Chagas vectors Panstrongylus chinai (Del Ponte, 1929) and Panstrongylus howardi (Neiva, 1911): chromatic forms or true species?

BACKGROUND: Chagas disease is a parasitic infection transmitted by "kissing bugs" (Hemiptera: Reduviidae: Triatominae) that has a huge economic impact in Latin American countries. The vector species with the upmost epidemiological importance in Ecuador are Rhodnius ecuadoriensis (Lent & Leon, 1958) and Triatoma dimidiata (Latreille, 1811). However, other species such as Panstrongylus howardi (Neiva, 1911) and Panstrongylus chinai (Del Ponte, 1929) act as secondary vectors due to their growing adaptation to domestic structures and their ability to transmit the parasite to humans. The latter two taxa are distributed in two different regions, they are allopatric and differ mainly by their general color. Their relative morphological similarity led some authors to suspect that P. chinai is a melanic form of P. howardi. METHODS: The present study explored this question using different approaches: antennal phenotype; geometric morphometrics of heads, wings and eggs; cytogenetics; molecular genetics; experimental crosses; and ecological niche modeling. RESULTS: The antennal morphology, geometric morphometrics of head and wing shape and cytogenetic analysis were unable to show distinct differences between the two taxa. However, geometric morphometrics of the eggs, molecular genetics, ecological niche modeling and experimental crosses including chromosomal analyses of the F1 hybrids, in addition to their coloration and current distribution support the hypothesis that P. chinai and P. howardi are separate species. CONCLUSIONS: Based on the evidence provided here, P. howardi and P. chinai should not be synonymized. They represent two valid, closely related species.

Genetic data support speciation between Panstrongylus howardi and Panstrongylus chinai, vectors of Chagas disease in Ecuador.

Limited genetic data are currently available for three vectors of Chagas disease in Ecuador, Panstrongylus howardi, P. chinai, and P. rufotuberculatus. Previously regarded as mainly sylvatic, these species have been poorly studied. Recently, they have been more frequently reported in domiciles and peridomiciles and are now considered true secondary vectors of Chagas disease in a country where an estimated 200,000 people are infected by Trypanosoma cruzi, a causative agent of this disease. In order to fill this gap, we obtained DNA for sequencing from 53 insects belonging to these three species and mainly sampled from the two Ecuadorian provinces of Loja and Manabí. We used six mitochondrial loci (COI, COII, ND4, CytB, 16S, and 12S) and two nuclear ones (ITS2 and 18S). We interpreted the phylogenetic trees built with single and concatenated data through maximum likelihood, Bayesian Markov chain Monte Carlo, and maximum parsimony methods. We provide evidence that P. chinai and P. howardi are indeed two supported species closely related and derived from a common ancestor. Additionally, the phylogenetic position of P. rufotuberculatus was confirmed as being distant from P. chinai and P. howardi and clustered with Triatoma dimidiata, a species belonging to the Northern American Triatoma clade.

Genetic diversification of Panstrongylus geniculatus (Reduviidae: Triatominae) in northern South America.

Triatomines are the vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Although Triatoma and Rhodnius are the most-studied vector genera, other triatomines, such as Panstrongylus, also transmit T. cruzi, creating new epidemiological scenarios. Panstrongylus has at least 13 reported species but there is limited information about its intraspecific genetic variation and patterns of diversification. Here, we begin to fill this gap by studying populations of P. geniculatus from Colombia and Venezuela and including other epidemiologically important species from the region. We examined the pattern of diversification of P. geniculatus in Colombia using mitochondrial and nuclear ribosomal data. Genetic diversity and differentiation were calculated within and among populations of P. geniculatus. Moreover, we constructed maximum likelihood and Bayesian inference phylogenies and haplotype networks using P. geniculatus and other species from the genus (P. megistus, P. lignarius, P. lutzi, P. tupynambai, P. chinai, P. rufotuberculatus and P. howardi). Using a coalescence framework, we also dated the P. geniculatus lineages. The total evidence tree showed that P. geniculatus is a monophyletic species, with four clades that are concordant with its geographic distribution and are partly explained by the Andes orogeny. However, other factors, including anthropogenic and eco-epidemiological effects must be investigated to explain the existence of recent geographic P. geniculatus lineages. The epidemiological dynamics in structured vector populations, such as those found here, warrant further investigation. Extending our knowledge of P. geniculatus is necessary for the accurate development of effective strategies for the control of Chagas disease vectors.

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

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.

Entomological triatomine indicators in the State of Rio Grande do Norte, Brazil. / Indicadores entomológicos de triatomíneos no Estado do Rio Grande do Norte, Brasil.

This study aimed to describe the main entomological triatomine-related indicators in the western mesoregion of Rio Grande do Norte. This is a descriptive cross-sectional retrospective study developed on a historical analysis of information on the triatomine capture carried out by the Chagas Disease Control Program, from 2008 to 2013. Five species were captured, of which the Triatoma brasiliensis and Triatoma pseudomaculata, by occupying the domestic and peridomestic environment, sequentially, and Panstrongylus lutzi by the highest rate of natural infection. A prevalence of nymphs among the captured specimens, a higher triatominal density in the peridomicile, infestation, colonization and natural infection rates of 5.6%, 49.6% and 0.8%, respectively, a significant difference in the distribution of specimens between the municipalities investigated and lack of declining infestation and colonization rates between 2009 and 2012 was observed. Findings suggest the need for continuous surveillance, facilitated by the association between field teams and communities, with emphasis on the proposal of health education for the recognition and notification of triatomines by the population.

Objetivou-se descrever os principais indicadores entomológicos relacionados aos triatomíneos na mesorregião Oeste do Rio Grande do Norte. Trata-se de estudo descritivo, transversal e retrospectivo, desenvolvido com base em análise histórica de informações sobre a captura de triatomíneos realizada pelo Programa de Controle de doença de Chagas, no período de 2008 a 2013. Foram capturadas cinco espécies, das quais se destacaram a Triatoma brasiliensis e a Triatoma pseudomaculata, pela ocupação do ambiente domiciliar e peridomiciliar, sequencialmente, e a Panstrongylus lutzi, pelo maior índice de infecção natural. Observou-se prevalência de ninfas dentre os exemplares capturados, maior densidade triatomínica no peridomicílio, índices de infestação, colonização e infecção natural de 5,6%, 49,6% e 0,8%, respectivamente, diferença significativa na distribuição de espécimes entre os municípios investigados e ausência de declínio dos índices de infestação e colonização entre os anos de 2009 e 2012. Os achados sugerem a necessidade de vigilância contínua, possibilitada pela associação entre as equipes de campo e as comunidades, com ênfase na proposta de educação em saúde para o reconhecimento e notificação dos triatomíneos pela população.

Confirmation of the occurrence of Panstrongylus rufotuberculatus (Champion, 1899) in the state of Acre, Western Amazon.

INTRODUCTION: This study aimed to confirm the occurrence of Panstrongylus rufotuberculatus in the state of Acre, Brazil. METHODS: The four specimens of P. rufotuberculatus were obtained from the entomological collection of the Zoobotanical Park of the Federal University of Acre (UFAC). RESULTS: Confirmation of the occurrence of this species in the state of Acre increases the number of species already registered, from nine to ten. CONCLUSIONS: The necessity to develop further studies was verified, especially with the domiciliary process of P. rufotuberculatus, resulting in tracing prophylactic measures against the vector transmission of Trypanosoma cruzi.

Indicadores entomológicos de triatomíneos no Estado do Rio Grande do Norte, Brasil / Entomological triatomine indicators in the State of Rio Grande do Norte, Brazil

Resumo Objetivou-se descrever os principais indicadores entomológicos relacionados aos triatomíneos na mesorregião Oeste do Rio Grande do Norte. Trata-se de estudo descritivo, transversal e retrospectivo, desenvolvido com base em análise histórica de informações sobre a captura de triatomíneos realizada pelo Programa de Controle de doença de Chagas, no período de 2008 a 2013. Foram capturadas cinco espécies, das quais se destacaram a Triatoma brasiliensis e a Triatoma pseudomaculata, pela ocupação do ambiente domiciliar e peridomiciliar, sequencialmente, e a Panstrongylus lutzi, pelo maior índice de infecção natural. Observou-se prevalência de ninfas dentre os exemplares capturados, maior densidade triatomínica no peridomicílio, índices de infestação, colonização e infecção natural de 5,6%, 49,6% e 0,8%, respectivamente, diferença significativa na distribuição de espécimes entre os municípios investigados e ausência de declínio dos índices de infestação e colonização entre os anos de 2009 e 2012. Os achados sugerem a necessidade de vigilância contínua, possibilitada pela associação entre as equipes de campo e as comunidades, com ênfase na proposta de educação em saúde para o reconhecimento e notificação dos triatomíneos pela população.

Abstract This study aimed to describe the main entomological triatomine-related indicators in the western mesoregion of Rio Grande do Norte. This is a descriptive cross-sectional retrospective study developed on a historical analysis of information on the triatomine capture carried out by the Chagas Disease Control Program, from 2008 to 2013. Five species were captured, of which the Triatoma brasiliensis and Triatoma pseudomaculata, by occupying the domestic and peridomestic environment, sequentially, and Panstrongylus lutzi by the highest rate of natural infection. A prevalence of nymphs among the captured specimens, a higher triatominal density in the peridomicile, infestation, colonization and natural infection rates of 5.6%, 49.6% and 0.8%, respectively, a significant difference in the distribution of specimens between the municipalities investigated and lack of declining infestation and colonization rates between 2009 and 2012 was observed. Findings suggest the need for continuous surveillance, facilitated by the association between field teams and communities, with emphasis on the proposal of health education for the recognition and notification of triatomines by the population.

First report of Panstrongylus lignarius (Walker, 1873) (Hemiptera: Reduviidae: Triatominae) in the State of Acre, Brazil.

INTRODUCTION: This communication reports the first occurrence of Panstrongylus lignarius in the State of Acre, Brazil. METHODS: A specimen of P. lignarius was collected from a residence in a rural area of the municipality of Rio Branco, Acre, Western Amazon. RESULTS: This new report of P. lignarius extends the distribution of this species to eight Brazilian states, and also increases the number of species of Triatominae described from the state of Acre from nine to ten. CONCLUSIONS: The occurrence of P. lignarius deserves attention, since this species has the potential for domiciliation and transmitting Trypanosoma cruzi.

Identification Key for the Chagas Disease Vectors of Five Brazilian States, Based on Cytogenetic Data.

Chagas disease is a public health problem caused by the protozoan Trypanosoma cruzi that affects about 8 million people worldwide. The main form of transmission of T. cruzi is vectorial, through triatomines feces contaminated with the parasite. All species are considered as potential vectors of T. cruzi. The main identification keys of these vectors are based only on morphological characters. However, there are very similar or even same species (cryptic species) that may lead to wrong classification of the vectors. Therefore, we developed an identification key using cytogenetic data, to aid and help the correct classification of triatomines. From the cytogenetic characters, identification keys were created for the five Brazilian states (Alagoas, Amapá, Ceará, Roraima, and Santa Catarina). These data are important because the correct classification of triatomines helps directly the activity of the vector control programs.

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.

Confirmation of the occurrence of Panstrongylus rufotuberculatus (Champion, 1899) in the state of Acre, Western Amazon

Abstract: INTRODUCTION This study aimed to confirm the occurrence of Panstrongylus rufotuberculatus in the state of Acre, Brazil. METHODS The four specimens of P. rufotuberculatus were obtained from the entomological collection of the Zoobotanical Park of the Federal University of Acre (UFAC). RESULTS Confirmation of the occurrence of this species in the state of Acre increases the number of species already registered, from nine to ten. CONCLUSIONS The necessity to develop further studies was verified, especially with the domiciliary process of P. rufotuberculatus, resulting in tracing prophylactic measures against the vector transmission of Trypanosoma cruzi.

First report of Panstrongylus lignarius (Walker, 1873) (Hemiptera: Reduviidae: Triatominae) in the State of Acre, Brazil

Abstract INTRODUCTION: This communication reports the first occurrence of Panstrongylus lignarius in the State of Acre, Brazil. METHODS: A specimen of P. lignarius was collected from a residence in a rural area of the municipality of Rio Branco, Acre, Western Amazon. RESULTS: This new report of P. lignarius extends the distribution of this species to eight Brazilian states, and also increases the number of species of Triatominae described from the state of Acre from nine to ten. CONCLUSIONS: The occurrence of P. lignarius deserves attention, since this species has the potential for domiciliation and transmitting Trypanosoma cruzi.

Genetic variability of Panstrongylus geniculatus (Reduviidae: Triatominae) in the Metropolitan District of Caracas, Venezuela.

Panstrongylus geniculatus has become the most frequently registered vector of Chagas disease in the metropolitan area of Caracas, Venezuela. This triatomine species has invaded urban areas in recent years and has been implicated in multiple oral outbreaks of Chagas disease in the region. The study of genetic variability and spatial structure in P. geniculatus populations can provide information about possible events of domiciliation and aid intervention programs against triatomine species rapidly adapting to urban ecotopes. We sequenced a region of the cytochrome-b gene in 114 specimens of P. geniculatus from the Metropolitan District of Caracas and assessed patterns of gene flow and phylogenetic relationships among these individuals. A total of 29 haplotypes were detected in the two sampled municipalities, Sucre and Libertador. Though high genetic connectivity was observed between the municipalities (FST = 0.10796; Nm = 11.20), subtle genetic structuring was also observed in particular geographic sub regions. Based on neutrality tests and the observed allele-frequency distribution, the Panstrongylus geniculatus population appears to be expanding and adapting to different microhabitats present in the study area. Our findings affirm the capacity of this insect to adapt to different environments and emphasize its principal role in the epidemiology of Chagas disease in northern Venezuela.

The modern morphometric approach to identify eggs of Triatominae.

BACKGROUND: Egg morphometrics in the Triatominae has proved to be informative for distinguishing tribes or genera, and has been based generally on traditional morphometrics. However, more resolution is required, allowing species or even population recognition, because the presence of eggs in the domicile could be related to the species ability to colonize human dwellings, suggesting its importance as a vector. RESULTS: We explored the resolution of modern morphometric methods to distinguish not only tribes and genera, but also species or geographic populations in some important Triatominae. Four species were considered, representing two tribes and three genera: Panstrongylus chinai and P. howardi, Triatoma carrioni and Rhodnius ecuadoriensis. Within R. ecuadoriensis, two geographical populations of Ecuador were compared. For these comparisons, we selected the most suitable day of egg development, as well as the possible best position of the egg for data capture. The shape of the eggs in the Triatominae does not offer true anatomical landmarks as the ones used in landmark-based morphometrics, except for the egg cap, especially in eggs with an evident "neck", such as those of the Rhodniini. To capture the operculum shape variation, we used the landmark- and semilandmark-based method. The results obtained from the metric properties of the operculum were compared with the ones provided by the simple contour of the whole egg, as analyzed by the Elliptic Fourier Analysis. Clear differences could be disclosed between the genera, between the species - among which two very close species (P. chinai and P. howardi), as well as between two allopatric, conspecific populations. The whole egg contour (including the operculum) produced reclassification scores much more satisfactory than the ones obtained using the operculum only. CONCLUSIONS: We propose the outline-based approach as the most convenient characterization tool to identify unknown eggs at the species or population levels.

Risks associated with dispersive nocturnal flights of sylvatic Triatominae to artificial lights in a model house in the northeastern plains of Colombia.

BACKGROUND: Control initiatives and continuous surveillance of vector-borne transmission have proved to be effective measures for diminishing the incidence of Chagas disease in endemic countries. However, the active dispersal of infected sylvatic adult triatomines by flight represents one of the main obstacles to eliminating domestic transmission. METHODS: In order to determine the risk that active dispersal of sylvatic adult triatomines represents in Colombian northeastern plains, we quantified the distribution and abundance of triatomines in palm trees (primarily Attalea butyracea) using live bait traps. Directional light traps were used to estimate the frequency of sylvatic triatomine dispersal and their possible origin. Finally, the effect of environmental parameters and artificial light sources on the take-off of sylvatic Rhodnius prolixus was evaluated in field experiments. RESULTS: R. prolixus was found in 90 % of the palm trees that densely aggregated toward the northern portion of the study area. R. prolixus, and three other sylvatic triatomine species were found to actively disperse and were attracted to the directional light traps (Triatoma maculata, Panstrongylus geniculatus and Psammolestes arthuri). Temperature, relative humidity, wind speed and night luminosity did not affect the active dispersal of the triatomines which is higher the first two hours after sunset. Artificial lights from houses at 60 and 110 m played a key role in the directionality of the R. prolixus take-offs. Trypanosoma cruzi was isolated from R. prolixus, T. maculata and P. geniculatus and was genotyped as T. cruzi I, III and IV. CONCLUSIONS: Our results highlight the potential risk in Colombian northeastern plains of actively dispersing sylvatic triatomines and their role in the domestic introduction of Discrete Typing Units of T. cruzi associated to sylvatic foci of Chagas disease transmission.

Genes encoding defensins of important Chagas disease vectors used for phylogenetic studies.

Insects possess both cellular and humoral immune responses. The latter makes them capable to recognize and control invading pathogens after synthesis of a variety of small proteins, also known as antimicrobial peptides. Defensins, cysteine-rich cationic peptides with major activity against Gram-positive bacteria, are one ubiquitous class of antimicrobial peptides, widely distributed in different animal and plant taxa. Regarding triatomines in each of the so far analyzed species, various defensin gene isoforms have been identified. In the present study, these genes were sequenced and used as a molecular marker for phylogenetic analysis. Considering the vectors of Chagas disease the authors are reporting for the first time the presence of these genes in Triatoma sordida (Stål, 1859), Rhodnius nasutus (Stål, 1859), and Panstrongylus megistus (Burmeister, 1835). Members of the Triatoma brasiliensis species complex were included into the study to verify the genetic variability within these taxa. Mainly in their mature peptide, the deduced defensin amino acid sequences were highly conserved. In the dendrogram based on defensin encoding nucleotide, sequences the Triatoma Def3/4 genes were separated from the rest. In the dendrogram based on deduced amino acid sequences the Triatoma Def2/3/4 together with Rhodnius DefA/B pre-propeptides were separated from the rest. In the sub-branches of both the DNA and amino acid dendrograms, the genus Triatoma was separated from the genus Rhodnius as well as from P. megistus.

Triatominae survey (Hemiptera: Reduviidae: Triatominae) in the south-central region of the state of Bahia, Brazil between 2008 and 2013.

Triatomine surveillance in rural areas, artificial ecotypes, and natural ecotopes of the cities of Caturama, Ibipitanga, Macaúbas, and Seabra in the south-central region of the Brazilian state of Bahia was carried out between 2008 and 2013. Natural infection by Trypanosoma cruzi was evaluated in the specimens collected to monitor vectors of Chagas disease. A total of 1,357 specimens were collected, and four species were identified: Triatoma sordida (83%), Triatoma lenti (16.4%), Triatoma pseudomaculata (0.5%), and Panstrongylus geniculatus (0.1%). Triatoma sordida was found in four cities, only 0.7% in intradomiciliary environments. Triatoma lenti was found only in Macaúbas; 8.5% were found in intradomiciliary environments, 88.3% in peridomiciliary environments, and 3.1% in sylvatic environments. Natural infection by T. cruzi was 0.5% for T. sordida and 3.1% T. lenti. All of these cases were found in peridomiciliary environments of Macaúbas. As the results show, triatomines were found in intradomiciliary environments in three cities that were surveyed in the south-central region of the state of Bahia. Thus, an epidemiologic survey should be performed to avoid the risk of transmission to the population.