Population genetics and genomic of Triatoma brasiliensis (Hemiptera, Reduviidae) in an area of high pressure of domiciliary infestation in Northeastern Brazil

Author(s)

Maria Carolina Viana Alves

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2024-06-24

Examining board members

Carlos Eduardo Almeida; Vera Nisaka Solferini; Danilo Ciccone Miguel; Jader de Oliveira; Kaio Cesar Chaboli Alevi

• Advisor: Carlos Eduardo Almeida

Abstract

Understanding the population dynamics of vectors is crucial for the effective control of diseases transmitted by them. In the semi-arid northeastern region of Brazil, the triatomine insect Triatoma brasiliensis Neiva, 1911 persists as the most significant vector of Chagas disease, often presenting with persistent household infestation. Recent analyses of microsatellites and the mitochondrial gene Cytochrome b (MT-CYB) detected gene flow between T. brasiliensis populations from sylvatic and domiciliary environments in the state of Rio Grande do Norte (RN), raising relevant public health concerns. In the municipality of Currais Novos (RN), a high prevalence of peridomiciliary reinfestations by T. brasiliensis together with high rates of infection by Trypanosoma cruzi were observed, making this a worrying scenario as sylvatic populations represent a focus of reinfestation difficult to access. Therefore, we assessed the distribution of genetic variation via Sanger sequencing of the MT-CYB gene (n = 109) and high-throughput sequencing of single-nucleotide polymorphisms (SNPs, n = 86) to assess gene flow between distinct populations distributed in geographic areas and varied environments, mainly sylvatic and peridomiciliary. The samples available for analysis were previously collected from the rural communities of Currais Novos, within a radius of 16 km, and included 14 sampling points: two domiciliary, eight peridomiciliary, and four sylvatic. Furthermore, we included an external population located 220 km from the study area. Through AMOVA analysis of MT-CYB gene variation, we identified four distinct population groups with statistical significance (FCT= 0.42; p<0.05). Using the method employed to obtain SNP information based on ddRAD-seq genotyping-by-sequencing (GBS), which allows genome-wide analysis to infer genetic variation, we identified a total of 3,013 SNPs, with 11 loci putatively under selection. The variation based on 3,002 neutral loci showed a lack of genetic structure based on low FST values (p>0.05), indicating local panmixis. However, three samples from the external population were assigned to a cluster contrasting with those supposedly under local panmixia (>98%), validating the genomic marker recently applied for studies on population genetics at more precise levels of resolution for T. brasiliensis. The presence of population structure in some of the sampled points, as suggested by the mitochondrial marker, leads us to assume that the infestations were probably initiated by small populations of females, whose demographic event represents a risk of rapid reinfestations. The local panmictic pattern revealed by the GBS marker represents a challenge for vector control measures because reinfestation foci can be distributed over a wide geographic and ecological area. In our dataset, the results demonstrated that the genetic signals of both markers were complementary. Therefore, it is essential to consider the nature and pattern of inheritance of each marker when inferring the pattern of reinfestations (AU)

• FAPESP's process: 18/04594-6 - An integrative approach to morphological and molecular diversity of Triatoma brasiliensis, the main Chagas Disease vector in the Brazilian semiarid: elucidating links along the epidemiological chain
• Grantee: Maria Carolina Viana Alves
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)