Bartholomeu, D. C. | bioRxiv Science

bioRxiv2018

Detection of multiple circulating Leishmania species in Lutzomyia longipalpis in the city of Governador Valadares, southeastern Brazil

BackgroundLeishmaniasis encompasses a group of diverse clinical diseases caused by protozoan parasites of the Leishmania genus. This disease is a major public health problem in the New World affecting people exposed in endemic regions. The city of Governador Valadares (Minas Gerais/Brazil) is a re-emerging area for visceral leishmaniasis, with 191 human cases reported from 2008 to 2017 and a lethality rate of 14.7%. The transmission of the parasite occurs intensely in this region with up to 22% of domestic dogs with positive serology for the visceral form. Lu. longipalpis is one of the most abundant sand fly species in this area. Despite this scenario, so far there is no information regarding the circulating Leishmania species in the insect vector Lutzomyia longipalpis in this focus.\n\nMethodology/Principal FindingsWe collected 616 female Lutzomyia longipalpis sand flies between January and September 2015 in the Vila Parque Ibituruna neighborhood (Governador Valadares/MG), which is located on a transitional area between the sylvatic and urban environments with residences built near a preserved area. After DNA extraction of individual sand flies, the natural Leishmania infections in Lu. longipalpis were detected by end-point PCR, using primers derived from kDNA sequences, specific for L. (Leishmania) or L. (Viannia) subgenus. The sensitivity of these PCR reactions was 0.1 pg of DNA for each Leishmania subgenus and the total infection rate of 16.2% (100 positive specimens). Species-specific PCR detected the presence of multiple Leishmania species in infected Lu. longipalpis specimens in Governador Valadares, including L. amazonensis (n=3), L. infantum (n=28), L. (Viannia) spp. (n=20), coinfections with L. infantum and L. (Viannia) spp. (n=5), and L. (Leishmania) spp (n=44).\n\nConclusionsOur results demonstrate that multiple Leishmania species circulate in Lu. longipalpis in Governador Valadares and reveal a potential increasing risk of transmission of the different circulating parasite species. This information is a key factor for planning surveillance and effective control strategies against leishmaniasis in this endemic focus.\n\nAuthor summaryLeishmaniasis is a neglected tropical disease transmitted to mammals by the bite of sand flies infected with parasites of the Leishmania genus. This disease affects millions of people in various regions of the world, including Brazil. The municipality of Governador Valadares (Minas Gerais/Brazil) is a re-emergent focus of intense transmission of leishmaniasis, with a high number of human cases and a high prevalence of infected domestic dogs. To develop better leishmaniasis control strategies for the region, we performed a surveillance study of Lu. longipalpis, the main vector of visceral leishmaniasis in Brazil, and identified circulating species of Leishmania in this insect vector. We estimate that the natural infection rate of Lu. longipalpis for these parasites was of 16.2% in the study area. We also detected the presence of multiple circulating Leishmania species (L. amazonensis, L. infantum and Viannia subgenus) in Lu. longipalpis in Governador Valadares city, including 5 sand flies coinfected with L. infantum and L. (Viannia). Thus, our results reinforce the need for a rigid and systematic control of the sand flies monitoring in this area, due to the potential risk of transmission of different species of the Leishmania parasites.

epidemiology↗

bioRxiv2018

Repeat-driven generation of antigenic diversity in a major human pathogen, Trypanosoma cruzi

Trypanosoma cruzi, a zoonotic kinetoplastid protozoan with a complex genome, is the causative agent of American trypanosomiasis (Chagas disease). The parasite uses a highly diverse repertoire of surface molecules, with roles in cell invasion, immune evasion and pathogenesis. Thus far, the genomic regions containing these genes have been impossible to resolve and it has been impossible to study the structure and function of the several thousand repetitive genes encoding the surface molecules of the parasite. We here present an improved genome assembly of a T. cruzi clade I (TcI) strain using high coverage PacBio single molecule sequencing, together with Illumina sequencing of 34 T. cruzi TcI isolates and clones from different geographic locations, sample sources and clinical outcomes. Resolution of the surface molecule gene structure reveals an unusual duality in the organisation of the parasite genome, a core genomic region syntenous with related protozoa flanked by unique and highly plastic subtelomeric regions encoding surface antigens. The presence of abundant interspersed retrotransposons in the subtelomeres suggests that these elements are involved in a recombination mechanism for the generation of antigenic variation and evasion of the host immune response. The comparative genomic analysis of the cohort of TcI strains revealed multiple cases of such recombination events involving surface molecule genes and has provided new insights into T. cruzi population structure.

genomics↗

bioRxiv2017

ProphET, Prophage Estimation Tool: a standalone prophage sequence prediction tool with self-updating reference database

Prophages are a significant force in prokaryote evolution. The remaining sequences of a bacteriophage integration event are known for altering gene expression, enabling creative destruction of the bacterial genome and to induce pathogenicity by harboring and transposing virulence and antibiotic resistance factors. In the light of the dreadful expansion of antibiotic resistance bacteriophages have gathered renewed interest from the scientific community and public health decision makers as a promising long forgotten alternative to control bacterial infections. Cataloging the repertoire of prophages and their integration sites is an important initial step in the understanding of bacteriophages either as tool or as a threat. In this work, we present ProphET (Prophage Estimation Tool), a standalone application without the limitations of their web based counterparts and which identifies prophages in bacterial genomes with higher precision than similar applications.

bioinformatics↗