Estudo da capacidade e competência de Lutzomyia longipalpis (DIPTERA: PSYCHODIDAE) como vetor de Leishmania (Leishmania) amazonensi

Abstract

Studies about vectorial capacity and competence for the transmission of certain parasites require laboratory colonization of their biological vectors. The sand fly Lutzomyia longipalpis is incriminated as the main vector of Leishmania (Leishmania) infantum, but it has been shown to be permissive for several Leishmania species that cause american cutaneous leishmaniasis (ACL). Therefore, we demonstrate the competence of Lu. longipalpis in transmitting Leishmania (Leishmania) amazonensis in mice, causing clinical manifestation of ACL in these animals. Initially, we stablished a colony of Lu. longipalpis from females sampled in the municipality of Raposa, MA, using CDC light traps. The colony produced ten generations (F10) from the parental generation (P). The first four generations showed the highest productivity. The whole life cycle lasted on average 28 + 0.5 days at 27°C and 80% relative humidity. Nonviable eggs represented more than 50% of the total number of eggs produced by the engorged females, while pupae had a mortality rate of only 2%. In the tests for vectorial capacity and competence 291 uninfected females of Lu. longipalpis of generation F1, F2 and F3 performed a first blood feeding on mice infected with Le. amazonensis (strain IFLA / BR / 1968 / PH8). After blood-feeding, 52.6% of the females were positive for Leishmania DNA. Of these, 17 (of which 58,8% were positive for Leishmania by dissection of the intestine) performed a second feeding on uninfected mice. At 27 days post-infection, one mouse presented leishmaniotic lesions. The limiting dilution test and immunohistopathological analyses confirmed the occurrence of Leishmania promastigote and amastigote forms, respectively, in the skin of the animal. Parasite DNA was also detected in lesions on paws and inguinal lymph node. DNA sequencing and analysis confirmed the Leishmania species infecting both insects and mice. Our results confirm that Lu. longipalpis can sustain infection and experimentally transmit Le. amazonensis to rodents, inducing leishmaniastic lesions. From the epidemiological perspective of the urban ACL, the successful transmission demonstrated supports the role of Lu. longipalpis as a vector of Le. amazonensis in the studied region and possibly in others throughout Brazil and the New World, where both sand fly and parasite are widespread.