First report of Rhodnius montenegrensis (Hemiptera, Reduviidae, Triatominae) in Amazonas, Brazil

Abstract INTRODUCTION: Triatomines are hematophagous insects of epidemiological importance because they are vectors of Chagas disease. We present here the first report of Rhodnius montenegrensis in Amazonas, Brazil. METHODS: Triatomines were collected from Attalea butyracea palm trees in the municipality of Guajará. RESULTS: Two adult female R. montenegrensis specimens were identified. CONCLUSIONS: The present study confirms that the number of triatomine species within the Amazon has increased from 10 to 11, and the number of Brazilian states with R. montenegrensis has increased from two to three.

Differentiation of Rhodnius neglectus and Rhodnius prolixus (Hemiptera: Reduviidae: Triatominae) by multiple parameters

Abstract Introduction: The genus Rhodnius in the subfamily Triatominae comprises 20 species, which can transmit Trypanosoma cruzi and Trypanosoma rangeli. Due to the development of molecular techniques, Triatominae species can now be characterized by mitochondrial and nuclear markers, making it possible to verify and/or correct the existing data on these species. The results achieved in this study provide a more detailed and accurate differentiation of the Rhodnius species, helping the establishment of a more appropriate classification. Methods: Data collection was performed by DNA analysis, morphological and morphometric studies to distinguish four populations of R. neglectus and four of R. prolixus. Phylogenetic data were compared to morphological and morphometric data. Results: The analysis of Cytb fragments suggests that the four colonies designated to Rhodnius neglectus as well as those of R. prolixus were correctly identified. Conclusions: The morphological characters observed in the specimens of the colonies originally identified as R. prolixus and R. neglectus, such as the presence or absence of collar in the eggs, the patterns of the median process of the pygophore, and anterolateral angle, are consistent with the species. Geometric morphometrics also show an intraspecific variability in R. prolixus.

Occurrence of triatomines in an urban residential complex in the municipality of Rio Branco, Acre, South-Western Amazon

Abstract INTRODUCTION: This study describes the occurrence of triatomines, and their positivity for trypanosomatids, in a residential complex in Rio Branco, Acre, Brazil. METHODS: Triatomines were collected through direct capture in a home environment. Positivity analysis for trypanosomatids was performed by PCR assays. RESULTS Collected insects consisted of 31 Rhodnius robustus, 4 Rhodnius montenegrensis, and 1 Panstrongylus geniculatus specimens. All were adults, with no presence of domiciliation, and with an infection rate of 30.6%. CONCLUSIONS Future studies are recommended in other locations of Rio Branco in order to develop a georeference database of the occurrence of triatomines in urban areas.

First report of Rhodnius neglectus (Hemiptera, Reduviidae, Triatominae) from the State of Acre, Brazil, and the Brazilian Western Amazon Region

Abstract INTRODUCTION This communication reports the occurrence of Rhodnius neglectus in the State of Acre, Brazil. METHODS An adult male R. neglectus specimen was collected from the Catuaba Experimental Reserve, which is located in the municipality of Senador Guiomard. RESULTS This increases the number of triatomine species reported from the State of Acre to eight and is also the first report of R. neglectus from the Brazilian Western Amazon Region. CONCLUSIONS The occurrence of R. neglectus is alarming because even though the species is wild, it can invade and colonize human dwellings and peridomiciles, thereby increasing Chagas disease transmission.

Rhodnius stali: new vector infected by Trypanosoma rangeli (Kinetoplastida, Trypanosomatidae)

Abstract INTRODUCTION Rhodnius stali infection by Trypanosoma rangeli is reported in this study for the first time. METHODS The triatomines were collected from the campus of the Federal University of Acre in Rio Branco, Acre, Brazil. The identification of T. rangeli was confirmed by multiplex polymerase chain reaction. RESULTS The examinations of two specimens revealed R. stali infection by the epimastigote forms of T. rangeli. CONCLUSIONS The encounter of R. stali infected by T. rangeli generates an alert for the state of Acre, since the simultaneous presence with Trypanosoma cruzi can make the differential diagnosis of Chagas disease difficult.

First report of Rhodnius montenegrensis (Hemiptera, Reduviidae, Triatominae) in the State of Acre, Brazil

This paper reports, for the first time, the presence of Rhodnius montenegrensis in the State of Acre, Brazil.

Ciclo biológico de Rhodnius stali Lent, Jurberg e Galvão, 1993 e Rhodnius pictipes Stal, 1872 (Hemiptera, Reduviidae, Triatominae) em condições de Laboratório / Biological cycle of Rhodnius stali Lent, Jurberg & Galvão, 1993 and Rhodnius pictipes Stål, 1872 (Hemiptera, Reduviidae, Triatominae) in laboratory conditions

Passado mais de um século da sua descoberta a doença de Chagas (DC) outripanossomíase Americana é uma enfermidade para a qual ainda não existe vacina ou fármaco eficaz para o seu tratamento. Desta forma, o controle vetorial ainda permanece sendo uma das melhores estratégias. Assim,conhecer os parâmetros biológicos das espécies silvestres que possam atuar como vetores nas áreas endêmicas são primordiais para o fornecimento de informações que nortearão as ações da Secretária de Vigilância em saúde(SVS) no controle vetorial. Rhodnius stali Lent, Jurberg and Galvão vetor da doença de Chagas, domiciliado na região do Alto Beni, Bolívia é uma espécie com a biologia pouco conhecida. Com o objetivo de ampliar o conhecimento acerca de sua biologia, observamos parâmetros de seu ciclo de vida, nos estádios de ninfas, comparando-os com Rhodnius pictipes Stal, 1872, espécie morfologicamente semelhante e filogeneticamente próxima. Os seguintes parâmetros foram observados: tempo de eclosão dos ovos, ciclo de biológico de ovo-adulto (em machos e fêmeas separadamente), taxa de mortalidade,primeiro repasto sanguíneo realizado e volume de sangue ingerido pelas ninfas. De maneira geral observou-se que as fêmeas de Rhodnius stali possui um ciclo de vida mais longo do que Rhodnius pictipes e, em ambas as espécies, o tempo entre a eclosão dos ovos até a fase adulta é menor em fêmeas. Curiosamente para R.stali, que é sabiamente capaz de colonizar domicílios, foi observada uma taxa de mortalidade das ninfas mais alta queem R.pictipes, algo inesperado para a espécie que coloniza estruturas artificiais e foi observada em ambiente artificial. Para Rhodnius stali o primeiro repasto sanguíneo ocorreu, em média, quatro dias mais tarde do que em R.pictipes Deve-se levar em consideração, que antes da descrição R.stali, osdados obtidos sobre a biologia de R.pictipes devem ser considerados com reserva, já que ambas poderiam ser facilmente confundidas...

Over a century after its discovery, Chagas disease (CD) or AmericanTrypanosomiasis is an incurable illness without vaccine or effective drug forthe treatment. Being so, vector control remains one of the best strategies.Therefore, knowing the biological parameters of sylvatic species that might actas vectors in endemic areas is primordial for the provision of information thatwill guide the actions of the Secretaria de Vigilância em Saúde (SVS) onvector control. Rhodnius stali Lent, Jurberg and Galvão, a vector of CD,domiciliated on Alto Beni region, Bolivia, is a species with poorly knownbiology. Aiming to broaden the knowledge about its biology, its life cycleparameters have been observed on nymphal stages and compared with R.pictipes Stal, 1872, a morphologically and phylogenetically similar species.The following parameters were observed: egg eclosion time, life cycle fromegg to adult (separately for males and females), mortality rate, first bloodmeal, and volume of blood ingested by the nymphs. Generally, females ofboth species have shorter life cycles than males, whereas those of R. staliusually live longer than R. pictipes. Curiously, a higher nymphal mortality ratewas found in R. stali, which is unexpected for a domiciliated species capableof colonizing artificial structures. The first blood meal of R. stali occurred fourdays later than in R. pictipes in average. It is important to mention that dataobtained about the biology of R. pictipes prior to the description of R. stalimust be considered with caution, because both species could easily beconfused...

Rhodnius barretti, a new species of Triatominae (Hemiptera: Reduviidae) from western Amazonia

Rhodnius barretti , a new triatomine species, is described based on adult specimens collected in rainforest environments within the Napo ecoregion of western Amazonia (Colombia and Ecuador). R. barretti resembles Rhodnius robustus s.l. , but mitochondrial cytochrome b gene sequences reveal that it is a strongly divergent member of the “robustus lineage”, i.e., basal to the clade encompassing Rhodnius nasutus , Rhodnius neglectus , Rhodnius prolixus and five members of the R. robustus species complex. Morphometric analyses also reveal consistent divergence from R. robustus s.l. , including head and, as previously shown, wing shape and the length ratios of some anatomical structures. R. barretti occurs, often at high densities, in Attalea butyracea and Oenocarpus bataua palms. It is strikingly aggressive and adults may invade houses flying from peridomestic palms. R. barretti must therefore be regarded as a potential Trypanosoma cruzi vector in the Napo ecoregion, where Chagas disease is endemic.

Natural infection of triatomines (Hemiptera: Reduviidae) by trypanosomatids in two different environments in the municipality of Ouro Preto do Oeste, State of Rondônia, Brazil / Infecção natural de triatomíneos (Hemiptera: Reduviidae) por tripanosomatídeos em dois ambientes distintos no município de Ouro Preto do Oeste, Estado de Rondônia, Brasil

INTRODUCTION: This study analyzed the occurrence and the contamination of triatomines by trypanosomatids in Orbignya speciosa (babassu) specimens in the State of Rondônia, Brazil, in two different environments (pasture and woods). METHODS: Capture of triatomines on babassus and microscopic search for trypanosomatids in their digestive tube were carried out. RESULTS: Four hundred ninety-four (494) specimens were captured (Rhodnius prolixus and R.robustus), of which 35.6% of the triatomines were positive for trypanosomatids. CONCLUSIONS: The high index of natural infection along with the abundance of triatomines points out to the necessity to create an epidemiological surveillance system to monitor vector-borne transmission and deepen the studies on the ecology of such vectors in the Amazon.

INTRODUÇÃO: O estudo analisou a ocorrência e o índice de contaminação por tripanosomatídeos de triatomíneos em Orbynia speciosa no Estado de Rondônia, Brasil, em 2 ambientes (pastagem e floresta). MÉTODOS: Captura em palmeiras e esfregaços do conteúdo do tubo digestivo dos triatomíneos analisados por microscopia óptica. RESULTADOS: Capturaram-se 494 espécimes (Rhodnius prolixus e R. robustus), sendo que 35,6% dos triatomíneos estavam positivos para tripanosomatídeos. CONCLUSÕES: O elevado índice de infecção natural, aliados à abundância de triatomíneos, mostram a necessidade de se criar um sistema de vigilância epidemiológica para monitorar a transmissão vetorial e aprofundar estudos sobre a ecologia destes vetores na Amazônia.

Biologia comparativa e comportamento alimentar de Rhodnius neglectus e Rhodnius robustus (Triatominae) sob condições de laboratório / Comparative biology and feeding behavior of Rhodnius neglectus and Rhodnius robustus (Triatominae) under laboratory conditions

INTRODUÇÃO: A competência vetorial de triatomíneos é determinada a partir de estudos sobre biologia e comportamento alimentar em condições de campo e/ou laboratório. Fatores como número de picadas, quantidade de sangue ingerido e tempo de defecação têm implicações na transmissão de tripanosomatídeos. Parâmetros biológicos e comportamentais de Rhodnius neglectus e R. robustus foram comparados experimentalmente para estimar diferenças no potencial de transmissão de tripanosomatídeos. MÉTODOS: Os triatomíneos foram observados diariamente para determinar o período de desenvolvimento ninfal, mortalidade, detecção da fonte alimentar, número de picadas, tempo do repasto sanguíneo, quantidade de sangue ingerido, tempo entre o final do repasto e a primeira defecação e frequência de defecação. RESULTADOS: Apesar do período ninfal de R. neglectus (156,4 ± 25,05d) ter sido menor que o de R. robustus (204,7 ± 13,22d), a mortalidade foi similar entre as espécies (63,8 e 65%, respectivamente). R. robustus e R. neglectus detectaram rapidamente a fonte alimentar, especialmente no primeiro estádio (2,5 e 1,6min, respectivamente). Apesar do tempo de repasto sanguíneo ter sido similar entre as espécies, R. robustus ingeriu em média uma maior quantidade de sangue em todos os estádios, com maiores valores para as ninfas V. As ninfas de R. neglectus picaram mais vezes as fontes alimentares, defecaram mais rápido e mais frequentemente que as de R. robustus. CONCLUSÕES: Sob as condições de laboratório usadas, R. neglectus possui um maior potencial para transmissão de Trypanosoma cruzi e T. rangeli que R. robustus, atributo que deve ser avaliado em infecções experimentais.

INTRODUCTION: The vector competence of triatomine insects is determined by studying their biology and feeding behavior under field and/or laboratory conditions. Factors including the number of bites, the amount of blood ingested and defecation time have implications for trypanosome transmission. The biological and behavioral parameters of Rhodnius neglectus and R. robustus were compared under experimental conditions to estimate differences in the potential transmission of trypanosomes. METHODS: The insects were observed daily to determine the period of nymphal development, mortality, detection of food source, number of bites, time of blood meal intake, amount of blood ingested, time elapsed between the end of the meal and the first defecation and the frequency of defecation. RESULTS: Although the nymphal development of R. neglectus (156.4 ± 25.05d) was lower than that of R. robustus (204.7 ± 13.22d), the mortality between species was similar (63.8 and 65% respectively).R. robustus and R. neglectus quickly located the food source, especially in the first instar (2.5 and 1.6 min, respectively). Although the time of blood meal intake was similar between the species, R. robustus ingested a larger amount of blood on average at all stages and exhibited higher values for the fifth instar. Nymphs of R. neglectus bit more frequently, and they defecated faster and more often than those of R. robustus. CONCLUSIONS: Under laboratory conditions, R. neglectus has a greater potential for transmission of Trypanosoma cruzi and T. rangeli than does R. robustus, an attribute that should be further evaluated in experimental infections.

Ocorrência de triatomíneos em ambientes silvestres e domiciliares do município de Manaus, Estado do Amazonas / Occurrences of triatomines in wild and domestic environments in the municipality of Manaus, State of Amazonas

A análise da distribuição de triatomíneos é essencial para a formulação de estratégias de controle da doença de Chagas na Região Amazônica. Neste trabalho, apresentam-se os resultados de capturas realizadas em ambientes silvestres e artificiais, em localidades rurais e urbanas de Manaus, Amazonas. Dos 115 triatomíneos coletados, 85 (73,9 por cento) são da espécie Rhodnius pictipes, 25 (21,7 por cento) de Rhodnius robustus e cinco (4,4 por cento) de Panstrongylus geniculatus. A taxa de infecção natural por flagelados foi de 5,9 por cento para Rhodnius pictipes e 8 por cento para Rhodnius robustus. Nenhum exemplar de Panstrongylus geniculatus estava infectado. Todos os exemplares infectados eram oriundos de fragmentos de matas da zona urbana. Verificou-se que 106 (92,2 por cento) triatomíneos foram coletados no ambiente silvestre e nove (7,8 por cento) nas unidades domiciliares pela busca ativa. O gênero Rhodnius predominou nitidamente no ambiente silvestre. Os exemplares de Panstrongylus geniculatus, todos adultos, foram coletados no intradomicílio. Não foram encontrados indícios de colonização domiciliar por triatomíneos.

Analysis of the distribution of triatomines is essential for formulating control strategies for Chagas disease in the Amazon region. In this paper, the results from trapping in wild and artificial environments in rural and urban localities in Manaus, Amazonas, are presented. Out of the 115 triatomines collected, 85 (73.9 percent) were of the species Rhodnius pictipes, 25 (21.7 percent) of Rhodnius robustus and five (4.4 percent) of Panstrongylus geniculatus. The rate of natural infection by flagellates was 5.9 percent for Rhodnius pictipes and 8 percent for Rhodnius robustus. None of the specimens of Panstrongylus geniculatus were infected. All of the infected specimens were from forest fragments in the urban zone. It was found that 106 insects (92.2 percent) were collected from the forest environment and nine (7.8 percent) in households, by means of the active search. The genus Rhodnius clearly predominated in the wild environment. The specimens of Panstrongylus geniculatus (all adults) were collected inside homes. There were no signs of domestic colonization by triatomines.

Ecological niche modelling and differentiation between Rhodnius neglectus Lent, 1954 and Rhodnius nasutus Stål, 1859 (Hemiptera: Reduviidae: Triatominae) in Brazil

Ecological niche modelling was used to predict the potential geographical distribution of Rhodnius nasutus Stål and Rhodnius neglectus Lent, in Brazil and to investigate the niche divergence between these morphologically similar triatomine species. The distribution of R. neglectus covered mainly the cerrado of Central Brazil, but the prediction maps also revealed its occurrence in transitional areas within the caatinga, Pantanal and Amazon biomes. The potential distribution of R. nasutus covered the Northeastern Region of Brazil in the semi-arid caatinga and the Maranhão babaçu forests. Clear ecological niche differences between these species were observed. R. nasutus occurred more in warmer and drier areas than R. neglectus. In the principal component analysis PC1 was correlated with altitude and temperature (mainly temperature in the coldest and driest months) and PC2 with vegetation index and precipitation. The prediction maps support potential areas of co-occurrence for these species in the Maranhão babaçu forests and in caatinga/cerrado transitional areas, mainly in state of Piaui. Entomologists engaged in Chagas disease vector surveillance should be aware that R. neglectus and R. nasutus can occur in the same localities of Northeastern Brazil. Thus, the identification of bugs in these areas should be improved by applying morphometrical and/or molecular methods.

Comparative descriptions of eggs from three species of Rhodnius (Hemiptera: Reduviidae: Triatominae)

The authors describe and compare the morphological and ultrastructural characteristics of eggs from the three most recent described species of the genus Rhodnius Stål, 1859, which have not previously been studied. These species are Rhodnius colombiensis (Mejia, Galvão & Jurberg 1999), Rhodnius milesi (Carcavallo, Rocha, Galvão & Jurberg 2001) and Rhodnius stali (Lent, Jurberg & Galvão 1993). The results revealed that there are similarities in the exochorial architecture of optical microscopy and scanning electron microscopy; these include the predominance of hexagonal cells that are common to all Rhodnius species and variable degrees of lateral flattening, which is common not only to species of this genus, but also to the Rhodniini tribe. Differences in overall colour, the presence of a collar in R. milesi, a longitudinal bevel in R. stali and the precise length of R. colombiensis can be useful distinguishing features. As a result of this study, the key for egg identification proposed by Barata in 1981 can be updated.

Quantification of the genetic change in the transition of Rhodnius pallescens Barber, 1932 (Hemiptera: Reduviidae) from field to laboratory

Previous studies have reported genetic differences between wild-caught sylvatic, domestic and laboratory pop-ulations of several Triatominae species. The differences between sylvatic and laboratory colonies parallel are similar to the differences observed between sylvatic and domestic populations. Laboratory colonies are frequently used as references for field populations, but the consequences of founder events on the genetic makeup of laboratory or domestic populations are rarely quantified. Our goal was to quantify the genetic change in Rhodnius pallescens populations artificially submitted to founder effects via laboratory colonization. We compared the genetic makeup of two sylvatic populations and their laboratory descendants using a panel of 10 microsatellite markers. Both sylvatic populations were initially collected from palm trees, but the colonies differed in the number of founder insects and amount of time kept in the laboratory. We evaluated allelic polymorphism, differences between expected and observed heterozygosity, estimates of population differentiation (Fst) and inbreeding (Fis, Fit) and cluster analyses based on Nei's distances. We found a unique genetic structure for each sample population, with significant differentiation between the field insects and each of the laboratory generations. These analyses showed strong founder effects and showed that genetic drift had led to a genetic equilibrium over several generations of isolation. Our results suggest that laboratory colonies of R. pallescens have a different genetic structure than their wild relatives and similar processes likely affect other Triatominae laboratory stocks.

Rhodnius zeledoni sp. nov. afim de Rhodnius paraensis Sherlock, Guitton & Miles, 1977 (Hemiptera, Reduviidae, Triatominae) / Rhodnius zeledoni sp. nov. afim de Rhodnius paraensis Sherlock, Guitton & Miles, 1977 (Hemiptera, Reduviidae, Triatominae)

A new species of Rhodnius is described and illustrated from a male specimen from northeastern Brazil. The specimen was found died and dried. This species can be distinguished from its similar congener R. paraensis Sherlock, Guitton & Miles by the greater size, the general aspect of the color of the body, by the uniform color of the legs, different proportions between the morphological structures of the head and the segments of the rostrum; also, in the male genitalia by the aspect of median process of pygophore, dorsal phallotheca plate and phallotheca process.

Uma nova espécie de Rhodnius é descrita e ilustrada baseada em um exemplar macho do nordeste brasileiro. O espécime foi encontrado morto e ressecado. Esta espécie pode ser separada da espécie afim, R. paraensis Sherlock, Guitton & Miles, pelo seu maior tamanho, pelo aspecto geral de coloração do corpo, pela cor uniforme das pernas, pelas diferentes proporções entre as estruturas morfológicas da cabeça e dos segmentos do rostro; ainda, na genitália masculina, pelo aspecto do processo mediano do pigóforo, do falosoma e de seu processo.

Reassessing the entomological investigation around the first autochthonous case of Chagas disease in Western Brazilian Amazon

In 1979, the first autochthonous case of Chagas disease in the Western Brazilian Amazon was reported and an entomological survey was carried out around it. Specimens of Rhodnius pictipes and Rhodnius robustus were collected in intradomicile and sylvatic ecotopes. Adult bugs were infected with trypanosomatids. Invasion of houses by triatomines was demonstrated and the presence of infected bugs inside dwellings was associated with the possibility of vector-borne Chagas disease. Continuous entomological surveillance employing additional taxonomic tools is needed in the Brazilian Amazon in order to better understand the dynamics of house invasion by sylvatic triatomines and the risk of Trypanosoma cruzi infection transmission.

Ecological aspects of Rhodnius nasutus Stål, 1859 (Hemiptera: Reduviidae: Triatominae) in palms of the Chapada do Araripe in Ceará, Brazil

The aim of this work is to present aspects related to the ecology of Rhodnius nasutus Stål, 1859 in palms from Chapada do Araripe in Ceará, Brazil. The following five species of palms were investigated: babaçu (Attalea speciosa), buriti (Mauritia flexuosa), carnaúba (Copernicia prunifera), catolé (Syagrus oleracea) and macaúba-barriguda (Acrocomia intumescens). Fifth palms were dissected (10 specimens for each species). The overall infestation index was 86 percent, with a total of 521 triatomines collected. The Trypanosoma cruzi Chagas, 1909 Index was 16.8 percent and two insects presented mixed infection with Trypanosoma rangeli Tejera, 1920. A precipitin test showed that R. nasutus from palms of Chapada do Araripe are associated with opossum and bird although other possible bloodmeals were observed. Our results showing a high index of infestation of the palms as well as T. cruzi infection, the association of R. nasutus with the most diverse species of palms and proximity of these palms to houses demonstrate the importance of this area for sylvatic T. cruzi transmission and suggest the need for epidemiological surveillance in the region of the Chapada do Araripe.

Levantamento da fauna de Triatominae (Hemiptera: Reduviidae) em ambiente domiciliar e infecção natural por Trypanosomatidae no Estado de Mato Grosso do Sul / Survey of Triatominae (Hemiptera: Reduviidae) fauna in domestic environments and natural infection by Trypanosomatidae in the State of Mato Grosso do Sul

Entre 2000 a 2004, foi realizado levantamento da fauna de Triatominae (Hemiptera: Reduviidae) e exame de infecção natural por Trypanosomatidae, no Estado de Mato Grosso do Sul. Um total de 13.671 espécimes foram capturados. Na análise faunística das espécies capturadas, Triatoma sordida foi caracterizada como muito abundante, muito freqüente, constante e dominante. Os índices de infecção natural para Trypanosoma cruzi apresentaram os valores de 3,2 por cento para Panstrongylus geniculatus, 0,6 por cento para Rhodnius neglectus e 0,1 por cento para Triatoma sordida, apesar do Estado de Mato Grosso do Sul apresentar-se livre da transmissão vetorial endêmica.

Between 2000 and 2004, a survey of Triatominae fauna (Hemiptera: Reduviidae) and examination of natural infection caused by Trypanosomatidae in the State of Mato Grosso do Sul, Brazil, was conducted. A total of 13,671 specimens were collected. Through fauna analysis on the insects that were caught, Triatoma sordida was characterized as very abundant, very frequent, constant and dominant. The rates of natural infection with Trypanosoma cruzi were 3.2 percent for Panstrongylus geniculatus, 0.6 percent for Rhodnius neglectus and 0.1 percent for Triatoma sordida. Nevertheless, the State of Mato Grosso do Sul is free from endemic vector transmission.

Chromosome variability in the Chagas disease vector Rhodnius pallescens (Hemiptera, Reduviidae, Rhodniini)

Rhodnius pallescens is the main vector of Trypanosoma cruzi in Panama and one of the most relevant secondary vectors in Colombia. Despite the importance of this species, there is limited knowledge about the genetic variability along its geographical distribution. In order to evaluate the degree of karyotype variability we analyzed the meiotic behavior and banding pattern of the chromosomes of 112 males of R. pallescens coming from different regions of Colombia and Panama. Using the C-banding technique we identified two chromosomal patterns or cytotypes characterized by differences in the amount, size and distribution of constitutive heterochromatic regions in the chromosome complement (2n = 20 autosomes plus XY in males). The individuals can be easily classified in each cytotype by the analysis of the chromosomes during first meiotic prophase. The frequencies of the cytotypes are variable according to the geographic origin of the populations. This chromosomal divergence together with morphological data supports the existence of three genetically different populations of R. pallescens and provides new information to understand the distribution dynamics of this species.

Triatomines (Hemiptera, Reduviidae) prevalent in the northwest of Peru: species with epidemiological vectorial capacity

The development of strategies for the adequate control of the vector transmission of Chagas disease depends on the availability of updated data on the triatomine species present in each region, their geographical distribution, natural infections by Trypanosoma cruzi and/or T. rangeli, eco-biological characteristics and synanthropic behavioral tendencies. This paper summarizes and updates current information, available in previously published reports and obtained by the authors our own field and laboratory studies, mainly in northwest of Peru. Three triatomine species exhibit a strong synanthropic behavior and vector capacity, being present in domestic and peridomestic environments, sometimes showing high infestation rates: Rhodnius ecuadoriensis, Panstrongylus herreri and Triatoma carrioni The three species should be given continuous attention by Peruvian public health authorities. P. chinai and P. rufotuberculatus are bugs with increasing potential in their role as vectors according to their demonstrated synanthropic tendency, wide distribution and trophic eclecticism. Thus far we do not have a scientific explanation for the apparent absence ofT. dimidiata from previously reported geographic distributions in Peru. It is recommended, in the Peruvian northeastern Amazon region, the development of field studies on species of the genus Rhodnius, as well as of other triatominae, to evaluate their present Trypanosomatidae vector capacity.

El desarrollo de estrategias adecuadas para el control de la transmisión vectorial de la Enfermedad de Chagas depende: de la disponibilidad de datos actualizados de las especies de triatominos presentes en cada región, de su distribución geográfica, infección natural por Trypanosoma cruzi ylo T. rangeli, características eco-biológicas y tendencias de comportamiento sinantrópico. Este trabajo resume y actualiza la información disponible en la literatura y aquella obtenida en nuestros estudios de campo y de laboratorio desarrollados en los últimos años por los autores, predominantemente, en la región Nor-Occidental del Perú. El resultado de esas observaciones es la detección de que, tres especies de triatominos presentan un importante comportamiento sinantrópico y capacidad vectorial, ocupando ambientes intradomiciliares y peridomiciliares: Rhodnius ecuadoriensis, Panstrongylus herreri y Triatoma carrioni. Las tres especies deben recibir constante atención por parte de las autoridades de Salud Pública Peruana. P. chinai y P rufotuberculatus tienen potencial creciente en su papel de vectores, por la comprobada tendencia sinantrópica, distribución geográfica y eclecticismo trófico. Se desconocen las causas de la aparente ausencia actual de Triatoma dimidiata, dada su presencia constatada anteriormente en el Perú. Se recomienda que en la región Nor-Oriental Amazónica Peruana se realicen en forma urgente estudios sobre las especies del genero Rhodnius y de otros triatominos que permitan evaluar la real capacidad vectorial de los Trypano-somatideos.