Predominance of Leishmania (Leishmania) amazonensis DNA in Lutzomyia longipalpis sand flies (Diptera: Psychodidae) from an endemic area for leishmaniasis in Northeastern Brazil

Abstract

Leishmaniasis is a serious public health concern in the Northeastern region of Brazil, where the sand fly fauna is well studied, although few species have been identified as competent vectors. The detection of Leishmania spp. parasites in wild-caught sand flies could help sanitary authorities draw strategies to avoid the transmission of the parasites and, therefore, the incidence of leishmaniases. We detected Leishmania DNA in wild-caught sand flies and correlated that data with aspects of sand fly ecology in the Caxias municipality, Maranhao State, Brazil. The sand flies were sampled in the peridomicile (open areas in the vicinity of human residences) and intradomicile (inside the residences) from July/2019 to March/2020. Leishmania DNA was detected in females, targeting a fragment of the Internal Transcribed Spacer (ITS1) from ribosomal DNA. Among the fourteen species of sand flies identified, five (Lutzomyia longipalpis, Nyssomyia whitmani, Evandromyia evandroi, Micropygomyia trinidadensis, and Micropygomyia quinquefer) harbored DNA of Leishmania (Leishmania) amazonensis. The most abundant species in rural (Ny. whitmani: 35.2% and Ev. evandroi: 32.4%) and urban areas (Lu. longipalpis: 89.8%) are the permissive vectors of L. (L.) amazonensis, especially Ny. whitmani, a known vector of causative agents of cutaneous leishmaniasis. Although Lu. longipalpis is the vector of L. (L.) infantum, which was not detected in this study, its permissiveness for the transmission of L. (L.) amazonensis has been reported. We suspect that visceral leishmaniasis and cutaneous leishmaniasis are caused by L. (L.) amazonensis, and the transmission may be occurring through Lu. longipalpis, at least in the urban area.

Figure 1. – Location of the capture sites of phlebotomine sand flies in Povoado Mulata and Volta Redonda, municipality of Caxias, Maranhao State, Brazil.

Figure 2. – Identification of Leishmania (Leishmania) amazonensis DNA sequences in phlebotomine sand flies (A): Agarose gel (1%) showing amplified products of 300-350 bp with the Leishmania ITS1 primers. PC: positive control; NC: negative control; 1-7: positive phlebotomine sand fly samples. (B) Phylogenetic tree of ITS1 DNA sequences of Leishmania spp. amplified from phlebotomine sand flies captured in two areas, rural and urban, in the Caxias municipality, Maranhao State, reconstructed by the Neighbor-Joining method. The percentage of replicate trees in which the associated taxons clustered by a bootstrap test (1000 replicates) is shown next to the nodes. Branch lengths are in the same units as the evolutionary distances used to infer the phylogenetic tree. Haplotype 1, highlighted in bold, represents the only haplotype identified in all ITS-1 sequences (all positive samples). The brackets indicate sequences from the Mexican complex (including Leishmania (L.) amazonensis and Leishmania (L.) mexicana). Trypanosoma cruzi is the external group.

Figure 3. – Monthly distribution of phlebotomine sand fly species according to the collection area, rural (A), and urban (B).