Assessing the mitochondrial DNA diversity of the Chagas disease vector Triatoma sordida (Hemiptera: Reduviidae).

Triatoma sordida is a species that transmits Trypanosoma cruzi to humans. In Brazil, T. sordida currently deserves special attention because of its wide distribution, tendency to invade domestic environments and vectorial competence. For the planning and execution of control protocols to be effective against Triatominae, they must consider its population structure. In this context, this study aimed to characterise the genetic variability of T. sordida populations collected in areas with persistent infestations from Minas Gerais, Brazil. Levels of genetic variation and population structure were determined in peridomestic T. sordida by sequencing a polymorphic region of the mitochondrial cytochrome b gene. Low nucleotide and haplotype diversity were observed for all 14 sampled areas; π values ranged from 0.002-0.006. Most obtained haplotypes occurred at low frequencies, and some were exclusive to only one of the studied populations. Interpopulation genetic diversity analysis revealed strong genetic structuring. Furthermore, the genetic variability of Brazilian populations is small compared to that of Argentinean and Bolivian specimens. The possible factors related to the reduced genetic variability and strong genetic structuring obtained for studied populations are discussed in this paper.

Assessing the mitochondrial DNA diversity of the Chagas disease vector Triatoma sordida (Hemiptera: Reduviidae)

Triatoma sordida is a species that transmits Trypanosoma cruzi to humans. In Brazil, T. sordida currently deserves special attention because of its wide distribution, tendency to invade domestic environments and vectorial competence. For the planning and execution of control protocols to be effective against Triatominae, they must consider its population structure. In this context, this study aimed to characterise the genetic variability of T. sordida populations collected in areas with persistent infestations from Minas Gerais, Brazil. Levels of genetic variation and population structure were determined in peridomestic T. sordida by sequencing a polymorphic region of the mitochondrial cytochrome b gene. Low nucleotide and haplotype diversity were observed for all 14 sampled areas; π values ranged from 0.002-0.006. Most obtained haplotypes occurred at low frequencies, and some were exclusive to only one of the studied populations. Interpopulation genetic diversity analysis revealed strong genetic structuring. Furthermore, the genetic variability of Brazilian populations is small compared to that of Argentinean and Bolivian specimens. The possible factors related to the reduced genetic variability and strong genetic structuring obtained for studied populations are discussed in this paper.

Susceptibility of Triatoma brasiliensis from state of Ceará, Northeastern Brazil, to the pyrethroid deltamethrin.

After controlling Triatoma infestans in Brazil, other species of triatomine that were considered minor in the transmission of Chagas disease became important. The persistence of Triatoma brasiliensis in Northeastern Brazil, associated with reinfection of domestic environments recently sprayed with pyrethroids, may be a signal of susceptibility alteration of this species to this insecticide. Specimens of T. brasiliensis from the municipality of Tauá, state of Ceará, were captured before and one year after spraying. They were submitted to bioassays using deltamethrin. The LD50 ranged from 0.19-0.33 ng of deltamethrin/nymph. The resistance ratio among samples from Tauá varied from 1.16-1.79 in the samples captured before the spraying and 1.00-1.74 in the samples captured one year after spraying, demonstrating that the two populations were equally susceptible to deltamethrin. The small difference in susceptibility between the two captures suggests that T. brasiliensis obtained in the second capture are from new invasions of the domestic environment and that the insecticide did not select resistant individuals. Therefore, it is suggested that T. brasiliensis control be carried out supplementing the regular use of pyrethroids with complementary measures, such as improvement of the dwellings and health education.

Susceptibility of Triatoma brasiliensis from state of Ceará, Northeastern Brazil, to the pyrethroid deltamethrin

After controlling Triatoma infestans in Brazil, other species of triatomine that were considered minor in the transmission of Chagas disease became important. The persistence of Triatoma brasiliensis in Northeastern Brazil, associated with reinfection of domestic environments recently sprayed with pyrethroids, may be a signal of susceptibility alteration of this species to this insecticide. Specimens of T. brasiliensis from the municipality of Tauá, state of Ceará, were captured before and one year after spraying. They were submitted to bioassays using deltamethrin. The LD50 ranged from 0.19-0.33 ng of deltamethrin/nymph. The resistance ratio among samples from Tauá varied from 1.16-1.79 in the samples captured before the spraying and 1.00-1.74 in the samples captured one year after spraying, demonstrating that the two populations were equally susceptible to deltamethrin. The small difference in susceptibility between the two captures suggests that T. brasiliensis obtained in the second capture are from new invasions of the domestic environment and that the insecticide did not select resistant individuals. Therefore, it is suggested that T. brasiliensis control be carried out supplementing the regular use of pyrethroids with complementary measures, such as improvement of the dwellings and health education.

Susceptibility of triatoma infestans to deltamethrin in Rio Grande do Sul, Brazil.

Strategies for controlling Chagas disease are based on spraying infested houses with pyrethroid insecticides. However, the intense use of these insecticides has promoted resistance of Triatoma infestans and, in Argentina, Bolivia and Southern Brazil, low levels of resistance have been reported. Due to the persistence of T. infestans in the state of Rio Grande do Sul (RS), we evaluated the occurrence of deltamethrin resistance in four strains from different municipalities in comparison to two susceptible strains from Brazil and one resistant strain from Bolivia. The results indicated the absence of resistance in T. infestansfrom RS.

Susceptibility of Triatoma infestans to deltamethrin in Rio Grande do Sul, Brazil

Strategies for controlling Chagas disease are based on spraying infested houses with pyrethroid insecticides. However, the intense use of these insecticides has promoted resistance of Triatoma infestans and, in Argentina, Bolivia and Southern Brazil, low levels of resistance have been reported. Due to the persistence of T. infestans in the state of Rio Grande do Sul (RS), we evaluated the occurrence of deltamethrin resistance in four strains from different municipalities in comparison to two susceptible strains from Brazil and one resistant strain from Bolivia. The results indicated the absence of resistance in T. infestans from RS.

Triatoma infestans e Triatoma brasiliensis: avaliação da resistência ao piretróide deltametrina e análise intraespecífica da variabilidade genética

O Programa de Controle da Doença de Chagas (PCDCh) teve suas atividades. iniciadas por volta da década de 1960 em âmbito nacional. Em 1991, com a. Iniciativa dos Países do Cone Sul, o PCDCh passou a priorizar as áreas de. ocorrência do Triatoma infestans, enquanto a vigilância epidemiológica era. implantada nas áreas já sob controle da transmissão vetorial. A utilização de. inseticidas piretróides nas atividades de controle permitiram ao PCDCh obter. resultados satisfatórios, como a interrupção da transmissão vetorial da doença de. Chagas em amplas áreas. A preocupação atual refere-se á possibilidade de. desenvolvimento de resistência aos inseticidas utilizados devido à existência de uma. região abrangendo o norte da Argentina e o sul da Bolívia onde T. infestans. apresenta-se resistente aos piretróides. Além disso, outras espécies de triatomíneos. já foram descritas com resistência inicial a estes inseticidas (ex. Rhodnius prolixus. na Venezuela e Triatoma sordida em Minas Gerais). Estas informações nos. impulsionaram a avaliar as populações remanescentes de T. infestans do Rio. Grande do Sul, comparando-as com amostras resistentes da Argentina e Bolívia, e. amostras de Triatoma brasiliensis do Ceará, através de ensaios com o piretróide. deltametrina.

Complementarmente, foi estudada a variabilidade genética das. populações através de sequências do gene mitocondrial cytB e microssatélites. Os. resultados dos ensaios com deltametrina demonstraram que todas as amostras de. T. infestans e T. brasiliensis do Brasil apresentaram-se suscetíveis ao inseticida. A. variabilidade genética para T. infestans foi baixa, com valores muito inferiores aos. observados em T. brasiliensis. Também foi verificado que a variabilidade genética. demonstrada através dos loci de microssatélites em T. infestans foi muito maior que a apresentada pelas sequências do gene cytB. Apesar disso, a análise das sequências deste gene se mostrou adequada para avaliar a diferenciação genética das populações. Em nosso trabalho foram observados valores de resistência menores dos já descritos para T. infestans do Rio Grande do Sul e da Bolívia. Estas diferenças indicam que o fenômeno de resistência é muito mais complexo do que se imaginava, e por isso merece maior atenção

Triatoma infestans e Triatoma brasiliensis: avaliação da resistência ao piretróide deltametrina e análise intraespecífica da variabilidade genética / Triatoma infestans and Triatoma brasiliensis: assessing resistance to pyrethroid deltamethrin and analysis of intraspecific genetic variability

O Programa de Controle da Doença de Chagas (PCDCh) teve suas atividades. iniciadas por volta da década de 1960 em âmbito nacional. Em 1991, com a. Iniciativa dos Países do Cone Sul, o PCDCh passou a priorizar as áreas de. ocorrência do Triatoma infestans, enquanto a vigilância epidemiológica era. implantada nas áreas já sob controle da transmissão vetorial. A utilização de. inseticidas piretróides nas atividades de controle permitiram ao PCDCh obter. resultados satisfatórios, como a interrupção da transmissão vetorial da doença de. Chagas em amplas áreas. A preocupação atual refere-se á possibilidade de. desenvolvimento de resistência aos inseticidas utilizados devido à existência de uma. região abrangendo o norte da Argentina e o sul da Bolívia onde T. infestans. apresenta-se resistente aos piretróides. Além disso, outras espécies de triatomíneos. já foram descritas com resistência inicial a estes inseticidas (ex. Rhodnius prolixus. na Venezuela e Triatoma sordida em Minas Gerais). Estas informações nos. impulsionaram a avaliar as populações remanescentes de T. infestans do Rio. Grande do Sul, comparando-as com amostras resistentes da Argentina e Bolívia, e. amostras de Triatoma brasiliensis do Ceará, através de ensaios com o piretróide. deltametrina.

Complementarmente, foi estudada a variabilidade genética das. populações através de sequências do gene mitocondrial cytB e microssatélites. Os. resultados dos ensaios com deltametrina demonstraram que todas as amostras de. T. infestans e T. brasiliensis do Brasil apresentaram-se suscetíveis ao inseticida. A. variabilidade genética para T. infestans foi baixa, com valores muito inferiores aos. observados em T. brasiliensis. Também foi verificado que a variabilidade genética. demonstrada através dos loci de microssatélites em T. infestans foi muito maior que a apresentada pelas sequências do gene cytB. Apesar disso, a análise das sequências deste gene se mostrou adequada para avaliar a diferenciação genética das populações. Em nosso trabalho foram observados valores de resistência menores dos já descritos para T. infestans do Rio Grande do Sul e da Bolívia. Estas diferenças indicam que o fenômeno de resistência é muito mais complexo do que se imaginava, e por isso merece maior atenção

Population dynamics of Triatoma vitticeps (Stål, 1859) in Itanhomi, Minas Gerais, Brazil.

Taxonomic markers (head structure morphometry, isoenzymes and randon amplified polymorphism of DNA - RAPD) were used to understand the population dynamics of Triatoma vitticeps, predominant triatomine species in Itanhomi district, using samples obtained from domestic, peridomiciliary and sylvatic habitats. Morphometric analysis revealed sexual dimorphism within the three samples although specimens could not be separated according to the habitat in which they were captured. Forty-two bands were analyzed from RAPD profiles generated using four primers. A dendrogram constructed from Dice's similarity coefficient values showed that migration of the insects between the habitats has occurred, without structuring of populations. Moreover, the dendrogram obtained from the genetic distance values showed an important gene flow between the sylvatic and domestic habitats. No polymorphism was found in the electrophoretic mobility of proteins for the ten enzymes studied. Our results revealed movement of triatomines between the three habitats, suggesting that the presence of T. vitticeps in houses should not be ignored. As invasion of houses by sylvatic insects is frequent and the natural infection indices of this species are among the highest known, epidemiological vigilance studies may reveal possible changes in T. vitticeps behaviour which could present future risks to public health.

Population dynamics of Triatoma vitticeps (Stål, 1859) in Itanhomi, Minas Gerais, Brazil

Taxonomic markers (head structure morphometry, isoenzymes and randon amplified polymorphism of DNA - RAPD) were used to understand the population dynamics of Triatoma vitticeps, predominant triatomine species in Itanhomi district, using samples obtained from domestic, peridomiciliary and sylvatic habitats. Morphometric analysis revealed sexual dimorphism within the three samples although specimens could not be separated according to the habitat in which they were captured. Forty-two bands were analyzed from RAPD profiles generated using four primers. A dendrogram constructed from Dice's similarity coefficient values showed that migration of the insects between the habitats has occurred, without structuring of populations. Moreover, the dendrogram obtained from the genetic distance values showed an important gene flow between the sylvatic and domestic habitats. No polymorphism was found in the electrophoretic mobility of proteins for the ten enzymes studied. Our results revealed movement of triatomines between the three habitats, suggesting that the presence of T. vitticeps in houses should not be ignored. As invasion of houses by sylvatic insects is frequent and the natural infection indices of this species are among the highest known, epidemiological vigilance studies may reveal possible changes in T. vitticeps behaviour which could present future risks to public health.

Genetic structure of natural populations of the sand fly Lutzomyia longipalpis (Diptera: Psychodidae) from the Brazilian northeastern region.

In Latin America, Lutzomyia longipalpis is the principal vector of Leishmania chagasi, and is associated with the majority of active foci of visceral leishmaniasis. In spite of the fact that this sand fly is spread practically throughout the entire Neotropical Region, its distribution is not uniform due to geographic and environmental barriers. Geographic isolation coupled with reduced flight abilities may contribute to the appearance of cryptic species of Lutzomyia longipalpis, which may differ in their capacity to transmit L. chagasi. In this work, we describe the genetic structuring patterns based on polymorphism analysis of 24 RAPD-PCR loci of 7 natural populations of Lutzomyia longipalpis obtained from Brazil's northeastern region. The estimated degree of genetic differentiation between populations, based on the population subdivision index theta(ST) (0.136), suggests a moderate degree of genetic structuring as a result of geographical isolation and restricted gene flow. Genetic distances were found to be compatible with those found between members of a single species, suggesting a taxonomic uniformity of Lutzomyia longipalpis in the region studied.