Infective stages of Leishmania in the sandfly vector and some observations on the mechanism of transmission

Abstract

Infective stages of Leishmania (Leishmania) amazonensis, capable of producing amastigote infections in hamster skin, were shown to be present in the experimentally infected sandfly vector Lutzomyia flaviscutellata 15, 25, 40, 49, 70, 96 and 120 hours after the flies had received their infective blood-meal. Similarly, infective stages of Leishmania (L.) chagasi were demonstrated in the experimentally infected vector Lu. longipalpis examined 38, 50, 63, 87, 110, 135, 171 and 221 hours following the infective blood-meal, by the intraperitoneal inoculation of the flagellates into hamsters. The question of whether or not transmission by the bite of the sandfly is dependent on the presence of "metacyclic" promastigotes in the mouthparts of the vector is discussed.

Observations on the development ofLeishmania (L.) chagasiCunha and Chagas in the midgut of the sandfly vectorLutzomyia longipalpis(Lutz and Neiva)

“…The infectivity of midgut contents to hamsters as early as 15-24 hours after the sandfly's infective bloodmeal (Lainson et al, 1987) is presumably due to the small, seemingly unchanged amastigotes (a1). Between 36-43 hours these give rise directly to small promastigotes (a}p), and the infectivity of the gut contents at this time is probably due to both these and any remaining, untransformed a1 amastigotes.…”

“…Methods of infecting the sandflies through a chick membrane on infected hamster spleen, and the subsequent dissection of the infected flies, were as pre viously described (Lainson et al, 1987).…”

“…More recently, discussion of these findings in relation to the mechanism of transmission (Killick-Kendrick, 1986) prompted us to study the infectivity of Leishmania in the sandfly in greater detail, and it was shown (Lainson et al, 1987) examined at 38, 50, 63, 87, 110, 135, 171 and 221 hours following the infective bloodmeal. It was concluded that «... at least some of the flagellates in the sandfly possess the characters of infectivity after a very short sojourn in the insect host -as early as 15 hours », and that « Possibly these parasites have never lost this since the amastigote stage ».…”

The life-cycle ofLeishmaniain the sandfly with special reference to the form infective to the vertebrate host

“…longipalpis (Lainson et al, 1987). Divi ding amastigotes were seen in stained smears of the infected midguts of sandflies which had fed through a membrane on suspensions of amastigotes 24, 36 and 43 h before dis section.…”

“…flaviscutellata and L. i. cha gasi in Lu. longipalpis, Lainson et al (1987) showed that at least some parasites were infective to hamsters 15 h after an infective bloodmeal. In studies on the morphology of L. i. chagasi in Lu.…”