Dynamics of Panstrongylus megistus infestation, the primary vector of Trypanosoma cruzi in Minas Gerais, Brazil.

Panstrongylus megistus is considered one of the primary species of epidemiological importance for the transmission of Chagas disease in Brazil due to its wide geographical distribution throughout the national territory, good ability to invade and colonize houses, and high rates of natural infection by the Trypanosoma cruzi. The importance of this species in Minas Gerais has been recognized since the 80s. It is responsible for the high prevalence rates of Chagas disease in the west of the state. Studies conducted in the municipality of Jaboticatubas show that P. megistus is still the most captured vector in the region, even after 40 years of uninterrupted actions of the Chagas Disease Control Program in the municipality. Despite the importance of the species, its population dynamics is little studied. Consequently, crucial genetic information such as genetic diversity and gene flow among environments have not been well characterized yet. In this context, this work presents a population genetic analysis at the microgeographic level using microsatellite markers in samples of P. megistus obtained from Jaboticatubas to better understand the infestation dynamics of the primary vector species of T. cruzi in the region. The observed and expected heterozygosity ranged from 0.26 to 0.47 and 0.47 to 0.65, respectively. Most loci presented Hardy-Weinberg disequilibrium due to the excess of homozygotes. The pairwise Fst ranged from 0.05 to 0.35, with the p value significant for all comparisons, indicating the absence of gene flow between them. The values of Fis found ranged from 0.25 to 0.52, all values of p ≤ 0.05, probably due to structured populations, inbreeding, or null alleles. The results suggest an extended stay of this species in the colonized environments, with rare dispersal to other locations. Such results differ from that observed for Triatoma brasiliensis and Triatoma dimidiata, species that present constant movement, even after colonization of the artificial environment, and are similar to the behavior of Triatoma infestans. Thus, the study reinforces the importance of continuous entomological surveillance in the areas of occurrence of P. megistus to avoid the installation and formation of new foci of household infestation in the region.

Identification and characterization of microsatellite markers for population genetic studies of Panstrongylus megistus (Burmeister, 1835) (Triatominae: Reduviidae).

BACKGROUND: Panstrongylus megistus is the most important vector of Chagas disease in Brazil. Studies show that the principal factor hindering the control of triatomines is reinfestation of houses previously treated with insecticides. Studies at the microgeographic level are therefore necessary to better understand these events. However, an efficient molecular marker is not yet available for carrying out such analyses in this species. The aim of the present study was to identify and characterize microsatellite loci for future population genetic studies of P. megistus. METHODS: This study work consisted of five stages: (i) sequencing of genomic DNA; (ii) assembly and selection of contigs containing microsatellites; (iii) validation of amplification and evaluation of polymorphic loci; (iv) standardization of the polymorphic loci; and (v) verification of cross-amplification with other triatomine species. RESULTS: Sequencing of males and females generated 7,908,463 contigs with a total length of 2,043,422,613 bp. A total of 2,043,690 regions with microsatellites in 1,441,091 contigs were obtained, with mononucleotide repeats being the most abundant class. From a panel of 96 loci it was possible to visualize polymorphisms in 64.55% of the loci. Of the 20 loci genotyped, the number of alleles varied from two to nine with an average of 4.9. Cross-amplification with other species of triatomines was observed in 13 of the loci. CONCLUSIONS: Due to the high number of alleles encountered, polymorphism and the capacity to amplify from geographically distant populations, the microsatellites described here show promise for utilization in population genetic studies of P. megistus.

Microsatellite variation revealed panmictic pattern for Triatoma brasiliensis (Triatominae: Reduviidae) in rural northeastern Brazil: the control measures implications.

BACKGROUND: Triatoma brasiliensis Neiva, 1911 is the main vector of Trypanosoma cruzi in the caatinga of Northeastern Brazil. Despite of its epidemiological relevance, there are few studies on its genetic variability. Using microsatellite markers, we characterized the variability and dynamics of infestation and reinfestation of T. brasiliensis after residual insecticide spraying in five surveys conducted in a well-defined rural area located in the municipality of Tauá, Ceará, between 2009 and 2015. We evaluated: (1) general variability among local of captures; (2) variability along the time analysis (2009, 2010 and 2015); (3) and reinfestation process. RESULTS: On the analysis (1) global and pairwise FST values suggested absence of clusters among the area. AMOVA indicated that total variation is mainly represented by individual differences. Absence of clustering indicates a panmitic unit, with free gene flow. For (2), Pairwise FST indicated alterations in the genetic profile of the triatomines along the time. (3) Analysis of the reinfestation process showed that the domiciliary units investigated had different sources of infestation despite of its proximity. CONCLUSIONS: Observed homogeneity can be explained by the great dispersal capacity of T. brasiliensis, overlapping the different environments. Persistent house infestation in Tauá may be attributed to the occurrence of postspraying residual foci and the invasion of triatomines from their natural habitats.

Genetic characterization of residual Triatoma infestans populations from Brazil by microsatellite.

In spite of long-term efforts to eliminate Triatoma infestans (Klug 1834) from Brazil, residual foci still persist in the states of Bahia and Rio Grande do Sul. Data on the genetic variability and structuring of these populations are however lacking. Using nine microsatellite loci, we characterized one residual T. infestans population from Bahia and four from Rio Grande do Sul, and compared them with bugs originally from an older focus in São Paulo; 224 bugs were genotyped. The number of alleles per locus ranged from 5 to 11. Observed and expected heterozygosities per locus ranged, respectively, from 0 to 0.786 and from 0 to 0.764. Significant departures from Hardy-Weinberg equilibrium, mainly due to heterozygote deficits, were detected in all loci and in most populations. Global indices estimated by AMOVA were: Fis was 0.37; Fst was 0.28; and Fit was 0.55; overall indices with p = 0.00 indicated substantial differentiation. Inter-population Fst ranged from 0.118 to 0.562, suggesting strong genetic structuring and little to no gene flow among populations. Intra-population Fis ranged from 0.301 to 0.307. Inbreeding was apparent in all populations except that from Bahia-which might be either linked by gene flow to nearby unsampled populations or part of a relatively large local population. The overall pattern of strong genetic structuring among pyrethroid-susceptible residual T. infestans populations suggests that their persistence is probably due to operational control failures. Detection and elimination of such residual foci is technically feasible and must become a public health priority in Brazil.

Markers for the population genetics studies of Triatoma sordida (Hemiptera: Reduviidae).

BACKGROUND: Triatoma sordida, a vector of Trypanosoma cruzi, is native of Brazil, Bolivia, Paraguay, Argentina, and Uruguay, and occurs primarily in peridomiciles. Currently, it is the species most frequently captured by the Chagas Disease Control Program in Brazil. For this reason, population genetic studies attract great interest, as they can provide further information about the dispersal and household invasion processes of this species. In the absence of suitable markers, the objective of this study was to test the cross amplification of microsatellite primers. FINDINGS: 23 primers were tested for microsatellite loci already described for other species of the genus Triatoma sp. Forty four specimens of T. sordida captured in the north of Minas Gerais were used to validate the use of standardized loci for population genetic analyses. It was possible to amplify 10 of the 23 loci tested for T. sordida. CONCLUSIONS: This is the first study that provides 10 microsatellite markers for population analysis of this triatomine species. Cross-amplification of primers can be used among other phylogenetically related species whose loci are already available for study.

Profile of the Trypanosoma cruzi vector infestation in Jaboticatubas, State of Minas Gerais, Brazil.

INTRODUCTION: This work aimed to analyze the triatomine infestation scenario in Jaboticatubas after 30 years of the uninterrupted actions of the Program of Chagas Disease Control. METHODS: From 2007 to 2010, household unit infestation was researched, and an exploratory analysis of the localities infested with Panstrongylus megistus was performed. RESULTS: In total, 613 triatomines were captured in 78 households, the majority of which were Panstrongylus megistus and were captured mainly in chicken houses, but they were also found to be colonizing human houses. CONCLUSIONS: The epidemiological importance of Panstrongylus megistus was confirmed in Jaboticatubas, and capability to colonize indoors has been demonstrated, as has its proximity to humans. Its distribution is aggregated in the northern and in central-eastern regions of the municipality.

Cenário ecoepidemiológico da doença de Chagas no entorno do Parque Nacional da Serra do Cipó, Minas Gerais,Brasil

A doença de Chagas (DC) é uma enfermidade causada pelo protozoário Trypanosoma cruzi,cuja principal forma de transmissão é através das fezes de triatomíneos infectados. O Panstrongylus megistus atualmente é o principal vetor do Brasil, sendo responsável pela transmissão da DC na região da Serra do Cipó, MG, na década de 80. O P. megistus possui alta capacidade de reinfestação das casas, exigindo permanente vigilância contra a instalação de novos focos. O peridomicílio apresenta grande importância para a manutenção de triatomíneos e do T. cruzi circulando entre barbeiros e os animais que o frequentam. O objetivo do trabalho foi avaliar o cenário ecoepidemiológico da doença de Chagas noentorno do Parque Nacional da Serra do Cipó (ParnaCipó), visando subsidiar o programa de controle do P. megistus. O estudo se realizou nos municípios de Jaboticatubas e Santana do Riacho que, juntamente com Morro do Pilar e Itambé do Mato Dentro, integram o ParnaCipó. O perfil de infestação pelo P. megistus foi determinado através de captura de triatomíneos nas unidades domiciliares (setembro de 2007 a setembro de 2010) e capturas silvestres, que também incluiram avaliação da infecção em marsupiais e roedores.

Cães levados à campanha de vacinação antirrábica de Jaboticatubas foram examinados a fim de determinar sua importância epidemiológica na região. Exemplares de P. megistus capturados foram utilizados para análise populacional pela morfometria geométrica. Os exemplares provenientes de Jaboticatubas foram ainda analisados por RAPD para estudo populacional. As cepas isoladas dos reservatórios e vetores foram caracterizadas como pertencentes ao grupo T. cruzi I ou T. cruzi II utilizando‐se DNA satélite como alvo. A maioria dos exemplares P. megistus foi capturada em galinheiros; no intradomicílio o ecótopo preferencial foi o quarto. Foram realizadas pesquisas em 15 áreas silvestres com a captura de 105 mamíferos, com taxa de infecção de 6,7%; todas as cepas foram caracterizadas como T. cruzi I. A prevalência em cães foi de 2,4%. Em palmeiras foram capturados Rhodnius neglectus, P. megistus e Triatoma sordida. Dentre as cepas isoladas de triatomíneos domiciliados e silvestres, apenas uma cepa proveniente do ambiente domiciliar foi caracterizada como T. cruzi II, as demais, T. cruzi I. A morfometria diferenciou a população silvestre das domiciliares. A RAPD demonstrou grande variabilidade dos P. megistus de Jaboticatubas, entretanto, sem diferenciação populacional. Frente aos resultados, podemos concluir que a população rural dos dois municípios permanece sob o risco de infecção pelo T. cruzi, uma vez que são encontrados vetores e reservatórios infectados no ambiente artificial e natural, e podem infestar as habitações a partir de diversos focos, domiciliares ou silvestres.

Influence of the palm tree species on the variability of Rhodnius nasutus Stål, 1859 (Hemiptera, Reduviidae, Triatominae).

This work evaluated the occurrence and genetic structure of Rhodnius nasutus sampled in two sites using morphometry and microsatellites. These sites, presented distinct abiotic features and palm trees: (i) nine Attalea speciosa palm trees, so called babaçu, were sampled from the Meruoca Mountain Ridge, a sloping region of reminiscent forest in the state of Ceará, Brazil, and (ii) 17 Copernicia prunifera palm trees, so called carnaúba, were sampled in the scrub savanna region (Sobral district) that surrounds the mountain ridge. Of the twenty-six palm trees dissected, 70.6% of carnauba and 88.9% of babaçu were infested by R. nasutus. The micro-climatic data where R. nasutus were sheltered demonstrated that the babaçu and carnaúba palm trees presented significant differences (p < 0.05) in relation to the external environment, except for temperature and relative humidity regulation, suggesting that the architecture of the babaçu crown keeps a more stable micro-environment. The morphometric studies of the F1 generation demonstrated that insects from the babaçu (A. speciosa) were significantly larger (p = 0.000) than those collected in carnaúba (C. prunifera) palm trees. Also, microsatellite analysis demonstrated a high genetic differentiation between the two groups of R. nasutus (R(st) = -0.77). Our results suggest that the difference in size between the populations is probably related to an incipient process of genetic drift in populations associated to each palm tree, probably also driven by the different climatic features observed in these micro-environments.

Biological aspects of crosses between Triatoma maculata (Erichson, 1848) and Triatoma pseudomaculata Corrêa & Espínola, 1964 (Hemiptera: Reduviidae).

Due to morphological similarities between Triatoma maculata and T. pseudomaculata, which comprise the "maculate complex", both had been regarded as the same species until 1964. Considering that the studies on triatomine hybridization permit hypotheses formulation concerning origin and divergence of species, enabling a quantitative analysis of taxonomic relationships between species, the present investigation was aimed at broadening further understanding related to the capacity of hybrid production by determining the degree of reproductive isolation between T. maculata and T. pseudomaculata. Our results have demonstrated that T. maculata and T. pseudomaculata showed no differences regarding reproduction patterns and they are able to cross, generating infertile hybrids.

Biological aspects of crosses between Triatoma maculata (Erichson, 1848) and Triatoma pseudomaculata Corrêa & Espínola, 1964 (Hemiptera: Reduviidae)

Due to morphological similarities between Triatoma maculata and T. pseudomaculata, which comprise the "maculate complex", both had been regarded as the same species until 1964. Considering that the studies on triatomine hybridization permit hypotheses formulation concerning origin and divergence of species, enabling a quantitative analysis of taxonomic relationships between species, the present investigation was aimed at broadening further understanding related to the capacity of hybrid production by determining the degree of reproductive isolation between T. maculata and T. pseudomaculata. Our results have demonstrated that T. maculata and T. pseudomaculata showed no differences regarding reproduction patterns and they are able to cross, generating infertile hybrids.

Caracterização morfológica e molecular de híbridos do cruzamento entre Triatoma maculata (Erichson, 1848) e Triatoma pseudomaculata (Corrêa & Espínola, 1964)(Hemiptera: Reduviidae) / Morphologic and molecular characterization of hybrids from the cross breeding among Triatoma maculata (Erichson, 1848) e Triatoma pseudomaculata (Corrêa & Espínola, 1964)(Hemiptera: Reduviidae)

Devido às suas grandes semelhanças morfológicas, Triatoma maculata e Triatoma pseudomaculata, que constituem para Carcavallo et al. (2000) o ´complexo maculata`, eram consideradas a mesma espécie até 1964 (Corrêa e Espínola, 1964). Essas espécies são alopátricas e, segundo Schofield (1988), T. maculata teria sido introduzida no Nordeste brasileiro por aves migratórias, com subseqüente especiação, e formação da espécie T. pseudomaculata. Estudos utilizando isoenzimas demonstraram grande distância genética entre as duas espécies e grande proximidade entre T. pseudomaculata e Triatoma wygodzinsky, com subseqüente proposta de reestruturação do ´complexo maculata`(Santos et al., 2003).Os estudos de cruzamentos entre em triatomíneos permitem a formulação de hipóteses acerca da origem e divergência de espécies e podem ajudar a entender a sistemática do grupo. O objetivo deste trabalho é determinar o grau de isolamento reprodutivo entre T. maculata e T. pseudomaculata, e caracterizar geneticamente as espécies e os híbridos obtidos pelos cruzamentos interespecíficos, permitindo o cotejamento de aspectos genéticos com características biológicas e comportamentais destes insetos. Os nossos resultados mostram que T. maculata e T. pseudomaculata não apresentam diferenças quanto à reprodução e são espécies que se cruzam produzindo híbridos inférteis. Os resultados dos cruzamentos intra e interespecíficos, da morfologia, da morfometria geométrica e da análise de RAPDs mostram T. maculata e T. pseudomaculata como espécies bem diferenciadas.Os híbridos obtidos são mais semelhantes morfologicamente à T. maculata, entretanto, geneticamente estão mais próximos à T. pseudomaculata. T. wygodzinsky e os híbridos obtidos com estas espécies foram os que se apresentaram mais distantes dos demais grupos estudados. Os resultados indicam que independentemente de uma origem evolutiva comum entre essas três espécies, atualmente elas estão bastante diferenciadas geneticamente e não devem...