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.

Infections by trypanosomatid (Kinetoplastida: Trypanosomatidae) in triatomines (Hemiptera: Triatominae): A spatiotemporal assessment in an endemic area for Chagas disease.

This research analysed the spatiotemporal distribution of triatomines infected by trypanosomatid parasites in an endemic region for Chagas disease, in the state of Pernambuco, Northeastern Brazil. The database included the total number of triatomines captured from intradomicile and peridomicile areas, as well as the infection rate (IR) by trypanosomatid. The Gi∗ by Getis-Ord method was used to statistically identify significant concentration clusters and the IR of triatomines by trypanosomatids. A generalized linear regression model with a binomial distribution was used to evaluate the probability of finding an IR by trypanosomatids. Overall, of 4,800 triatomines examined, trypanosomatid forms similar to Trypanosoma cruzi were detected in 10.29% of them, and the majority of positive specimens (98.17%) were collected at intradomicile. The geospatial analyses identified triatomines clusters in intradomicile and peridomicile environments. According to the logistic regression data for species (Panstrongylus lutzi, P. megistus, Triatoma brasiliensis and T. pseudomaculata), the probability of detection of T. cruzi infection remains constant in up to 50 specimens examined or more. The findings of this research revealed a scenario never studied in this area through this type of spatiotemporal analysis, which is essential to identify areas of vulnerability for the occurrence of these vectors and consequently for Chagas disease.

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.

Laboratory and field studies for the control of Chagas disease vectors using the fungus Metarhizium anisopliae.

Chagas disease is one of the most important insect-vectored diseases in Brazil. The entomopathogenic fungus Metarhizium anisopliae was evaluated against nymphs and adults of Panstrongylus megistus, Triatoma infestans, and T. sordida. Pathogenicity tests at saturated humidity demonstrated high susceptibility to fungal infection. The shortest estimates of 50% lethal time (LT50 ) for P. megistus varied from 4.6 (isolate E9) to 4.8 days (genetically modified strain 157p). For T. infestans, the shortest LT50 was 6.3 (E9) and 7.3 days (157p). For T. sordida, the shortest LT50 was 8.0 days (157p). The lethal concentration sufficient to kill 50% of T. infestans (LC50 ) was 1.9 × 107 conidia/ml for strain 157p. In three chicken coops that were sprayed with M. anisopliae, nymphs especially were well controlled, with a great population reduction of 38.5% after 17 days. Therefore M. anisopliae performed well, controlling Triatominae in both laboratory and field studies.

Investigando a presença de Trypanosoma cruzi em gambás-de-orelha- preta (Didelphis aurita) residentes em um parque urbano da cidade de São Paulo / Investigating the presence of Trypanosoma cruzi in black-eared opossums (Didelphis aurita) living in an urban park in the city of São Paulo.

The increasing appearance of Chagas disease insect vectors in the metropolitan region of São Paulo has led endemic control entities to be alarmed at the potential increase in the number of cases of the disease. Trypanosoma cruzi is a flagellated protozoan responsible of trypanosomiasis, which has as the main vectors hematophagous triatomines. In the recently reported colonies of Panstrongylus infestans in urban areas around São Paulo, most of them are carrying the protozoan. Mammals of the orders, Didelphimorphia and Cingulata are known as primitive reservoirs of T. cruzi, which is also found in Primates and Chiroptera. It is suggested that the dissemination of the protozoan to other species has occurred through predation and direct contact with physiological secretions contained in mucous membranes and lesions, since the secretions contained in paracloacal glands of marsupials are also an important contaminant material. The objective of this study were investigate the possible presence of the protozoan T. cruzi in blood samples of the Neotropical marsupial Didelphis aurita in the park of Instituto Butantan. For the analysis of hemoparasites, blood samples were collected from the caudal vein for 7 animals. The analysis were made with blood smears on histological slides fixed in methyl alcohol, and stained by the Giemsa method for observation by microscopy. No positive results were obtained for T. cruzi after analyzing the samples collected.

Com o crescente aparecimento de insetos vetores de doença de Chagas na região metropolitana de São Paulo, entidades de controle de endemias se alarmaram para o potencial aumento dos casos da doença em municípios da Grande São Paulo. O Trypanosoma cruzi é um protozoário flagelado responsável pela tripanossomíase, doença que possui como principais vetores os triatomíneos hematófagos. Recentemente, há relatos do aumento de colônias de Panstrongylus megistus nos municípios próximos a São Paulo, sendo que em grande parte deles foi encontrado o protozoário. Sabe-se que mamíferos das ordens Marsupialia e Cingulata são reservatórios primitivos do protozoário, havendo também registros em Primatas e Chiroptera. Sugere-se que a disseminação do protozoário para outras espécies tenha ocorrido através da predação e contato direto com secreções fisiológicas contidas em mucosas e lesões, sendo as secreções contidas nas glândulas paracloacais também um importante material contaminante. Este trabalho objetivou pesquisar o protozoário Trypanosoma cruzi nas amostras de sangue de Didelphis aurita do parque do Instituto Butantan Para a análise dos hemoparasitas, foram coletadas amostras de sangue da veia caudal. A análise foi feita a partir de esfregaço sanguíneo feito em lâminas histológicas fixadas em álcool metílico, sendo coradas pelo método Giemsa, e observadas através de microscopia óptica. Não foram obtidos resultados positivos para T. cruzi após a análise das amostras coletadas.

Trypanosoma cruzi isolated from a triatomine found in one of the biggest metropolitan areas of Latin America

Abstract: INTRODUCTION: To characterize Trypanosoma cruzi (TcI) isolated from a Panstrongylus megistus specimen found in one of the biggest metropolitan areas of Latin America, the relationship between the TcI group of T. cruzi and the transmission cycle in the urban environment was studied. METHODS: The T. cruzi strain, Pm, was isolated in a culture medium from the evolutionary forms present in the hindgut of a live male specimen of P. megistus found in the Jabaquara subway in São Paulo City. The sample from the triatomine showed trypomastigote forms of Trypanosomatidae, which were inoculated in the peritoneum of Balb/c mice. The sample was then inoculated in Liver Infusion Tryptose medium and J774 cells for the molecular identification and characterization of the parasite. The Pm strain of T. cruzi was identified by isolation in axenic culture medium, and based on the morphology, cell infection, growth kinetics, and molecular characterization. RESULTS: After isolation, the protozoan was identified as T. cruzi. No parasites were detected in the peripheral blood of the animal, which can be a characteristic inherent to the strain of T. cruzi that was isolated. Cell invasion assays were performed in triplicate in the J774 cell line to confirm the invasive ability of the Pm strain and revealed amastigote forms of the parasite within macrophages. CONCLUSIONS: Our biological and molecular characterizations helped understand parasite-host interactions and their evolutionary history in context of the associations between vectors, ecotopes, hosts, and groups of the parasite.

Evaluation of natural foci of Panstrongylus megistus in a forest fragment in Porto Alegre, State of Rio Grande do Sul, Brazil

Introduction Panstrongylus megistus is commonly found in wild environments of the State of Rio Grande do Sul, Brazil. The aim of this study was to characterize the network of refuges used by triatomine in a forest fragment of Porto Alegre and to identify Trypanosoma cruzi infection, associated hosts and the epidemiological importance of both hosts and triatomines. Methods Techniques including the spool-and-line method and active searching (transects) were used to identify natural foci. Results The food source for each triatomine was determined using the precipitin test, and the infection of marsupials was determined by xenodiagnosis. A total of 33 adults (domestic environment) and 27 nymphs (wild environment) of P. megistus were found in addition to 43 Didelphis albiventris specimens. The infection rates of triatomine adults, triatomine nymphs and opossums with T. cruzi I were 64%, 73% and 69%, respectively. Birds, rodents and opossums were the main resources used by triatomine. Conclusions This work presents the first characterization of a natural focus of P. megistus in Rio Grande do Sul. The natural characteristics of this focus and its implication in the transmission of T. cruzi are discussed. .

Triatomines in dwellings and outbuildings in an endemic area of Chagas disease in northeastern Brazil / Triatomíneos no intra e peridomicílio de área endêmica de doença de Chagas no Nordeste do Brasil

INTRODUCTION: The present study identified the triatomines collected in intra and peri-domestic environments, observed the occurrence of Trypanosoma cruzi infection in triatomines and correlated this information with housing conditions and the fauna associated with the rural areas of the City of Itabaianinha, located in the State of Sergipe, Brazil. METHODS: Quarterly visits were conducted between March 2009 and March 2010, and the homes to be visited for the active search of insects were determined by random selection. In each housing unit, the insects were collected by a manual search with a metal clip and flashlight to inspect openings and cavities, with a collection time of one hour/home/individual. The Pirisa® dislodge chemical was used to force the insects to leave their ecotopes. Analysis of the intestinal contents of triatomines was performed in the laboratory to establish the presence of Trypanosomatidae. RESULTS: Of the 103 dwellings surveyed, 17.5% were infested with Panstrongylus megistus. The village of Mutuca exhibited the highest infestation rate (38.1%). All the villages with relevant infestation rates were situated in the northern area of the city. The highest percentage of vector infection was found in the village of Água Boa (56.5%). The rural dwellings were found to be primarily brick or wooden house with or without roughcast or plastered walls, and the outbuilding most frequently associated with triatomines was the chicken run. CONCLUSIONS: These results emphasise the need for broader vector control and surveillance and for educational campaigns in the context of the Chagas Disease Control Program.

INTRODUÇÃO: O presente trabalho teve como objetivo identificar os triatomíneos coletados no intra e peridomicílio, assim como verificar a ocorrência de infecção por Trypanosoma cruzi e correlacionar essas informações às condições habitacionais e à fauna associada na zona rural de Itabaianinha, Sergipe, Brasil. MÉTODOS: Visitas trimestrais foram realizadas entre março de 2009 e março de 2010, e as casas visitadas para a busca ativa de insetos foram determinadas por sorteio. Em cada unidade habitacional, os insetos foram capturados por coleta manual com pinça e lanterna para examinar aberturas e cavidades, com um tempo de coleta de uma hora/casa/indivíduo. O desalojador químico Pirisa® foi utilizado para forçar os insetos a abandonar seus ecótopos. A análise do conteúdo intestinal dos triatomíneos foi realizado no laboratório para estabelecer a presença de tripanosomatídeos. RESULTADOS: Em 103 unidades domiciliares examinadas, 17,5% estavam infestadas por triatomíneos da espécie Panstrongylus megistus. O Povoado Mutuca apresentou a mais elevada taxa de infestação das unidades domiciliares (38,1%). Todos os povoados que apresentaram índices de infestação relevantes estavam localizados na região norte do município. A maior percentagem de infecção desse vetor foi observada no Povoado Água Boa (56,5%). As habitações rurais observadas eram em sua maioria de tijolo ou madeira com as paredes rusticamente rebocadas ou sem reboco, e o anexo frequentemente associado ao triatomíneo foi o galinheiro. CONCLUSÕES: Os resultados obtidos ressaltam a necessidade de vigilância e controle vetorial mais abrangentes, bem como de campanhas educativas no contexto do PCDCh.

First report of Panstrongylus megistus sylvatic focus in municipality of Bambuí, state of Minas Gerais, Brazil

In 1943, the Center for the Study and Prophylaxis of Chagas Disease, Oswaldo Cruz Foundation, state of Minas Gerais (MG), was created in the municipality of Bambuí to carry out studies related to Chagas disease in the mid-western region of MG. Since that time, several investigations have been conducted to determine the natural habitat of triatomines, but Panstrongylus megistus colonies have never been found in this region. This paper records the first finding of a P. megistus sylvatic colony in 69 years of research. The characteristics of this ecotope and its implications for the epidemiology of Chagas disease are discussed.

Prevalence and intensity of infection, metacyclogenesis and nuclear phenotypes in Panstrongylus megistus (Burmeister, 1835) after ingestion of Trypanosoma cruzi (Chagas, 1909) II and subjection to heat shock / Prevalência e intensidade de infecção, metaciclogênese e fenótipos nucleares em Panstrongylus megistus (Burmeister, 1835) após ingestão de Trypanosoma cruzi (Chagas, 1909) II e choque de temperatura

This study aimed to contribute to our knowledge of the parasite-vector interaction associated with Trypanosoma cruzi (Chagas, 1909) infection in Panstrongylus megistus (Burmeister, 1835), an important vector of Chagas' disease in Brazil. The prevalence and intensity of T. cruzi infection, the incidence of metacyclogenesis and the frequency of nuclear phenotypes in Malpighian tubules were investigated in nymphs of P. megistus, reared at 28 °C and subjected to heat shock (40 °C, 1 hour) two days after infection with T. cruzi II (Y strain). Following the 45-day post-infection period, the frequency of epimastigotes was much higher than that of trypomastigotes in both heat-shocked and non-shocked insects, and the prevalence of infection was not altered by heat shock. Fewer epimastigotes and trypomastigotes were found in the infected insects subjected to the heat shock, indicating that the multiplication and metacyclogenesis of the parasites were affected by the stress. In infected specimens heat shock promoted an increased frequency of cell nuclei with heterochromatin decondensation, a cell survival response to stress, and did not affect insect survival. The effects of infection and heat shock, especially on the multiplication and metacyclogenesis of T. cruzi, and the observed resistance to heat shock developed by P. megistus nymphs are suggestive that they should be considered when adequate conditions for rearing these infected insects in the laboratory are pursued.(AU)

O presente estudo teve como objetivo contribuir para o conhecimento sobre a interação parasita-vetor associada à infecção por Trypanosoma cruzi (Chagas, 1909) em Panstrongylus megistus (Burmeister, 1835), importante vetor da doença de Chagas no Brasil. A prevalência e a intensidade da infecção por T. cruzi, a incidência de metaciclogênese e a frequência de fenótipos nucleares presentes em túbulos de Malpighi foram investigadas em ninfas de P. megistus criadas à temperatura de 28 °C e submetidas a choque térmico por 1 hora a 40 °C, dois dias após alimentação em camundongos infectados com T. cruzi II (linhagem Y). A análise realizada 45 dias pós-infecção revelou que tanto nos insetos submetidos ao choque térmico como nos respectivos controles a frequência de epimastigotos se apresentava muito maior do que a dos tripomastigotos; a prevalência da infecção não foi alterada pelo choque térmico. Menos epimastigotos e tripomastigotos foram encontrados nos insetos submetidos ao choque térmico, indicando que a multiplicação e a metaciclogênese dos parasitas possam ser afetadas com o estresse. Nos espécimes infectados, o choque térmico induziu aumento na frequência de núcleos com descompactação da heterocromatina, uma resposta de sobrevivência celular ao estresse, e não afetou a sobrevivência propriamente dita do inseto. Os efeitos da infecção e do choque térmico, especialmente sobre a multiplicação e a metaciclogênese de T. cruzi, e a resistência ao choque térmico desenvolvidos pelas ninfas de P. megistus são indicativos de que devam ser considerados quando se buscam condições adequadas de criação em laboratório de insetos infectados.(AU)

Prevalence and intensity of infection, metacyclogenesis and nuclear phenotypes in Panstrongylus megistus (Burmeister, 1835) after ingestion of Trypanosoma cruzi (Chagas, 1909) II and subjection to heat shock / Prevalência e intensidade de infecção, metaciclogênese e fenótipos nucleares em Panstrongylus megistus (Burmeister, 1835) após ingestão de Trypanosoma cruzi (Chagas, 1909) II e choque de temperatura

This study aimed to contribute to our knowledge of the parasite-vector interaction associated with Trypanosoma cruzi (Chagas, 1909) infection in Panstrongylus megistus (Burmeister, 1835), an important vector of Chagas' disease in Brazil. The prevalence and intensity of T. cruzi infection, the incidence of metacyclogenesis and the frequency of nuclear phenotypes in Malpighian tubules were investigated in nymphs of P. megistus, reared at 28 °C and subjected to heat shock (40 °C, 1 hour) two days after infection with T. cruzi II (Y strain). Following the 45-day post-infection period, the frequency of epimastigotes was much higher than that of trypomastigotes in both heat-shocked and non-shocked insects, and the prevalence of infection was not altered by heat shock. Fewer epimastigotes and trypomastigotes were found in the infected insects subjected to the heat shock, indicating that the multiplication and metacyclogenesis of the parasites were affected by the stress. In infected specimens heat shock promoted an increased frequency of cell nuclei with heterochromatin decondensation, a cell survival response to stress, and did not affect insect survival. The effects of infection and heat shock, especially on the multiplication and metacyclogenesis of T. cruzi, and the observed resistance to heat shock developed by P. megistus nymphs are suggestive that they should be considered when adequate conditions for rearing these infected insects in the laboratory are pursued.

O presente estudo teve como objetivo contribuir para o conhecimento sobre a interação parasita-vetor associada à infecção por Trypanosoma cruzi (Chagas, 1909) em Panstrongylus megistus (Burmeister, 1835), importante vetor da doença de Chagas no Brasil. A prevalência e a intensidade da infecção por T. cruzi, a incidência de metaciclogênese e a frequência de fenótipos nucleares presentes em túbulos de Malpighi foram investigadas em ninfas de P. megistus criadas à temperatura de 28 °C e submetidas a choque térmico por 1 hora a 40 °C, dois dias após alimentação em camundongos infectados com T. cruzi II (linhagem Y). A análise realizada 45 dias pós-infecção revelou que tanto nos insetos submetidos ao choque térmico como nos respectivos controles a frequência de epimastigotos se apresentava muito maior do que a dos tripomastigotos; a prevalência da infecção não foi alterada pelo choque térmico. Menos epimastigotos e tripomastigotos foram encontrados nos insetos submetidos ao choque térmico, indicando que a multiplicação e a metaciclogênese dos parasitas possam ser afetadas com o estresse. Nos espécimes infectados, o choque térmico induziu aumento na frequência de núcleos com descompactação da heterocromatina, uma resposta de sobrevivência celular ao estresse, e não afetou a sobrevivência propriamente dita do inseto. Os efeitos da infecção e do choque térmico, especialmente sobre a multiplicação e a metaciclogênese de T. cruzi, e a resistência ao choque térmico desenvolvidos pelas ninfas de P. megistus são indicativos de que devam ser considerados quando se buscam condições adequadas de criação em laboratório de insetos infectados.

Análise da fonte alimentar de Panstrongylus megistus (Hemiptera, Reduviidae, Triatominae) e sua atual importância como vetor do Trypanosoma cruzi, no Estado de Minas Gerais / Analysis on the food source of Panstrongylus megistus (Hemiptera, Reduviidae, Triatominae) and its present importance as a vector for Trypanosoma cruzi, in the State of Minas Gerais

INTRODUÇÃO: A pesquisa da fonte alimentar dos triatomíneos auxilia no conhecimento sobre a biologia destes insetos, inclusive para inferir-se a importância dos mesmos como transmissores do Trypanosoma cruzi ao homem. MÉTODOS: O presente estudo objetivou registrar, através da reação de precipitina, a fonte alimentar de triatomíneos provenientes de 54 municípios da região centro-oeste de Minas Gerais, assim como a infecção natural destes para flagelados semelhantes ao Trypanosoma cruzi. RESULTADOS: De julho de 2003 até março de 2007, foram avaliados 416 insetos, todos da espécie Panstrongylus megistus. Somando-se as ocorrências, as aves (70 por cento) e os humanos (22,5 por cento) constituíram as principais fontes sanguíneas. Encontrou-se 16 (3,8 por cento) insetos positivos para flagelados semelhantes ao Trypanosoma cruzi sendo que oito realizaram hematofagia no homem. CONCLUSÕES: Os resultados demonstram necessidade de acentuar a vigilância entomológica na região, visto que foi detectada a possibilidade de ocorrência de novos casos da doença de Chagas através da transmissão vetorial.

INTRODUCTION: Investigation of the food source of triatomines helps in understanding the biology of these insects, and also helps to infer their importance in transmitting Trypanosoma cruzi to humans. METHODS: The present study aimed to use the precipitin reaction to record the food source of triatomines from 54 municipalities in the central-western region of the State of Minas Gerais, as well as their natural infection by flagellates similar to Trypanosoma cruzi. RESULTS: From July 2003 to March 2007, 416 insects were evaluated, all from the species Panstrongylus megistus. Among all these occurrences, birds (70 percent) and humans (22.5 percent) were the major blood sources. Sixteen (3.8 percent) of the insects were found to be positive for flagellates similar to Trypanosoma cruzi, and eight performed hematophagia on humans. CONCLUSIONS: The results show the need to increase the entomological surveillance in this region, given that the possibility of new cases of Chagas disease occurring through vector transmission was detected.

Entomological surveillance of Chagas disease in Berilo municipality, Jequitinhonha Valley, State of Minas Gerais, Brazil / Vigilância Entomológica da doença de Chagas no município de Berilo, Vale do Jequitinhonha, Estado de Minas Gerais, Brasil

This study aimed to evaluate the Chagas Disease Control Program which has operated since 1982 in the municipality of Berilo in the Jequitinhonha Valley, Minas Gerais, Brazil, based on evaluation of 5,242 domiciliary units (DUs) and 7,807 outbuildings over an eight-year period of epidemiological surveillance implanted in 1997. A total of 391 triatomines (280 Panstrongylus megistus and 111 Triatoma pseudomaculata) were captured, indicating the continued predominance of the former species. However, Triatoma pseudomaculata is clearly becoming more important in this region, with intradomiciliary colonies being detected in recent years. Entomological parameters, such as dispersion (17 percent) and intradomiciliary infestation (0.15 percent) indices, are compatible with the results of the epidemiological surveillance. The majority of DUs were of construction type A (plaster over bricks) or C (plaster over adobe). Twenty-five percent of the inhabitants of the DUs infested by triatomines were reactive in ELISA, IHA and IIF tests for Trypanosoma cruzi antigens.

O objetivo deste estudo foi avaliar o Programa de Controle de doença de Chagas instalado desde 1982 no município de Berilo, Vale do Jequitinhonha, MG, Brasil, baseado na avaliação de 5.242 unidades domiciliares e 7.807 anexos após oito anos de implantação da vigilância epidemiológica que ocorreu em 1997. Um total de 391 triatomíneos (280 Panstrongylus megistus e 111 Triatoma pseudomaculata) foram capturados, indicando o contínuo predomínio da primeira espécie. No entanto, Triatoma pseudomaculata está claramente se tornando mais importante nesta região, com colônias intradomiciliares sendo detectadas recentemente. Parâmetros entomológicos, como os índices de dispersão (17 por cento) e infestação intradomiciliar (0,15 por cento), são compatíveis com a fase de vigilância epidemiológica. A maioria das UDs apresenta padrão de construção tipo A (tijolo com reboco) e C (adobe com reboco). Dentre os habitantes das unidades domiciliares infestadas por triatomíneos, 25 por cento apresentavam testes reativos na ELISA, HAI e IFI para antígenos de Trypanosoma cruzi.

Phenetic analysis of Panstrongylus megistus Burmeister, 1835 (Hemiptera: Reduviidae: Triatominae) in the State of Paraná-Brazil

Panstrongylus megistus is an important Chagas Disease vector and is said to be one of the species that might replace Triatoma infestans as the main vector of that disease in Brazil. The different degrees of P. megistus domiciliation in Brazil and its epidemiological relevance draw forth the need for the development of genetic studies that make it possible to analyze and understand the interchange of individual and gene fluxes among different populations. Thus, the present work aimed at studying the genetic variability of P. megistus in the State of Paraná - south of Brazil- and at comparing it with populations of the same species from five other states in Brazil (SP, MG, SC, RS, SE). In order to attain the proposed objective, 25 populations were studied using fifteen isoenzymatic systems (6PGD, G6PD, ME¹, ME², ICD, PGM, GPI, GOT¹, GOT², NP¹, NP², DIA, MPI, F, and MDH). The phenetic analysis allowed the individuation of 22 electromorphs and five zymodemes. The G6PD enzyme was the only polymorphic one presenting four electromorphs for the studied populations, all of them described for the State of Paraná-BR. The P. megistus populations from other states grouped with those from Paraná-BR, evidencing a low genetic variability in that species. Despite the existing geographic barriers, sub-samples - away from one another by at most 570km - were grouped in one and the same zymodeme. The epidemiological implications of such results are discussed in the present work.

Panstrongylus megistus é um importante vetor da Doença de Chagas e é apontado como uma das espécies com potencial para substituir Triatoma infestans como principal vetor desta doença no Brasil. Os diferentes graus de domiciliação por P. megistus - no Brasil - e sua importância epidemiológica evocam a necessidade de estudos com bases genéticas que possibilitem analisar e compreender os intercâmbios de indivíduos e os fluxos gênicos entre as distintas populações. Assim, o presente trabalho tem como objetivo estudar a variabilidade genética de P. megistus no Estado do Paraná e compará-los com populações da mesma espécie de cinco estados do Brasil (SP, MG, SC, RS, SE). Para atingir o objetivo proposto, 25 populações foram estudadas empregando quinze sistemas isoenzimáticos (6PGD, G6PD, ME¹, ME², ICD, PGM, GPI, GOT¹, GOT², NP¹, NP², DIA, MPI, FH e MDH). A análise fenética permitiu a individualização de 22 eletromorfos e quatro zimodemas. A enzima G6PD foi a única polimórfica que apresentou quatro eletromorfos para as populações estudadas, todas descritas para o Estado do Paraná. As populações de P. megistus procedentes dos outros estados agruparam-se com as do Paraná, demonstrando haver baixa variabilidade genética na espécie. Apesar das barreiras geográficas existentes, sub-amostras - distantes entre si por até 570 km - ficaram reunidas num mesmo zimodema. As implicações epidemiológicas destes resultados são discutidas no presente trabalho.

Colonização intradomiciliar de Panstrongylus megistus (Hemiptera, Reduviidae, Triatominae) em São José do Cerrito, SC: primeiro relato / Colonization by Panstrongylus megistus (Hemiptera, Reduviidae, Triatominae) inside homes in São José do Cerrito, SC: first report

Em resposta a uma denúncia da existência de triatomíneos em uma cabana de pesca as margens do Rio Caveiras no município de São José do Cerrito-SC, foi feita a investigação na cabana e em outros ecótopos vizinhos ao achado inicial. Foram encontrados 15 exemplares de Panstrongylus megistus sendo que nenhum deles encontrava-se infectado. O local do ecótopo é visitado ocasionalmente por capivaras, gambás, tatus e ratos.

In response to complaints of the presence of triatomines in a fishing hut on the banks of the Caveiras river, in the municipality of São José do Cerrito, State of Santa Catarina, an investigation was conducted in this hut and in other ecotopes neighboring the initial finding. Fifteen specimens of Panstrongylus megistus were found and none of them were infected. The locality of this ecotope is visited occasionally by capybaras, opossums, armadillos and rats.

Experimentally induced heat- and cold-shock tolerance in adult Panstrongylus megistus (Burmeister) (Hemiptera, Reduviidae)

The survival rate of domestic male and female adult Panstrongylus megistus was studied after sequential heat and cold shocks in order to investigate shock tolerance compared to that previously reported for nymphs. Sequential shocks were such that a milder shock (0°C, 5°C, 35°C, or 40°C for 1 h) preceded a severe one (0°C or 40°C for 12 h), separated by intervals of 8, 18, 24, and 72 h at 28°C (control temperature). The preliminary thermal shock induced tolerance to the more severe one, although tolerance intensity depended on the initial shock temperature and the interval between treatments. Despite the observed tolerance, the survival rate for insects subjected to both shocks decreased when compared to that of individuals subjected to a single mild shock. When tolerance differed with sex, females showed greater values than males. In contrast to the response detected in nymphs, for which higher heat tolerance values were sustained for intervals of up to 24 h (preliminary shock, 35ºC) or even longer (preliminary shock, 40ºC) between sequential shocks, significant values were verified in adults only for shock intervals of up to 8 h (preliminary shock, 40ºC). While findings for nymphs exhibited considerable cold-shock tolerance under conditions in which preliminary shocks were given at 5ºC or 0ºC and the periods between shocks were up to 72 h long, the adults were shown to be capable of acquiring a substancial tolerance response to a more severe cold shock only when the preliminary shock was given at 0ºC and shock interval surpassed 18 h. It is assumed that the mechanisms involved in the cellular protection of P. megistus under sequential temperature shocks (heat shock protein action?) may loose effectiveness with insect development.

A taxa de sobrevivência de alados domiciliares machos e fêmeas de Panstrongylus megistus foi analisada, após choques seqüenciais quentes e frios, a fim de investigar aquisição de termotolerância em comparação a dados já reportados para ninfas. Os insetos foram submetidos a choques térmicos seqüenciais, sendo que um choque mais suave (0°C, 5°C, 35°C ou 40°C por 1 h) precedeu o choque mais severo (0°C ou 40°C por 12 h). Estes foram separados por intervalos de 8, 18, 24 e 72 h a 28°C (temperatura-controle). Demonstrou-se que o choque térmico preliminar pode induzir tolerância ao mais severo, embora a intensidade de tolerância seja dependente da temperatura inicial do choque e do intervalo entre os tratamentos. Apesar da tolerância observada, a taxa de sobrevivência diminuiu em insetos submetidos a ambos os choques quando comparados àqueles espécimes submetidos a um único choque suave. Quando a tolerância diferiu com o sexo, as fêmeas apresentaram tolerância maior. Diferentemente da resposta observada em ninfas, para as quais a tolerância a choques quentes se estende até quando o período entre os choques é de 24 h (choque inicial a 35ºC) ou mais (choque inicial a 40ºC), taxa expressiva de tolerância nos adultos foi verificada apenas em condições de até 8 h de intervalo entre os choques, sendo o choque inicial dado a 40ºC. Também diferindo do que acontece às ninfas, cuja tolerância ao choque frio se expressa em todas as condições semelhantemente estudadas, nos adultos observou-se expressiva tolerância ao choque frio apenas quando o choque inicial foi dado a 0ºC e o tempo entre choques seguidos ultrapassou 18 h. Presume-se que em P. megistus os mecanismos que desempenham papel na proteção celular a choques seqüenciais de temperatura (proteínas de choque?) possam perder a eficácia com o desenvolvimento do inseto.

Distribuição de Panstrongylus megistus (Hemiptera, Reduviidae, Triatominae) no estado do Maranhão, Brasil

Based on a survey on the presence of P. megistus in several localities of Maranhão State, performed by the National Foundation of Health, from 1982 to 1995, the distribution of this species is shown. The capture of the adults and nymphs in the domestic environment was the basic method employed. The process of capture started at the rear and finished at the front of the human dwellings, and the surroundings as patio, back yard, garden, harbouring chickens, were inspected afterwards. All the specimens collected were identified. An effort was made to try to detect Trypa-nosoma from the intestinal content of some bugs. Maranhão is made up of 136 municipalities and the survey covered 87 of them. Panstrongylus megistus was in 14 municipal districts which belonging to the savana zone (cerrados) in the southern portion of the State. In total, 1,632 specimens of P. megistus were captured and 277 were examined resulting in the rate of 1.1% of infection with Trypanosoma cruzi. São João dos Patos (22.4%), Pastos Bons (15%), São Raimundo das Mangabeiras (14.5%), Mirador (14.3%), Riachão (8.3%) and Loreto (6.2%) were the municipal districts in which the presence of P. megistus was more common. For the moment, P. megistus is found only in south-east and south of Maranhão. Judging by the current distribution this specie penetrated through the "cerrados" from of the neighbouring states of Goiás, Tocantins and Piauí.

Apresenta-se a distribuição de Panstrongylus megistus no Estado do Maranhão, com base nos dados do inquérito triatomínico realizado pela Fundação Nacional de Saúde, de 1982 a 1995. O método básico utilizado foi a captura de adultos e ninfas nos ambientes peri e intradomiciliares. Os trabalhos de coleta dentro das casas começavam pelos cômodos dos fundos, passando de um aposento para o outro, até a frente. Na parte externa das casas foram inspecionados pátio, quintal, jardim e anexos - galinheiro, chiqueiro, estábulo, curral etc. Todos os exemplares encontrados eram capturados, identificados e, quando possível, examinado o conteúdo intestinal para detecção de Trypanosoma. O estudo envolveu 87 dos 136 municípios em que se divide geograficamente o Maranhão. O Panstrongylus megistus encontrava-se confinado em 14 municípios pertencentes à zona dos cerrados que caracterizam a porção mais meridional do Estado. Dos 1.632 exemplares capturados 277 foram examinados, resultando no índice global de infecção por Trypanosoma tipo cruzi de 1,1%. Os municípios que apresentaram maior quantidade de espécimens capturados foram São João dos Patos (22,4%), Pastos Bons (15%), São Raimundo das Mangabeiras (14,5%), Mirador (14,3%), Riachão (8,3%) e Loreto (6,2%). Atualmente, o P. megistus restringe a sua área de ocorrência às regiões sudeste e sul do Maranhão. A julgar por este padrão de distribuição, presume-se que esta espécie penetrou no território maranhense através dos estados do Piauí, Goiás ou Tocantins, utilizando os cerrados como rota.

Distribuição de Panstrongylus megistus (Hemiptera, Reduviidae, Triatominae) no estado do Maranhão, Brasil

Based on a survey on the presence of P. megistus in several localities of Maranhão State, performed by the National Foundation of Health, from 1982 to 1995, the distribution of this species is shown. The capture of the adults and nymphs in the domestic environment was the basic method employed. The process of capture started at the rear and finished at the front of the human dwellings, and the surroundings as patio, back yard, garden, harbouring chickens, were inspected afterwards. All the specimens collected were identified. An effort was made to try to detect Trypa-nosoma from the intestinal content of some bugs. Maranhão is made up of 136 municipalities and the survey covered 87 of them. Panstrongylus megistus was in 14 municipal districts which belonging to the savana zone (cerrados) in the southern portion of the State. In total, 1,632 specimens of P. megistus were captured and 277 were examined resulting in the rate of 1.1% of infection with Trypanosoma cruzi. São João dos Patos (22.4%), Pastos Bons (15%), São Raimundo das Mangabeiras (14.5%), Mirador (14.3%), Riachão (8.3%) and Loreto (6.2%) were the municipal districts in which the presence of P. megistus was more common. For the moment, P. megistus is found only in south-east and south of Maranhão. Judging by the current distribution this specie penetrated through the "cerrados" from of the neighbouring states of Goiás, Tocantins and Piauí.

Apresenta-se a distribuição de Panstrongylus megistus no Estado do Maranhão, com base nos dados do inquérito triatomínico realizado pela Fundação Nacional de Saúde, de 1982 a 1995. O método básico utilizado foi a captura de adultos e ninfas nos ambientes peri e intradomiciliares. Os trabalhos de coleta dentro das casas começavam pelos cômodos dos fundos, passando de um aposento para o outro, até a frente. Na parte externa das casas foram inspecionados pátio, quintal, jardim e anexos - galinheiro, chiqueiro, estábulo, curral etc. Todos os exemplares encontrados eram capturados, identificados e, quando possível, examinado o conteúdo intestinal para detecção de Trypanosoma. O estudo envolveu 87 dos 136 municípios em que se divide geograficamente o Maranhão. O Panstrongylus megistus encontrava-se confinado em 14 municípios pertencentes à zona dos cerrados que caracterizam a porção mais meridional do Estado. Dos 1.632 exemplares capturados 277 foram examinados, resultando no índice global de infecção por Trypanosoma tipo cruzi de 1,1%. Os municípios que apresentaram maior quantidade de espécimens capturados foram São João dos Patos (22,4%), Pastos Bons (15%), São Raimundo das Mangabeiras (14,5%), Mirador (14,3%), Riachão (8,3%) e Loreto (6,2%). Atualmente, o P. megistus restringe a sua área de ocorrência às regiões sudeste e sul do Maranhão. A julgar por este padrão de distribuição, presume-se que esta espécie penetrou no território maranhense através dos estados do Piauí, Goiás ou Tocantins, utilizando os cerrados como rota.