fed on A. calva with infections of 24 and 48 h but were detected in 4 of 27 leeches that fed on A. calva with 72-h infections.