Triatomine Species Research Articles

Using iNaturalist presence data to produce suitability maps for Triatoma protracta, T. rubida and T. recurva in the American Southwest, Texas and northern Mexico, to identify potential transmission zones of Chagas disease.

There are 11 species of triatomines in the USA, with seven reported in the American Southwest. These species are capable of transmitting Trypanosoma cruzi, the etiological agent of Chagas disease, but are generally sylvatic and rarely infect humans in the USA. iNaturalist is one of the most popular citizen science data portals, where users record encounters with any individual organism. As of November 2023, iNaturalist reported 722 confirmed triatomine observations in the American Southwest. Maximum entropy ecological niche modelling and bioclimatic environmental variables were used to predict zones of highest human-triatomine interaction. Models fit well for Triatoma protracta (0.85), T. rubida (0.94), and T. recurva (0.96). Precipitation in the warmest quarter was most predictive of T. protracta presence, while precipitation in the driest quarter was most predictive of T. rubida and T. recurva. Locations identified in the American Southwest with highest potential for human-triatomine interaction, and potential T. cruzi transmission, were coastal California, the Sierra Nevada foothills, southern Arizona and border areas of northern Mexico. Study findings can be used for targeted surveillance efforts to address the paucity of contemporary information regarding triatomine species diversity and geographical and ecological associations in the American Southwest.

Sugar feeding in triatomines: a new perspective for controlling the transmission of Chagas disease.

Introduction: Triatomines are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Currently, there is no vaccine against this disease. Thus, control of the insect vector population is the main strategy available to reduce the number of cases. Triatomines are considered obligate hematophagous, but different alternative feeding behaviors were described, such as haemolymphagy or plant feeding. Methods: To determine the preference for sugar feeding in nymphs and adults of Rhodnius prolixus, the insects were exposed a piece of cotton containing bromophenol blue plus sucrose. In addition, we offered several sugars for different species of triatomines, and tested sugar meals as a route of delivery of insecticides in first-instar nymphs of R. prolixus. The effect of sugar feeding on the physiology of these different species of triatomines was recorded. Results: First instar nymphs ingested sucrose more strongly than other stages, and showed high mortality rates. In different species of triatomines, sucrose induced an ingestion, but engorgement varied according to the species. R. prolixus nymphs showed an indiscriminate intake of various sugars, with very different physiological effects. Furthermore, ingesting different combinations of insecticides + sugar significantly reduced insect survival. Discussion: In summary, we described for the first-time sugar feeding as a widespread behavior in several species of triatomines, and the possibility of the use of toxic sugar baits for the control of these vectors. The knowledge of feeding behavior in these insects can be fundamental for the development of new strategies to control Chagas disease.

Genome report: First whole genome sequence of Triatoma sanguisuga (Le Conte, 1855), vector of Chagas disease.

Triatoma sanguisuga is the most widespread triatomine bug species in the United States (US). The species vectors the human parasite Trypanosoma cruzi , which causes Chagas disease. Vector-borne Chagas disease is rarely diagnosed in the US, but T. sanguisuga has been implicated in a handful of cases. Despite its public health importance, little is known about the genomics or population genetics of T. sanguisuga . Here, we used long-read sequencing to assemble the first whole genome sequence for T. sanguisuga using DNA extracted from one adult specimen from Delaware. The final size of the genome was 1.162 Gbp with 77.7x coverage. The assembly consisted of 183 contigs with an N50 size of 94.97 Kb. The Benchmarking Universal Single-Copy Ortholog (BUSCO) complete score was 99.1%, suggesting a very complete assembly. Genome-wide GC level was 33.56%, and DNA methylation was 18.84%. The genome consists of 61.4% repetitive DNA and 17,799 predicted coding genes. The assembled T. sanguisuga genome was slightly larger than that of Triatominae species Triatoma infestans and Rhodnius prolixus (949 Mbp with 90.4% BUSCO score and 706 Mbp with 96.5% BUSCO score, respectively). The T. sanguisuga genome is the first North American triatomine species genome to be sequenced, and it is the most complete genome yet for any Triatominae species. The T. sangsuiga genome will allow for deeper investigations into epidemiologically relevant aspects of this important vector species, including blood feeding, host seeking, and parasite competence, thus providing potential vector-borne disease management targets and strengthening public health preparedness.

Chagas Disease Vectors of Alagoas, Brazil: First Report of Panstrongylus geniculatus (Latreille, 1811) (Hemiptera, Triatominae) in the Brazilian State and Update of the Dichotomous Key Based on Cytogenetic Data.

Panstrongylus geniculatus is the most widely distributed species of Panstrongylus in Brazil and merits attention from vector control programs due to its potential for domiciliation. Specimens infected with Trypanosoma cruzi have already been reported in both peridomiciliary and domiciliary environments. Building on these findings, we report, for the first time, the presence of P. geniculatus in the state of Alagoas and provide an updated dichotomous key (based on cytogenetic data) for species in Alagoas. Panstrongylus geniculatus has been identified in Boca da Mata, Joaquim Gomes, and Novo Lino. In light of the recent notification of Rhodnius domesticus and this record of P. geniculatus, we present an updated identification key enabling the differentiation of all species in Alagoas. Emphasis is placed on the importance of correctly identifying triatomine species because it is crucial for the development of effective control measures, thereby aiding in the mitigation of Chagas disease.

A baited trap for kissing bugs (Hemiptera: Reduviidae: Triatominae)

Chagas disease is a key vector-borne disease. This illness is caused by Trypanosoma cruzi Chagas, which is transmitted by triatomine bugs. Largely, the control of this disease relies on reducing such contact. We optimized the performance of a box trap in laboratory conditions to capture four triatomine species: Triatoma pallidipennis (Stål), Triatoma infestans Klug, Triatoma phyllosoma (Burmeister), and Rhodnius prolixus Stål. We varied four components for a box trap: material, color, height, and bait attractants. All species were captured more in corrugated cardboard traps than in other trap material. Moreover, T. infestans and R. prolixus were also captured in plywood traps. T. pallidipennis preferred traps of 15 × 15 × 4 cm and 20 × 20 × 4 cm, while T. phyllosoma and T. infestans were more captured in traps of 10 × 10 × 4 cm, and 15 × 15 × 4 cm. Rhodnius prolixus was more captured to 10 × 10 × 4 cm traps. T. pallidipennis was trapped with traps of any color tested, T. phyllosoma and T. infestans were captured more in red and yellow traps, and R. prolixus was mostly captured in blue, violet, and yellow traps. Triatoma pallidipennis was captured at any height above the ground, while T. phyllosoma, T. infestans, and R. prolixus were mostly captured 50, 100, and 150 cm above the ground. Regarding the lure, T. pallidipennis was trapped with four aldehydes + lactic acid + ammonia; T. infestans and R. prolixus were trapped with a blend of four aldehydes + lactic acid, a blend of the four aldehydes + ammonia, and a blend of four aldehydes + lactic acid + ammonia. Triatoma phyllosoma was trapped with any lure tested. These results showed that the trap boxes offer an alternative method for controlling Chagas disease.

What happens when the insecticide does not kill? A review of sublethal toxicology and insecticide resistance in triatomines.

Chagas disease is considered one of the most important human parasitosis in the United States. This disease is mainly transmitted by insects of the subfamily Triatominae. The chemical vector control is the main tool for reducing the incidence of the disease. However, the presence of triatomines after pyrethroids spraying has been reported in some regions, as in the case of Triatoma infestans in Argentina and Bolivia. The presence of insects can be explained by the colonization from neighbouring areas, the reduction of insecticide dose to sublethal levels due to environmental factors, and/or by the evolution of insecticide resistance. In the last two scenarios, a proportion of the insects is not killed by insecticide and gives rise to residual populations. This article focuses on the toxicological processes associated with these scenarios in triatomines. Sublethal doses may have different effects on insect biology, that is, sublethal effects, which may contribute to the control. In addition, for insect disease vectors, sublethal doses could have negative effects on disease transmission. The study of sublethal effects in triatomines has focused primarily on the sequence of symptoms associated with nervous intoxication. However, the effects of sublethal doses on excretion, reproduction and morphology have also been studied. Rhodnius prolixus and T. infestans and pyrethroids insecticides were the triatomine species and insecticides, respectively, mainly studied. Insecticide resistance is an evolutionary phenomenon in which the insecticide acts as a selective force, concentrating on the insect population's pre-existing traits that confer resistance. This leads to a reduction in the susceptibility to the insecticide, which was previously effective in controlling this species. The evolution of resistance in triatomines received little attention before the 2000s, but after the detection of the first focus of resistance associated with chemical control failures in T. infestans from Argentina in 2002, the study of resistance increased remarkably. A significant number of works have studied the geographical distribution, the resistance mechanisms, the biological modifications associated with resistance, the environmental influences and the genetic of T. infestans resistant to pyrethroid insecticides. Currently, studies of insecticide resistance are gradually being extended to other areas and other species. The aim of this article was to review the knowledge on both phenomena (sublethal effects and insecticide resistance) in triatomines. For a better understanding of this article, some concepts and processes related to insect-insecticide interactions, individual and population toxicology and evolutionary biology are briefly reviewed. Finally, possible future lines of research in triatomine toxicology are discussed.

Range size positively correlates with temperature and precipitation niche breadths but not with dietary niche breadth in triatomine insects, vectors of Chagas disease.

Ecological theory predicts that species that can utilise a greater diversity of resources and, therefore, have wider niche breadths should also occupy larger geographic areas (the 'niche breadth-range size hypothesis'). Here, we tested this hypothesis for a blood-sucking group of insects of medical significance: the Triatominae (aka 'kissing bugs') (Hemiptera: Reduviidae). Given that niches can be viewed from different perspectives, we tested this hypothesis based on both dietary and climatic niches. We assembled the most complete dataset of triatomine feeding patterns to date by reviewing 143 studies from the literature up to 2021 and tested whether the niche breadth-range size hypothesis held for this group for both dietary and climatic components of the niche. Temperature and precipitation niche breadths were estimated from macro-environmental variables, while diet breadth was calculated based on literature data that used PCR and/or ELISA to identify different types of hosts as blood sources per triatomine species. Our results showed that temperature and precipitation niche breadths, but not dietary breadth, were positively correlated with range sizes, independent of evolutionary history among species. These findings support the predictions from the range size-niche breadth hypothesis concerning climate but not diet, in Triatominae. It also shows that support for the niche breadth-range size hypothesis is dependent upon the niche axis under consideration, which can explain the mixed support for this hypothesis in the ecological literature.

Behavioral and biological parameters of six populations of Triatoma pallidipennis (Heteroptera: Reduviidae) from areas with high and low prevalence rates of Trypanosoma cruzi human infection

In Mexico, more than 30 species of triatomines, vectors of Trypanosoma cruzi, the etiological agent of Chagas disease, have been collected. Among them, Triatoma pallidipennis stands out for its wide geographical distribution, high infection rates and domiciliation. Local populations of triatomines have shown notable biological and behavioral differences, influencing their vectorial capacity. Six behaviors of epidemiological importance, namely, egg-to-adult development time, median number of blood meals to molt to the next instar, instar mortality rates, aggressiveness (delay in initiating a meal), feeding time and defecation delay, were evaluated in this study for six populations of T. pallidipennis. Those populations from central, western and southern Mexico were arranged by pairs with a combination of high (HP) and medium (MP) of Trypanosoma cruzi human infection and most (MFC) and low (CLF) collection frequencies: HP/MFC, HP/CLF, and MP/MFC. The development time was longer in HP/CLF populations (> 220 days). The median number of blood meals to molt was similar (7–9) among five of the six populations. Mortality rates were greater (> 40 %) in HP/CLF and one MP/MFC populations. All studied populations were aggressive but exhibited slight differences among them. The feeding times were similar (≥ 10 min) for all studied populations within instars, increasing as instars progressed. An irregular pattern was observed in defecation behaviors, with marked differences even between the two populations from the same pair. High percentages of young (57.3–87.9 %), and old (62.4–89.8 %) nymphs, of female (61.1–97.3 %) and male (65.7–93.1 %) of all the studied populations defecated quickly (while eating, immediately after finishing feeding or < 1 min postfeeding). Our results indicate that the HP/MFC populations are potentially highly effective vectors for transmitting T. cruzi infections, while HP/CLF populations are potentially less effective vectors T. cruzi infections.

Variety is the spice: The role of morphological variation of Triatoma infestans (Hemiptera, Reduviidae) at a macro-scale

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi (Chagas, 1909). One of the primary vectors of T. cruzi in South America is Triatoma infestans (Klug, 1834). This triatomine species is distributed across a huge latitudinal gradient, inhabiting domiciliary , peridomiciliary , and wild environments. Its wide geographic distribution provides an excellent opportunity to study the relationships between environmental gradients and intraspecific morphological variation. In this study, we investigated variations in wing size and shape in T. infestans across six ecoregions. We aimed to address the following questions: How do wing size and shape vary on a regional scale, does morphological variation follow specific patterns along an environmental or latitudinal gradient, and what environmental factors might contribute to wing variation? Geometric morphometric methods were applied to the wings of 162 females belonging to 21 T. infestans populations, 13 from Argentina (n = 105), 5 from Bolivia (n = 42), and 3 from Paraguay (n = 15). A comparison of wing centroid size across the 21 populations showed significant differences. Canonical Variate Analysis (CVA) revealed significant differences in wing shape between the populations from Argentina, Bolivia, and Paraguay, although there was a considerable overlap, especially among the Argentinian populations. Well-structured populations were observed for the Bolivian and Paraguayan groups. Two analyses were performed to assess the association between wing size and shape, geographic and climatic variables: multiple linear regression analysis (MRA) for size and Partial Least Squares (PLS) regression for shape. The MRA showed a significant general model fit. Six temperature-related variables, one precipitation-related variable, and the latitude showed significant associations with wing size. The PLS analysis revealed a significant correlation between wing shape with latitude, longitude, temperature-related, and rainfall-related variables. Wing size and shape in T. infestans populations varied across geographic distribution. Our findings demonstrate that geographic and climatic variables significantly influence T. infestans wing morphology.

Novel finding of Panstrongylus rufotuberculatus (Champion, 1899) (Hemiptera, Reduviidae, Triatominae) in Belize, with a note on single Rhodnius St&amp;aring;l, 1859 species observations

We report Triatominae species Panstrongylus rufotuberculatus (Champion, 1899) for the first time in Belize. The specimen was collected in Cayo District, Belize in 2003 and later discovered in 2023 in a research collection. The distribution of P. rufotuberculatus spans Mexico to Argentina, and Belize lies within this range. This finding represents the fifth triatomine species reported in Belize, but only two species, Triatoma dimidata Latreille, 1811 and T. mopan Dorn et al., 2018, have been reported more than once. More research is needed to fully understand Triatominae biodiversity in Belize.

Chemical symphony: Unraveling triatomine aggregation and attraction patterns for innovative pest control solutions

Aggregation is a spatial distribution pattern where individuals can be grouped through interaction with particular signals or cues [e.g., chemical substances]. Numerous triatomine species exhibit attraction and aggregation around both conspecific and heterospecific feces. It remains unclear whether compounds released by feces function as signals (pheromones or synomones) or cues. Employing a bioassay that mimics field conditions, we investigated the response of Triatoma pallidipennis bugs to volatiles present in its feces and blends of these compounds. Our findings indicate that short-chain aldehydes, namely nonanal, octanal, heptanal, and hexanal, attract fifth-instar nymphs. Furthermore, insects responded to individual compounds as well as secondary, ternary, and quaternary blends. The most attractive blend consisted of all four aldehydes. Additionally, quaternary blends at various compound ratios attracted fifth-instar nymphs of T. phyllosoma and T. longipennis. We discuss the potential roles of these compounds as signals or cues and explore their application as bait in control programs.

Association between environmental gradient of anthropization and phenotypic plasticity in two species of triatomines

BackgroundTriatoma garciabesi and T. guasayana are considered secondary vectors of Trypanosoma cruzi and frequently invade rural houses in central Argentina. Wing and head structures determine the ability of triatomines to disperse. Environmental changes exert selective pressures on populations of both species, promoting changes in these structures that could have consequences for flight dispersal. The aim of this study was to investigate the relationship between a gradient of anthropization and phenotypic plasticity in flight-related traits.MethodsThe research was carried out in Cruz del Eje and Ischilín departments (Córdoba, Argentina) and included 423 individuals of the two species of triatomines. To measure the degree of anthropization, a thematic map was constructed using supervised classification, from which seven landscapes were selected, and nine landscape metrics were extracted and used in a hierarchical analysis. To determine the flight capacity and the invasion of dwellings at different levels of anthropization for both species, entomological indices were calculated. Digital images of the body, head and wings were used to measure linear and geometric morphometric variables related to flight dispersion. One-way ANOVA and canonical variate analysis (CVA) were used to analyze differences in size and shape between levels of anthropization. Procrustes variance of shape was calculated to analyze differences in phenotypic variation in heads and wings.ResultsHierarchical analysis was used to classify the landscapes into three levels of anthropization: high, intermediate and low. The dispersal index for both species yielded similar results across the anthropization gradient. However, in less anthropized landscapes, the density index was higher for T. garciabesi. Additionally, in highly anthropized landscapes, females and males of both species exhibited reduced numbers. Regarding phenotypic changes, the size of body, head and wings of T. garciabesi captured in the most anthropized landscapes was greater than for those captured in less anthropized landscapes. No differences in body size were observed in T. guasayana collected in the different landscapes. However, males from highly anthropized landscapes had smaller heads and wings than those captured in less anthropized landscapes. Both wing and head shapes varied between less and more anthropogenic environments in both species.ConclusionsResults of the study indicate that the flight-dispersal characteristics of T. garciabesi and T. guasayana changed in response to varying degrees of anthropization.Graphical

Detection and Genotyping of Trypanosoma cruzi Samples in Species of Genus Rhodnius from Different Environments in the Brazilian Amazon.

Background: In the Amazon region, several species of triatomines occur in the natural environments. Among them, species of the genus Rhodnius are a risk to human populations due to their high rates of infection with Trypanosoma cruzi. The aim of this study was to identify the T. cruzi genotypes in Rhodnius specimens and their relationship with sylvatic hosts from different environments in the Brazilian Amazon. Methods: A total of 492 triatomines were collected from the municipalities of Monte Negro, Rondônia state, and Humaitá, Amazonas state, 382 of them being nymphs and 110 adults. Genotyping of T. cruzi in six discrete typing units (DTUs) was performed using conventional multilocus PCR. The triatomines that were positive for T. cruzi and engorged with blood were also targeted for amplification of the cytochrome B (cytB) gene to identify bloodmeal sources. Results: Of the 162 positive samples, the identified DTUs were TcI (87.65%) and TcIV (12.35%). It was observed that 102 specimens were engorged with a variety of bloodmeals. Triatomines infected with TcI were associated with DNA of all identified vertebrates, except Plecturocebus brunneus. TcIV was detected in triatomines that fed on Coendou prehensilis, Didelphis marsupialis, Mabuya nigropunctata, P. brunneus, Pithecia irrorata, Sapajus apella, and Tamandua tetradactyla. Conclusion: Results highlight the need to understand the patterns of T. cruzi genotypes in Rhodnius spp. and their association with sylvatic hosts to better elucidate their role in the transmission of Chagas disease in the Amazon region.

The Unfortunate Abundance of Trypanosoma cruzi in Naturally Infected Dogs and Monkeys Provides Unique Opportunities to Advance Solutions for Chagas Disease

Trypanosoma cruzi, the protozoan parasite and cause of Chagas disease, is widely distributed in many vertebrate and triatomine species throughout North, Central, and South America. Variations in housing quality largely determines human infection risk in the Americas. However, the southern U.S. contains widespread, infected triatomine vectors and captive species and domesticated animals with active T. cruzi infection or at high risk of becoming infected and developing Chagas disease. There is a critical need for better detection and intervention strategies, principally focused on human infection throughout the Americas, but mainly in the U.S., for high-value dogs employed in government and other work. In addition to this economic impact, the concentration of largely unavoidable T. cruzi infections in U.S. dogs provides an incomparable opportunity to answer questions related to T. cruzi infection and Chagas disease that are impossible or unethical to address in humans. As the course of T. cruzi infection and Chagas disease, the immune response to infection, and the response to therapeutics are highly similar across the range of mammalian host species, information obtained from studies in other species can directly inform researchers on how to best detect, manage, and treat T. cruzi infection and Chagas disease in humans.

GeoVin - a project with technological innovation and community participation for the comprehensive approach to Chagas disease and triatomines (Hemiptera: Reduviidae)

Chagas disease is one of the most important public health problems in America, involving triatomines (Hemiptera: Reduviidae: Triatominae) in the vectorial transmission of Trypanosoma cruzi (Protista: Kinetoplastea: Trypanosomatidae). In Argentina, 15 species of triatomines are distributed, of which seven are the most common in the domicile and peridomicile, while the rest are mainly associated with wild environments. Due to the lack of updated data of geographic distribution, the GeoVin Project arises to provide not only a triatomine digital tool of triatomine notification, but also resources with information about Chagas and triatomine vectors. The aim of this paper is to present, describe and highlight the progress of the project, emphasizing the principles of participatory science and entomological surveillance. So far, more than 2,300 web visits have been recorded and the application has been downloaded over 3,400 times. The contribution of the project in articulating with the corresponding government health agencies and the immediacy of the interaction with the community are key elements for the project success. At the same time, the information collected is a constant input for updating the geographical distributions of Argentinian triatomines.

The distribution of triatomine (Hemiptera: Reduviidae) vectors of Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) in Illinois and Missouri: historical records and specimen submissions from community science programs.

Triatomine species (kissing bugs) infected with Trypanosoma cruzi are found across the southern United States. The northern limits of Trypanosoma cruzi infected kissing bugs are less understood. The objective of this work was to describe the locations of kissing bugs from Illinois and Missouri based on historical records, submissions to Texas A&M University's (TAMU) Kissing Bug Community Science Program and the Centers for Disease Control and Prevention (CDC), and records from online platforms (iNaturalist, BugGuide, and GBIF) up to and including 2022. A total of 228 records were discovered, including 186 from historical or observation platforms and 42 specimens submitted to TAMU or CDC. Species included Triatoma sanguisuga (221 total records, 9 nymphs) and Triatoma lecticularia (7 records). Notably, nearly all (24/26) records submitted to TAMU were collected indoors. Twelve of the 30 (40%) specimens tested were positive for the presence of T. cruzi, including parasite discrete taxonomic units TcI and TcIV. One triatomine sample had been found in a bed feeding on the submitter; this bug was positive for T. cruzi and had evidence of human blood in its gut. Records suggest a ubiquitous distribution in Missouri and potentially to the northernmost border in Illinois. Further investigations into triatomine distribution and infection status are needed within states assumed to be northern limits in order to create public health and veterinary health messaging and baseline distributional maps from which to measure future range shifts in relation to a changing climate.

Parasitological and molecular characterization of Trypanosoma cruzi of triatomines and mammals from endemic areas for Chagas disease in Venezuela.

It is estimated that 6-7 million people worldwide are infected with Trypanosoma cruzi, the parasite that causes Chagas disease. In Venezuela, Chagas disease remains a public health problem. In this work, T. cruzi isolates from six species of triatomines and mammals of the orders Didelphimorphia and Xenarthra, captured in rural communities of Monagas, underwent parasitological and molecular characterization. A total of 471 triatomines and 17 mammals were captured, with a natural infection rate of 41.4% and 70.6%, respectively. In the male NMRI mouse model used for parasitological characterization (prepatent period, parasitemia curve, mouse mortality, and tissular parasitism), T. cruzi isolates exhibited high lethality due to their pronounced virulence, irrespective of the parasite load in each mouse, resulting in a mortality rate of 75%. Among the vector isolates, in the mouse model, only 2 out of 6 remained alive, while the rest perished during the evaluation. Conversely, the isolates from mammals proved fatal for all the inoculated mice. All isolates were identified as belonging to DTU TcI, based on the molecular markers such as the intergenic region of the miniexon, D7 divergent domain of the 24Sα rDNA, size-variable domain of the 18S rDNA, and hsp60-PCR-RFLP-EcoRV. This study demonstrates the presence of vectors and mammalian reservoirs naturally infected with T. cruzi in communities of Monagas, the 9th largest and 9th most populous state in Venezuela. This situation represents a neglected epidemiological problem demanding urgent attention and imperative health care intervention.

Infection with Trypanosoma Cruzi Chagas and Characterization of Human Habitats of Triatoma Picturata (Usinger) in Western Mexico.

Chagas disease is one of the most important vector-borne diseases in Latin America. Triatoma picturata (Usinger), distributed in western Mexico, is one of the most important vectors of Trypanosoma cruzi Chagas. Knowing the type and materials used for building homes could lead to improved methods for controlling triatomines by focusing efforts on controlling every species of triatomine in its specific microhabitat. Houses in three studied localities of western Mexico that harbored T. picturata were characterized, as well as two entomological indices. Infestation Index values varied from 10.8% to 51.9% in the three localities, whereas Natural Infection Index values varied from 18.1% to 35.2%. Characteristics of houses invaded by T. picturata also varied. In Juan Gil Preciado, with the highest Entomological Index values, most houses were built of adobe walls with a roof of clay tiles and a dirt floor, and included the presence of domestic animals. Our data indicate that the potential risk of infection with T. cruzi differs markedly for inhabitants of the three studied localities, which demonstrates the importance of studying local populations of triatomines. Our study should contribute to decision-making regarding triatomine control efforts by providing profiles of houses that are more susceptible to triatomine invasion.

Assessing the impact of host predation with Holling II response on the transmission of Chagas disease

Chagas disease is a zoonosis caused by the protozoan parasite Trypanosoma cruzi and transmitted by a broad range of blood-sucking triatomine species. Recently, it is recognized that the parasite can also be transmitted by host ingestion. In this paper, we propose a Chagas disease model incorporating two transmission routes of biting-defecation and host predation between vectors and hosts with Holling II functional response. The basic reproduction number R_v of triatomine population and basic reproduction numbers R_0 of disease population are derived analytically, and it is shown that they are insufficient to serve as threshold quantities to determine dynamics of the model. Our results have revealed the phenomenon of bistability, with backward and forward bifurcations. Specifically, if R_v&gt;1, the dynamic is rather simple, namely, the disease-free equilibrium is globally asymptotically stable as R_0&lt;1 and a unique endemic equilibrium is globally asymptotically stable as R_0&gt;1. However, if R_v&lt;1, there exists a backward bifurcation with one unstable and one stable positive vector equilibria, and bistability phenomenon occurs, revealing that different initial conditions may lead to disease extinction or persistence even if the corresponding R_0&gt;1. In conclusion, predation transmission in general reduces the risk of Chagas disease, whilst it makes the complexity of Chagas disease transmission, requiring an integrated strategy for the prevention and control of Chagas disease.

Vector species richness predicts local mortality rates from Chagas disease

Vector species richness may drive the prevalence of vector-borne diseases by influencing pathogen transmission rates. The dilution effect hypothesis predicts that higher biodiversity reduces disease prevalence, but with inconclusive evidence. In contrast, the amplification effect hypothesis suggests that higher vector diversity may result in greater disease transmission by increasing and diversifying the transmission pathways. The relationship between vector diversity and pathogen transmission remains unclear and requires further study. Chagas disease is a vector-borne disease most prevalent in Brazil and transmitted by multiple species of insect vectors of the subfamily Triatominae, yet the drivers of spatial variation in its impact on human populations remain unresolved. We tested whether triatomine species richness, latitude, bioclimatic variables, human host population density, and socioeconomic variables predict Chagas disease mortality rates across over 5000 spatial grid cells covering all of Brazil. Results show that species richness of triatomine vectors is a good predictor of mortality rates caused by Chagas disease, which supports the amplification effect hypothesis. Vector richness and the impact of Chagas disease may also be driven by latitudinal components of climate and human socioeconomic factors. We provide evidence that vector diversity is a strong predictor of disease prevalence and give support to the amplification effect hypothesis.