Detection of amastigote-like forms in the valve of Phlebotomus papatasi infected with Leishmania major

Abstract

A massive and homogeneous amount of amastigote-like forms was detected in the stomodeal valve (SV) and the thoracic mid-gut (TMG) of Leishmania major-infected Phlebotomus papatasi, which received a second blood meal 13 to 21 days post-infection on healthy anaesthetized hamsters. After re-feeding, the infected sand flies were dissected out to examine the morphology of the parasite in SV, TMG and the abdominal mid-gut (AMG) Key words: Phlebotomus papatasi -Leishmania major -amastigote-like forms -transmissionParasites of the genus Leishmania exhibit, during their life cycle, two well-known forms. The flagellated and mobile promastigote form, which multiplies in the gut of phlebotomine sand fly vectors, and the intracellular nonmotile amastigote form normally found within macrophage phagolysosomes of the vertebrate host (KillickKendrick 1990). The sand fly gut is an environment specialized for blood digestion as well as the location where Leishmania-parasites replicate and develop into the infective metacyclic forms that invade the vertebrate host (Tang et al. 1998). Thus far, the Leishmania metacyclic form has been described as a parasite possessing a short body, and a very long flagellum which is found in the foregut including the proboscis of infected sand flies. The metacyclic form is also complement resistant and able to transform into the amastigote form upon infecting the vertebrate host (Killick-Kendrick 1990 a blood meal has been digested. These findings may help interpretation concerning morphological changes in the Leishmania-parasite population in experimentally infected sand flies. In the present paper we report the detection of amastigote-like forms in the stomodeal valve (SV) and TMG of colonized Phlebotomus papatasi which received a second blood meal 13 to 21 days after an experimental infection with Leishmania major. MATERIALS AND METHODSSixty eight specimens of Ph. papatasi from a laboratory colony were experimentally infected with a washed suspension of L. major amastigotes prepared from infected hamster skin tissue. The sand flies were permitted to feed on the suspension through a hamster cheek-pouch attached to a glass feeder warmed by a circulating water bath (Bastien 1990). The suspension was previously diluted with inactivated rabbit blood to give an estimated 3.5 x 10 5 viable amastigotes per 1 ml. Each fly with a full blood meal was estimated to have ingested approximately 100 parasites. Fed flies were maintained in a 20 x 20 x 20 cm insect cage, were provided with a solution of sucrose (50:50 v/v), and kept at 25°C, 95% RH and 16:8 D:L period. A random sample of the infected flies was taken at day 7 post-infection to verify the presence of parasites in the dissected gut. The chosen fly showed a high number of parasites when dissected and observed under light microscopy (Table). At day 13, infected sand flies were fed on a healthy anaesthetized hamster. In about 10 min, 4 flies were observed to have taken blood and were separated to be dissected. This practice was repeated at days 14, 18,...

Sandflies (Diptera: Psychodidae) in the Bar area of Montenegro (Yugoslavia). 2. Presence of promastigotes inPhlebotomus neglectusand first record ofP. kandelakii

“…The infected sandfly from Komina was freshly engorged when caught and had atypical flagellate parasites in its midgut. These parasites resembled the amastigotelike forms that Añez et al (2003) detected (after the flies had taken a parasite-free bloodmeal after the infective one) in the stomodeal valve and thoracic midgut of the P. papatasi they had experimentally infected with Le. major.…”

Stage-specific differential gene expression in Leishmania infantum: from the foregut of Phlebotomus perniciosus to the human phagocyte

“…In this case, the term pre-adaptation is understood to be the preparation in advance for intracellular survival once infection and differentiation to amastigotes occur. In fact, it has been reported that in some cases, amastigote-like forms are found within the population of metacyclic promastigotes located in the gut section anterior to the stomodeal valve of P. papatasi infected with L. major , which is most likely induced by respective slight temperature increase and a pH decrease after the female sand fly feeds [ 48 ]. This is in agreement with our previous findings about the effects of temperature and pH in the transcriptome during differentiation in L. infantum [ 16 ].…”