Observations on the development of Leishmania (L.) chagasi Cunha and Chagas in the midgut of the sandfly vector Lutzomyia longipalpis (Lutz and Neiva).

Previous observations have shown that forms of Leishmania, infective to hamsters, are present in the midgut of experimentally infected sandflies from 15-221 hours after the infective bloodmeal. In a continuation of these studies, stained smears of the midgut contents of Lutzomyia longipalpis infected with Leishmania (L.) chagasi, made at intervals between 15-120 hours, revealed two lines of parasite development. One of these is the direct transformation of small, non-dividing amastigotes into very small promastigotes, which are considered to represent the "infective" or "metacyclic" flagellates involved in subsequent transmission of the parasite. The other stems from enlarged, highly vacuolated amastigotes which undergo at least two divisions before giving rise to large, elongate and non-dividing promastigotes. These are thought to represent the non-infective forms of the parasite seen in in vitro cultures, and their function remains speculative.