Molecular and cytogenetic evidence for sibling species in the Chagas disease vector Triatoma maculata.

Triatoma maculata (Hemiptera, Reduviidae, Triatominae) occurs across dry-to-semiarid ecoregions of northern South America, where it transmits Trypanosoma cruzi, causative agent of Chagas disease. Using 207 field-caught specimens from throughout the species' range, mitochondrial(mt) DNA sequence data, and cytogenetics, we investigated inter-population genetic diversity and the phylogenetic affinities of T. maculata. Mitochondrial DNA sequence analyses (cytb and nd4) disclosed a monophyletic T. maculata clade encompassing three distinct geographic groups: Roraima formation (Guiana shield), Orinoco basin, and Magdalena basin (trans-Andean). Between-group cytb distances (11.0-12.8%) were larger than the ~7.5% expected for sister Triatoma species; the most recent common ancestor of these T. maculata groups may date back to the late Miocene. C-heterochromatin distribution and the sex-chromosome location of 45S ribosomal DNA clusters both distinguished Roraima bugs from Orinoco and Magdalena specimens. Cytb genealogies reinforced that T. maculata is not sister to Triatoma pseudomaculata and probably represents an early (middle-late Miocene) offshoot of the 'South American Triatomini lineage'. In sum, we report extensive genetic diversity and deep phylogeographic structuring in T. maculata, suggesting that it may consist of a complex of at least three sibling taxa. These findings have implications for the systematics, population biology, and perhaps medical relevance of T. maculata sensu lato.

Influence of blood meal source on the biological parameters of Triatoma pallidipennis (Heteroptera: Reduviidae) from Mexico.

Chagas disease is one of the most important vector-borne diseases in Latin America, including Mexico. Triatoma pallidipennis (Stål) (Hemiptera: Reduviidae) is a Mexican triatomine vector commonly associated with different hosts. The influence of six blood meals (rabbits, rats, mice, dogs, cats and chickens) on six biological parameters of the biology of T. pallidipennis was evaluated. A significant difference was found in the period of egg-to-adult development between the five mammalian feeds (mean 195 days) and the chicken feed (221 days). The probability of survival was significantly lower in the chicken cohort (0.285). The total number of blood meals to moult from the first instar to the adult stage was the highest in the chicken cohort (10-15). This cohort had the significantly highest rate of females at the end cycle. The mean number of eggs laid per female and the egg eclosion rate were similar among the six food sources. Most results seemed to be influenced by the higher nutritional quality of the mammalian blood compared to the bird's blood and the increased energy expenditure required for the digestion of bird blood. These results clearly show that T. pallidipennis, unlike other triatomine species, has a high reproductive capacity when feeding on different hosts.

High chromosomal mobility of rDNA clusters in holocentric chromosomes of Triatominae, vectors of Chagas disease (Hemiptera-Reduviidae).

The subfamily Triatominae (Hemiptera-Reduviidae) includes more than 150 blood-sucking species, potential vectors of the protozoan Trypanosoma cruzi, causative agent of Chagas disease. A distinctive cytogenetic characteristic of this group is the presence of extremely stable chromosome numbers. Unexpectedly, the analyses of the chromosomal location of ribosomal gene clusters and other repetitive sequences place Triatominae as a significantly diverse hemipteran subfamily. Here, we advance the understanding of Triatominae chromosomal evolution through the analysis of the 45S rDNA cluster chromosomal location in 92 Triatominae species. We found the 45S rDNA clusters in one to four loci per haploid genome with different chromosomal patterns: On one or two autosomes, on one, two or three sex chromosomes, on the X chromosome plus one to three autosomes. The movement of 45S rDNA clusters is discussed in an evolutionary context. Our results illustrate that rDNA mobility has been relatively common in the past and in recent evolutionary history of the group. The high frequency of rDNA patterns involving autosomes and sex chromosomes among closely related species could affect genetic recombination and the viability of hybrid populations, which suggests that the mobility of rDNA clusters could be a driver of species diversification.

Genetic diversity in a restricted-dispersal kissing bug: The centre-periphery hypothesis halfway.

The centre-periphery hypothesis (CPH) postulates that populations close to the centre of a species distribution will exhibit higher genetic diversity and lower genetic differentiation than populations located at the edge of the distribution. The centre of a species' distribution might represent an optimum for the environmental factors influencing the species absolute fitness and, therefore, genetic diversity. In species with wide distribution, the geographical variation of biotic and abiotic variables is crucial to understand the underlying mechanisms of the CPH. We evaluated the CPH and specifically tested which environmental variables better explained the patterns of genetic diversity in the kissing bug Mepraia spinolai, one of the main wild vectors of Chagas disease in southern South America, distributed across three Mediterranean climatic ecoregions in Chile. We analysed 2380 neutral single nucleotide polymorphisms to estimate genetic diversity. Mean winter temperature, mean summer temperature, vegetation cover, population abundance, proportion of winged individuals and female abdomen area were measured for each kissing bug population to construct a model. Lower genetic diversity was detected in populations at the edge of the distribution compared to those in the centre. However, genetic differentiation was not higher in the periphery. Genetic diversity was related to climatic and biological variables; there was a positive relationship with mean winter temperature and a negative association with mean summer temperature and body size. These results partially support the CPH and identify biotic (abdomen area) and abiotic (winter/summer temperatures) factors that would affect genetic diversity in this restricted-dispersal species of epidemiological relevance.

Seroprevalence of Chagas disease in rural communities at Campinas do Piauí city, Brazil.

OBJECTIVES: This manuscript aimed to evaluate the seroprevalence of Chagas's disease in the population of rural communities at Campinas do Piauí city, State of Piauí, Brazil. METHODS: The techniques of the indirect immunofluorescence reaction and enzyme-linked immunosorbent assay were used to detect reagent samples for Chagas disease and estimate its prevalence in the rural population. Blood samples were collected on filter paper through digital and venipuncture. Blood samples with reactive or indeterminate results were re-evaluated and subjected to the test by ELISA. RESULTS: In total, 763 blood samples were analysed from 161 residences of 18 rural communities, collected in residents aged between 2 and 92 years. In the indirect immunofluorescence reaction technique, 44 (5.8%) of the results were positive, being 40 (5.2%) confirmed by the enzyme-linked immunosorbent assay. Among the communities surveyed, we observed reactive cases in 15 of them, these cases being distributed, according to the age group, as follows: 1 case from 0 to 10 years; 13 cases from 11 to 60 years old; and 30 cases over 61 years. CONCLUSION: The results indicate that Chagas's disease remains with active transmission in the Campinas do Piaui city according to the occurrence of a case in a resident under 10 years of age. The region is endemic for Chagas's disease, as observed by the high prevalence of positive cases.

OBJECTIFS: Ce manuscrit visait à évaluer la séroprévalence de la maladie de Chagas dans la population des communautés rurales de la ville de Campinas do Piauí, état de Piauí, au Brésil. MÉTHODES: Les techniques de la réaction d'immunofluorescence indirecte et ELISA ont été utilisées pour détecter des échantillons réagissant pour la maladie de Chagas et estimer sa prévalence dans la population rurale. Des échantillons de sang ont été collectés sur papier filtre par ponction digitale et veineuse. Les échantillons de sang avec des résultats positifs ou indéterminés ont été réévalués et soumis au test ELISA. RÉSULTATS: Au total, 763 échantillons de sang ont été analysés dans 161 résidences de 18 communautés rurales, prélevés chez des résidents âgés de 2 à 92 ans. Dans la technique de la réaction d'immunofluorescence indirecte, 44 (5,8%) des résultats étaient positifs, dont 40 (5,2%) confirmés par le test ELISA. Parmi les communautés enquêtées, nous avons observé des cas réactifs dans 15 d'entre eux, ces cas se répartissant, selon la tranche d'âge, comme suit: 1 cas chez les 0 à 10 ans, 13 cas chez les 11 à 60 ans, 30 cas chez des plus de 61 ans. CONCLUSION: Les résultats indiquent que la maladie de Chagas maintient une transmission active dans la ville de Campinas do Piauí avec la survenue d'un cas chez un résident de moins de 10 ans. La région est endémique pour la maladie de Chagas, comme en témoigne la forte prévalence des cas positifs.

Rhodnius spp. are differentiated based on the peptide/protein profile by matrix-assisted laser desorption/ionization mass spectrometry and chemometric tools.

Triatominae are hematophagous insects involved in the transmission of Chagas disease. Among the 19 genera of the subfamily, those with the highest epidemiological importance regarding the dissemination of Trypanosoma cruzi are Panstrongylus, Rhodnius, and Triatoma. Of these three genera, Rhodnius presents the greatest difficulties for specific identification. Thus, there is a need to overcome the difficulties in identifying phenotypes of similar species of this genus. In the present study, the MALDI-TOF MS methodology was used to identify 12 Rhodnius species, among the 21 admitted. The MALDI-TOF MS methodology allowed specific characterization through the identification of peptides and proteins, starting from four different methods of extraction: (A) acetonitrile/formic acid (ACN/AF), (B) acetonitrile/trifluoroacetic acid (ACN/TFA), (C) isopropyl/formic acid (IPA/AF), and (D) methanol/formic acid (MeOH/AF), and four types of MALDI-TOF matrices: α-cyano-4-hydroxycinnamic acid (CHCA), sinapic acid (SA), 6-aza-2-thiothymine (ATT), and 2,6-dihydroxyacetophenone (DHAP). The experiments were performed by combining the four solvents and four matrices to select the best MALDI extraction/matrix. The application of the MALDI-TOF MS technique, through the digital mass spectrometry approach combined with chemometric tools, such as partial least squares-discriminant analysis (PLS-DA), was able to discriminate 12 species of Rhodnius genus, which are difficult to identify using morphological characteristics. Thus, in view of the results obtained, the methodology described in the present article can be applied with speed and efficiency for the discrimination of Triatominae species. Graphical Abstract.

Pattern of climate connectivity and equivalent niche of Triatominae species of the Phyllosoma complex.

The Phyllosoma complex is a Triatominae (Hemiptera: Reduviidae) group of medical importance involved in Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) transmission. Most of the members of this group are endemic and sympatric species with distribution in Mexico and the southern U.S.A. We employed MaxEnt to construct ecological niche models of nine species of Triatominae to test three hypothesis: (a) whether species with a broad climatic niche breadth occupy a broader geographical range than species with a narrow climatic breadth, (b) whether species with broad distribution present high degree of climatic fragmentation/isolation, which was tested through landscape metrics; and (c) whether the species share the same climatic niche space (niche conservatism) considered through an equivalence test implemented in ENMtools. Overall, our results suggest that the geographical distribution of this complex is influenced mainly by temperature seasonality where all suitable areas are places of current and potential transmission of T. cruzi. Niche breadth in the Phyllosoma complex is associated with the geographical distribution range, and the geographical range affects the climatic connectivity. We found no strong evidence of niche climatic divergence in members of this complex. We discuss the epidemiological implications of these results.

Oral Transmission of Trypanosoma cruzi, Brazilian Amazon.

In the Brazilian Amazon, the suspected source of infection in an outbreak of acute Chagas disease involving 10 patients was Euterpe oleracea (açaí berry) juice. Patient blood and juice samples contained Trypanosoma cruzi TcIV, indicating oral transmission of the Chagas disease agent.

The cost of being a killer's accomplice: Trypanosoma cruzi impairs the fitness of kissing bugs.

Relatively little is known about the fitness effects and life history trade-offs in medically important parasites and their insect vectors. One such case is the triatomine bugs and the parasite Trypanosoma cruzi, the key actors in Chagas disease. Previous studies have revealed some costs but have not simultaneously examined traits related to development, reproduction, and survival or their possible trade-offs. In addition, these studies have not compared the effects of genetically different T. cruzi strains that differ in their weakening effects in their vertebrate hosts. We compared the body size of the bugs after infection, the number of eggs laid, hatching/non-hatching rate, hatching success, survival, and the resulting number of parasites in Meccus (Triatoma) pallidipennis bugs that were experimentally infected with two strains of T. cruzi (Chilpancingo [CH], the most debilitating in vertebrates; and Morelos [MO], the least debilitating) (both belonging to TcI group). Our results showed that infection affects size (MO < CH; MO and CH = control), number of eggs laid (MO and CH < control) hatching/non-hatching rate (MO < control < CH), hatching success (control < MO, CH = control = MO), and survival (Chilpancingo < Morelos < control). In addition, the CH strain produced more parasites than the MO strain. These results suggest that (a) infection costs depend on the parasite's origin, (b) the more debilitating effects of the CH strain are due to its increased proliferation in the host, and (c) differences in pathogenicity among T. cruzi strains can be maintained through their different effects on hosts' life history traits. Probably, the vectorial capacity mediated by a more aggressive strain could be reduced due to its costs on the triatomine, leading to a lower risk of vertebrate and invertebrate infection in natural populations.

The Fat Body of the Hematophagous Insect, Panstrongylus megistus (Hemiptera: Reduviidae): Histological Features and Participation of the ß-Chain of ATP Synthase in the Lipophorin-Mediated Lipid Transfer.

In insects, lipid transfer to the tissues is mediated by lipophorin, the major circulating lipoprotein, mainly through a nonendocytic pathway involving docking receptors. Currently, the role of such receptors in lipid metabolism remains poorly understood. In this work, we performed a histological characterization of the fat body of the Chagas' disease vector, Panstrongylus megistus (Burmeister), subjected to different nutritional conditions. In addition, we addressed the role of the ß-chain of ATP synthase (ß-ATPase) in the process of lipid transfer from lipophorin to the fat body. Fifth-instar nymphs in either fasting or fed condition were employed in the assays. Histological examination revealed that the fat body was composed by diverse trophocyte phenotypes. In the fasting condition, the cells were smaller and presented a homogeneous cytoplasmic content. The fat body of fed insects increased in size mainly due to the enlargement of lipid stores. In this condition, trophocytes contained abundant lipid droplets, and the rough endoplasmic reticulum was highly developed and mitochondria appeared elongated. Immunofluorescence assays showed that the ß-ATPase, a putative lipophorin receptor, was located on the surface of fat body cells colocalizing partially with lipophorin, which suggests their interaction. No changes in ß-ATPase expression were found in fasting and fed insects. Blocking the lipophorin-ß-ATPase interaction impaired the lipophorin-mediated lipid transfer to the fat body. The results showed that the nutritional status of the insect influenced the morphohistological features of the tissue. Besides, these findings suggest that ß-ATPase functions as a lipophorin docking receptor in the fat body.

MALDI-TOF MS protein profiling for the rapid identification of Chagas disease triatomine vectors and application to the triatomine fauna of French Guiana.

Triatomines are haematophagous insects involved in the transmission of Trypanosoma cruzi, the aetiological agent of Chagas disease. The vector competence of these arthropods can be highly variable, depending on the species. A precise identification is therefore crucial for the epidemiological surveillance of T. cruzi and the determination of at-risk human populations. To circumvent the difficulties of morphological identification and the lack of comprehensiveness of the GenBank database, we hereby propose an alternative method for triatomine identification. The femurs of the median legs of triatomines from eight different species from French Guiana were subjected to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) analysis. Method evaluation was performed on fresh specimens and was applied to dry specimens collected between 1991 and 2003. Femur-derived protein extracts provided reproducible spectra within the same species along with significant interspecies heterogeneity. Validation of the study by blind test analysis provided 100% correct identification of the specimens in terms of the species, sex and developmental stage. MALDI-TOF mass spectrometry appears to be a powerful tool for triatomine identification, which is a major step forward in the fight against Chagas disease.

Behavioural and electrophysiological responses of Triatoma dimidiata nymphs to conspecific faecal volatiles.

The behavioural and electrophysiological (electroantennography) responses of the first two instars of Triatoma dimidiata (Hemiptera: Reduviidae) Latreille to fresh and dry faecal headspace volatile extracts from fifth instar conspecific nymphs and synthetic compounds were analysed in this study. Recently emerged nymphs (3-5 days) aggregated around filter paper impregnated with dry faeces and around filter paper impregnated with extracts from both fresh and dry faeces. Older first instars (10-15 days) and second instars aggregated around filter paper impregnated with fresh and dry faeces, and their respective headspace extracts. Dry faecal volatile extracts elicited the strongest antennal responses, followed by fresh faecal extracts. Gas chromatography-mass spectrometry analysis of dried faecal headspace volatiles demonstrated the presence of 12 compounds: 2-ethyl-1-hexanol, 1,2,4-trimethylbenzene, n-octadecane, n-nonadecane, n-eicosane, n-heneicosane, n-tricosane, n-pentaeicosane, n-hexaeicosane, n-octaeicosane, nonanal, and 4-methyl quinazoline. In fresh faecal headspace extracts, only nonanal was clearly detected, although there were other trace compounds, including several unidentified sesquiterpenes. Four of the 11 compounds tested individually elicited aggregation behaviour at concentrations of 100 ng/µL and 1 µg/µL. A blend containing these four components also mediated the aggregation of nymphs. These volatiles may be valuable for developing monitoring methods and designing sensitive strategies to detect and measure T. dimidiata infestation.

Molecular bloodmeal analyses reveal that Trypanosoma cruzi-infected, native triatomine bugs often feed on humans in houses in central Brazil.

The identification of bloodmeal sources in triatomine bugs (Hemiptera: Reduviidae) is important in understanding vector-host associations and in measuring the risk for Chagas' disease transmission. The bloodmeal sources of triatomines infected with Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae) caught in houses in central Brazil (Goiás State and the Federal District) were investigated during 2012-2014. Mitochondrial cytochrome b amplicons were used to identify bloodmeals through high-resolution melting and DNA sequencing. Most bugs were found to have fed on either humans (45.7%) or chickens (43.1%). Human blood was detected in Triatoma sordida (n = 22/50 bugs), Triatoma pseudomaculata (n = 7/11 bugs), Panstrongylus megistus (n = 10/24 bugs), Panstrongylus geniculatus (n = 1/3 bugs) and Rhodnius neglectus (n = 18/28 bugs) (all: Hemiptera: Reduviidae). Sequencing identified Necromys (Rodentia: Cricetidae) mouse blood in P. geniculatus and Tropidurus (Squamata: Tropiduridae) lizard blood in T. pseudomaculata and T. sordida. These findings reveal new vector-host associations. The present results suggest frequent contact between humans and T. cruzi-infected triatomines in central Brazil and indicate that Chagas' disease transmission by native vectors is an ongoing threat.

Impact of climate change on vector transmission of Trypanosoma cruzi (Chagas, 1909) in North America.

Climate change can influence the geographical range of the ecological niche of pathogens by altering biotic interactions with vectors and reservoirs. The distributions of 20 epidemiologically important triatomine species in North America were modelled, comparing the genetic algorithm for rule-set prediction (GARP) and maximum entropy (MaxEnt), with or without topographical variables. Potential shifts in transmission niche for Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae) (Chagas, 1909) were analysed for 2050 and 2070 in Representative Concentration Pathway (RCP) 4.5 and RCP 8.5. There were no significant quantitative range differences between the GARP and MaxEnt models, but GARP models best represented known distributions for most species [partial-receiver operating characteristic (ROC) > 1]; elevation was an important variable contributing to the ecological niche model (ENM). There was little difference between niche breadth projections for RCP 4.5 and RCP 8.5; the majority of species shifted significantly in both periods. Those species with the greatest current distribution range are expected to have the greatest shifts. Positional changes in the centroid, although reduced for most species, were associated with latitude. A significant increase or decrease in mean niche elevation is expected principally for Neotropical 1 species. The impact of climate change will be specific to each species, its biogeographical region and its latitude. North American triatomines with the greatest current distribution ranges (Nearctic 2 and Nearctic/Neotropical) will have the greatest future distribution shifts. Significant shifts (increases or decreases) in mean elevation over time are projected principally for the Neotropical species with the broadest current distributions. Changes in the vector exposure threat to the human population were significant for both future periods, with a 1.48% increase for urban populations and a 1.76% increase for rural populations in 2050.

[Enfermedad de Chagas en México].

Chagas disease, which is caused by Trypanosoma cruzi, is considered to be the most serious parasitic disease in America. It is transmitted mainly by triatominae ("kissing bugs"). Mazzoti reported the first two human cases in Mexico. The form of transmission is by parasites entering the organism in feces of the insect, by blood transfusion, from mother to child, by organ transplant and laboratory accidents. In Mexico, 1.1 million people are estimated to be infected; the incidence in 2012 was 0.70 per 1,00,000 population. In 2017, the highest incidence rates were registered in Yucatán, Oaxaca and Hidalgo. The infection causes cardiomyopathies and mega-organs of the digestive tract. Diagnosis in the acute phase is by parasitological approach and, in the chronic phase, by laboratory screening studies. In Mexico's blood banks, screening for Chagas disease is mandatory; from 2007 to 2016, seroprevalence has decreased from 0.40 to 0.32 due to the improvement of donor selection processes and the ad hoc questionnaire. The targets of the parasite are neurons and smooth and myocardial muscle cells. The association of neuronal and smooth muscle destruction defines the presentation of chagas mega-syndromes. Initial manifestations of the disease can go unnoticed; 5% show apparent signs and symptoms and 30% will progress to the chronic asymptomatic phase. Currently available treatments have effect in the acute phase. For the control of Chagas disease, the Specific Action Program for the Prevention and Control of Chagas Disease (PAE Chagas 2013-2018) is available to initiate activities aimed at eliminating transfusion and congenital transmission and controlling vector transmission. The success of medical care depends on oportune detection, early etiological treatment and coverage broadening. On the other hand, monitoring and screening of pregnant women living in risk areas and blood and organ donors universal screening will enable the elimination congenital and transfusion transmission.

La enfermedad de Chagas, causada por el Trypanosoma cruzi, está considerada como la parasitosis más grave en América. Se transmite principalmente por triatominos (chinches). El doctor Mazzoti reportó los dos primeros casos humanos en México. La forma de transmisión es por la entrada al organismo de los parásitos en heces del insecto, por transfusión sanguínea, de madre a hijo, por trasplante de órganos y por accidentes de laboratorio. En México se estima que 1.1 millones de personas están infectadas; la incidencia en 2012 fue de 0.70 por 100 000 habitantes. En 2017, las mayores tasas de incidencia se registraron en Yucatán, Oaxaca e Hidalgo. La infección ocasiona miocardiopatías y megaórganos del tracto digestivo. El diagnóstico en fase aguda es por abordaje parasitológico y en fase crónica, por estudios de tamizaje por laboratorio. En los bancos de sangre de México, el estudio de la enfermedad de Chagas es de observancia obligatoria; de 2007 a 2016, la seroprevalencia ha disminuido de 0.40 a 0.32 debido a la mejora de los procesos de selección al donante y al cuestionario ad hoc. Los blancos del parásito son las células neuronales y las de los músculos liso y miocárdico. La asociación de la destrucción neuronal y del músculo liso define la presentación de los síndromes megachagásicos. Las manifestaciones iniciales de la enfermedad pueden pasar desapercibidas; 5 % de los pacientes presenta signos y síntomas aparentes y 30 % evolucionará a la fase crónica asintomática. Los tratamientos actuales tienen efecto en la fase aguda. Para el control de la enfermedad de Chagas se dispone del Programa de Acción Específico para la Vigilancia Prevención y Control de la Enfermedad de Chagas (PAE Chagas 2013-2018), encaminado a eliminar la transmisión transfusional y congénita y a controlar la transmisión vectorial. De la detección oportuna, el tratamiento etiológico temprano y la ampliación de cobertura depende el éxito de la atención médica. Por su parte, la vigilancia y tamizaje de las mujeres embarazadas que viven en zonas de riesgo y el tamizaje universal de donadores de sangre y órganos harán posible la eliminación de la transmisión connatal y transfusional.

Geographic Distribution and Ecology of Triatoma dimidiata (Hemiptera: Reduviidae) in Colombia.

Triatoma dimidiata Latreille is the second most important vector of Chagas' disease in Colombia and is found in urban and periurban areas. From January 2007 to June 2008, we performed field work in 8 departments, 18 municipalities, and 44 rural villages, covering most of its known distribution and all of its ecological zones in the country. The goal was to determine the geographical distribution, the ecology, and house infestation indices of T. dimidiata over its range and hence the Chagas' disease transmission risk. In Colombia, T. dimidiata occupies a wide variety of ecosystems, from transformed ecosystems in the Andean biome with shrub and xerofitic vegetation to very dense forests in the humid tropical forests in the Sierra Nevada of Santa Marta. According to genetic and ecological criteria, at least two T. dimidiata forms of this species are present: populations from the northwest of the country (Caribbean plains) are restricted to palm tree habitats, and domestic involvement is limited to sporadic visits because of attraction by light; and populations of the east region (Andean mountains) presenting a complex distributional pattern including sylvatic, peridomestic, and domiciliated ecotopes, and occupying a great variety of life zones. The latter population is of epidemiological importance due to the demonstrated migration and genetical flow of individuals among the different habitats. Control, therefore, must take into account its diversity of habitats.

Mosquito Vector Biology and Control In Latin America-A 26th Symposium.

The 26th Annual Latin American Symposium presented by the American Mosquito Control Association (AMCA) was held as part of the 82nd Annual Meeting of the AMCA in Savannah, GA, in February 2016. The principal objective, as for the previous 25 symposia, was to promote participation in the AMCA by vector control specialists, public health workers, and academicians from Latin America. This publication includes summaries of 19 presentations that were given orally in Spanish by participants from Colombia, Ecuador, Mexico, and the USA. Topics addressed in the symposium included: surveillance, operations, ecology, chemical control, natural products, biological control, and insecticide resistance. Additionally, vector studies included malaria, dengue virus, and chikungunya virus transmission studies. The first reports and characterizations of infections in Mexico were reported during the symposium. Insect vectors included Aedes, Culex, and Anopheles mosquitoes in addition to ticks and triatomines.

Global Climate Change Effects on Venezuela's Vulnerability to Chagas Disease is Linked to the Geographic Distribution of Five Triatomine Species.

We analyzed the possible effects of global climate change on the potential geographic distribution in Venezuela of five species of triatomines (Eratyrus mucronatus (Stal, 1859), Panstrongylus geniculatus (Latreille, 1811), Rhodnius prolixus (Stål, 1859), Rhodnius robustus (Larrousse, 1927), and Triatoma maculata (Erichson, 1848)), vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. To obtain the future potential geographic distributions, expressed as climatic niche suitability, we modeled the presences of these species using two IPCC (Intergovernmental Panel on Climate Change) future emission scenarios of global climate change (A1B and B1), the Global Climate model CSIRO Mark 3.0, and three periods of future projections (years 2020, 2060, and 2080). After estimating with the MaxEnt software the future climatic niche suitability for each species, scenario, and period of future projections, we estimated a series of indexes of Venezuela's vulnerability at the county, state, and country level, measured as the number of people exposed due to the changes in the geographical distribution of the five triatomine species analyzed. Despite that this is not a measure of the risk of Chagas disease transmission, we conclude that possible future effects of global climate change on the Venezuelan population vulnerability show a slightly decreasing trend, even taking into account future population growth; we can expect fewer locations in Venezuela where an average Venezuelan citizen would be exposed to triatomines in the next 50-70 yr.

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.

Circulation of Trypanosoma cruzi in triatomines and Didelphis sp. in urban areas: Transmission risk assessment in the Metropolitan Region.

The presence of Trypanosoma cruzi vectors in urban areas has been frequent, with colonization of homes and associated with reservoir animals that increase risk to humans, with simultaneous circulation of vectors and T. cruzi. The study aimed to describe the circulation of triatomines and T. cruzi in the Metropolitan Region of São Paulo, as well as evaluate risk situations. For analysis purposes, the triatomine notification information from January 2016 to July 2023 was used. While for Didelphis sp. collection with the aid of traps, notification information used was from 2019 to 2023. Information about triatomines came from spontaneous demand by the population and notification services were carried out by state field teams following defined protocols. 202 notifications were received with the capture of 448 triatomines. The positivity for T. cruzi observed was 60.5%. Regarding Didelphis sp., 416 animals were collected, 5.3% of which were positive for T. cruzi. There was overlapping areas of presence of infected triatomines and Didelphis sp., whose Discrete Typing Unit (DTU) was T. cruzi I. This work indicates the presence of infected vectors in urban areas, and the presence of a wild cycle of T. cruzi in didelphiids, reaffirming the need for and importance of vector surveillance work, through actions that can prevent the transmission of Chagas disease.