Triatoma brasiliensis Neiva, 1911: food sources and diversity of Trypanosoma cruzi in wild and artificial environments of the semiarid region of Ceará, northeastern Brazil

Entomological indicators and food sources of triatomines in the Brazilian semi-arid region

BACKGROUND

Triatomines are biological vectors of Trypanosoma cruzi, the etiological agent of Chagas Disease (CD) and have various mammalian hosts. This study evaluated the entomological indicators and food sources of triatomines in Petrolina in the semi-arid region of Brazil, where CD is endemic.

METHODS

Triatomines were captured indoors and outdoors through an active search and entomological indices (household and natural infections) were calculated. Parasitological analyses were performed through microscopic visualization using Giemsa-stained insect feces, and DNA sequencing was employed to identify food sources from the gut contents of 82 insects (9.05%) that were better preserved.

RESULTS

We captured triatomines (906) in peridomicile (807) and intradomicile (99): Triatoma brasiliensis (84.7%, 767 specimens), Triatoma spp. (8.2%, 74 specimens), T. pseudomaculata (6.5%, 59 specimens), Rhodnius spp. (0.4%, four specimens), R. nasutus (0.1%, one specimen), and T. sordida (0.1%, one specimen). The household infestation index is 11.8%. Thirty-five triatomines were infected (33 T. brasiliensis and two T. pseudomaculata), corresponding to a natural infection index of 3.8%. The identified food sources were human T. pseudomaculata and T. brasiliensis, dogs for T. brasiliensis and rodents (Mus musculus) for T. brasiliensis.

CONCLUSIONS

The results reinforce the need to intensify CD diagnosis, surveillance, and control actions, as an increase in entomological indices was recorded. Blood from humans and domestic and synanthropic animals was detected in the infected triatomines, suggesting a risk of CD vector transmission in Petrolina. As CD is a zoonosis, multidisciplinary and intersectoral CD surveillance must be conducted in the context of the One Health.

Spatial distribution of Triatoma dimidiata peridomestic colonies modulated by distance between susceptible microhabitat patches

Triatoma dimidiata is a vector of the hemoparasite Trypanosoma cruzi, the causal agent of Chagas disease. It settles reproductive colonies in the peridomicile of the premises. The peridomicile is comprised of a random set of artificial and natural features that overlap and assemble a network of microenvironmental suitable sites (patches) that interact with each other and favor the structure and proliferation of T. dimidiata colonies. The heterogeneity of patch characteristics hinders the understanding and identification of sites susceptible to colonization. In this study, a classification system using a random forest algorithm was used to identify peridomiciles susceptible to colonization to describe the spatial distribution of these sites and their relationship with the colonies of T. dimidiata in ten localities of Yucatan. From 1,000 peridomiciles reviewed, the classification showed that 13.9 % (139) of the patches were highly susceptible (HSP), and 86.1 % (861) were less susceptible (LSP). All localities had at least one HSP. The occupancy by patch type showed that the percentage of total occupancy and by colonies was higher in the HSP, while the occupancy by adult T. dimidiata without evidence of nymphs or exuviae (propagules) was higher in the LSP. A generalized additive model (GAM) revealed that the percentage of occupied patches increases as the abundance of individuals in the localities increases however, the percentage of occupied patches in LSP is lower than occupied in HSP. Distance analyses revealed that colonies and propagules were located significantly closer (approximately 200 m) to a colony in a HSP than any colony in a LSP. The distribution of T. dimidiata in the localities was defined by the distribution of patch type; as the occupancy in these patches increased, a network of peridomestic populations was configured, which may be promoted by a greater abundance of insects inside the localities. These results reveal that the spatial distribution of T. dimidiata individuals and colonies in the peridomicile at the locality scale corresponds to a metapopulation pattern within the localities through a system of patches mediated by distance and level of the vectors' occupancy.

Population genetics and genomics of Triatoma brasiliensis (Hemiptera, Reduviidae) in an area of high pressure of domiciliary infestation in Northeastern Brazil

Understanding the population dynamics of vectors is crucial for effective control of vector-borne diseases. In the Northeastern Brazilian semi-arid region, Triatoma brasiliensis persists as the most significant Chagas disease vector, frequently displaying recurrent domiciliary infestations. This situation raises relevant public health concerns in the municipality of Currais Novos in the state of Rio Grande do Norte. This area has experienced a high prevalence of peridomiciliary re-infestations by T. brasiliensis, coupled with elevated rates of Trypanosoma cruzi infection. Therefore, we assessed the distribution of genetic variation via mitochondrial Cytochrome b gene (MT-CYB) sequencing (n = 109) and single nucleotide polymorphisms (SNPs, n = 86) to assess the gene flow among distinct populations distributed in varied geographic spots and environments, mainly sylvatic and peridomiciliary. Insects were collected from rural communities at Currais Novos, enclosed within a 16 km radius. Sampling included 13 populations: one intradomiciliary, eight peridomiciliary, and four sylvatic. Furthermore, an external population located 220 km from Currais Novos was also included in the study. The method employed to obtain SNP information relied on ddRAD-seq genotyping-by-sequencing (GBS), enabling a genome-wide analysis to infer genetic variation. Through AMOVA analysis of MT-CYB gene variation, we identified four distinct population groups with statistical significance (FCT= 0.42; p<0.05). We identified a total of 3,013 SNPs through GBS, with 11 loci showing putative signs of being under selection. The variation based on 3,002 neutral loci evidenced low genetic structuration based on low FST values (p>0.05), indicating local panmixia. However, resampling algorithms pointed out that three samples from the external population were assigned (>98 %) in a cluster contrasting from the ones putatively under local panmixia - validating the newly applied genome-wide marker for studies on the population genetics at finer-scale resolution for T. brasiliensis. The presence of population structuring in some of the sampled points, as suggested by the mitochondrial marker, leads us to assume that infestations were probably initiated by small populations of females - demographic event poses a risk for rapid re-infestations. The local panmictic pattern revealed by the GBS marker poses a challenge for vector control measures, as re-infestation foci may be distributed over a wide geographical and ecological range. In such instances, vectors exhibit reduced susceptibility to conventional insecticide spraying operations since sylvatic populations are beyond the reach of these interventions. The pattern of infestation exhibited by T. brasiliensis necessitates integrating innovative strategies into the existing control framework, holding the potential to create a more resilient and adaptive vector control program. In our dataset, the results demonstrated that the genetic signals from both markers were complementary. Therefore, it is essential to consider the nature and inheritance pattern of each marker when inferring the pattern of re-infestations.

Effects of cattle on vector-borne disease risk to humans: A systematic review

Vector-borne pathogens (VBPs) causing vector-borne diseases (VBDs) can circulate among humans, domestic animals, and wildlife, with cattle in particular serving as an important source of exposure risk to humans. The close associations between humans and cattle can facilitate the transmission of numerous VBPs, impacting public health and economic security. Published studies demonstrate that cattle can influence human exposure risk positively, negatively, or have no effect. There is a critical need to synthesize the information in the scientific literature on this subject, in order to illuminate the various ecological mechanisms that can affect VBP exposure risk in humans. Therefore, the aim of this systematic review was to review the scientific literature, provide a synthesis of the possible effects of cattle on VBP risk to humans, and propose future directions for research. This study was performed according to the PRISMA 2020 extension guidelines for systematic review. After screening 470 peer-reviewed articles published between 1999-2019 using the databases Web of Science Core Collection, PubMed Central, CABI Global Health, and Google Scholar, and utilizing forward and backward search techniques, we identified 127 papers that met inclusion criteria. Results of the systematic review indicate that cattle can be beneficial or harmful to human health with respect to VBDs depending on vector and pathogen ecology and livestock management practices. Cattle can increase risk of exposure to infections spread by tsetse flies and ticks, followed by sandflies and mosquitoes, through a variety of mechanisms. However, cattle can have a protective effect when the vector prefers to feed on cattle instead of humans and when chemical control measures (e.g., acaricides/insecticides), semio-chemicals, and other integrated vector control measures are utilized in the community. We highlight that further research is needed to determine ways in which these mechanisms may be exploited to reduce VBD risk in humans.

Temporal assessment of entomological surveillance of Trypanosoma cruzi vectors in an endemic area of northeastern Brazil

Entomological surveillance is essential for the control of triatomines and the prevention of Trypanosoma cruzi infection in humans and domestic animals. Thus, the objective of this study was to evaluate entomological indicators and triatomine control during the period from 2005 to 2015 in an endemic area in the state of Rio Grande do Norte, Brazil. This observational and retrospective study was developed based on data analysis related to active entomological surveillance activities and chemical control of infested housing units (HU) in the Agreste mesoregion of the state of Rio Grande do Norte, Brazil, in the period between 2005 to 2015. The quantitative analysis of housing units surveyed for entomological indicators was performed by linear regression of random effects (p < 0.05). The effect of the number of HU surveyed on the entomological indicators was analyzed by fitting a linear random effects regression model and an increasing intradomiciliary colonization rate was significant. In the period evaluated 92,156 housing units were investigated and the presence of triatomines was reported in 4,639 (5.0%). A total of 4,653 specimens of triatomines were captured and the species recorded were Triatoma pseudomaculata (n = 1,775), Triatoma brasiliensis (n = 1,569), Rhodnius nasutus (n = 741) and Panstrongylus lutzi (n = 568), with an index of natural infection by T. cruzi of 2.2%. Only 53.1% of the infested HU were subjected to chemical control. Moreover, there was a decrease in the total number of HU surveyed over time associated with an increase in the index of intradomiciliary colonization (p = 0.004). These data demonstrated that entomological surveillance and control of vectors in the Agreste mesoregion of the state has been discontinued, emphasizing the need for more effective public policies to effectively control the vectors, in order to avoid the exposure of humans and domestic animals to the risk of T. cruzi infection.

Wild mammals involved in the transmission of Trypanosoma cruzi and food sources of Triatoma sherlocki in an endemic region of northeastern Brazil

The present study, carried out in the municipality of Gentio do Ouro, Bahia, Brazil aimed to evaluate which wild mammals may be involved in the transmission of T. cruzi and which are the blood sources for triatomines collected in the study area. PCR analysis of 31 wild mammals captured revealed T. cruzi infection in 6.4% (2/31): one specimen of the opossum Didelphis albiventris (1/3) and one of the rodent Kerodon rupestris (1/5); despite being more frequent in the area, no specimen of the rodent Thrichomys sp. (0/23) was infected. A total of 169 triatomines were captured. The conclusive detection of food sources was possible only for Triatoma sherlocki Papa et al., 2002 (n = 56), with evidence for: K. rupestris (35.7%), Gallus (17.9%), D. albiventris (14.3%), Homo sapiens (14.3%), Tropidurus hispidus (7.1%), Leopardus geoffroyi (5.3%), Conepatus semistriatus (1.8%), Thrichomys inermis (1.8%) and Rattus norvegicus (1.8%). Triatomines of the species T. sherlocki showed food eclecticism, including feeding on humans, with some of them being captured at dwellings. These facts make this triatomine a potential link for the transmission of T. cruzi between wild and anthropic environments, highlighting a latent risk of the reemergence of Chagas disease outbreaks.

"Mi Casa, Tu Casa": the coati nest as a hub of Trypanosoma cruzi transmission in the southern Pantanal biome revealed by molecular blood meal source identification in triatomines

BACKGROUND

The study of the ecology of Trypanosoma cruzi is challenging due to its extreme adaptive plasticity, resulting in the parasitism of hundreds of mammal species and dozens of triatomine species. The genetic analysis of blood meal sources (BMS) from the triatomine vector is an accurate and practical approach for gathering information on which wild mammal species participate in a local transmission network. South American coatis, Nasua nasua, act as important reservoir host species of T. cruzi in the Pantanal biome because of their high rate of infection and elevated parasitemia, with the main discrete typing unit (DTU) lineages (TcI and TcII). Moreover, the carnivore coati is the only mammal species to build high arboreal nests for breeding and resting that can be shared by various vertebrate and invertebrate species. Herein, we applied the sensitive and specific methodology of DNA barcoding and molecular cloning to study triatomines found in a coati nest to access the diversity of mammal species that explore this structure, and therefore, may be involved in the parasite transmission network.

METHODS

Twenty-three Triatoma sordida were collected in one coati's nest in the subregion of Nhecolândia, Pantanal. The DNA isolated from the gut of insects was subjected to BMS detection by PCR using universal primers that flank variable regions of the cytochrome b (cytb) and 12S rDNA mitochondrial genes from vertebrates. The Trypanosoma spp. diagnosis and DTU genotyping were based on an 18S rDNA molecular marker and also using new cytb gene primers designed in this study. Phylogenetic analyses and chord diagrams were constructed to visualize BMS haplotypes, DTU lineages detected on vectors, and their interconnections.

RESULTS

Twenty of 23 triatomines analyzed were PCR-positive (86.95%) showing lineages T. cruzi DTU TcI (n = 2), TcII (n = 6), and a predominance of TcI/TcII (n = 12) mixed infection. Intra-DTU diversity was observed mainly from different TcI haplotypes. Genetic analyses revealed that the southern anteater, Tamandua tetradactyla, was the unique species detected as the BMS of triatomines collected from the coati's nest. At least three different individuals of T. tetradactyla served as BMS of 21/23 bugs studied, as indicated by the cytb and 12S rDNA haplotypes identified.

CONCLUSIONS

The identification of multiple BMS, and importantly, different individuals of the same species, was achieved by the methodology applied. The study demonstrated that the southern anteaters can occupy the South American coati's nest, serving as the BMS of T. sordida specimens. Since anteaters have an individualist nonsocial behavior, the three individuals detected as BMS stayed at the coati's nest at different times, which added a temporal character to BMS detection. The TcI and TcII infection, and significantly, a predominance of TcI/TcII mixed infection profile with different TcI and TcII haplotypes was observed, due to the discriminatory capacity of the methodology applied. Tamandua tetradactyla, a host which has been little studied, may have an important role in the T. cruzi transmission in that Pantanal subregion. The data from the present study indicate the sharing of coatis' nests by other mammal species, expanding the possibilities for T. cruzi transmission in the canopy strata. We propose that coatis' nests can act as the true hubs of the T. cruzi transmission web in Pantanal, instead of the coatis themselves, as previously suggested.

Spatial analysis of the natural infection index for Triatomines and the risk of Chagas disease transmission in Northeastern Brazil

This study aimed to analyze the spatial pattern of natural infection index (NII) for triatomines and the risk of Chagas disease transmission in an endemic area of Northeastern Brazil. An ecological study was conducted, based on 184 municipalities in five mesoregions. The NII for triatomines was evaluated in the Pernambuco State, Brazil, from 2016 to 2018. Spatial autocorrelations were evaluated using Global Moran Index (I) and Local Moran Index (II) and were considered positive when I > 0 and p < 0.05, respectively. In total, 7,302 triatomines belonging to seven different species were detected. Triatoma brasiliensis had the highest frequency (53%; n = 3,844), followed by Triatoma pseudomaculata (25%; n = 1,828) and Panstrongylus lutzi (18.5%; n=1,366). The overall NII was 12%, and the higher NII values were P. lutzi (21%) and Panstrongylus megistus (18%). In the mesoregions of Zona da Mata, Agreste, Sertao, and Sertao do Sao Francisco, 93% of triatomines were detected indoors. The global spatial autocorrelation of I to NII was positive (0.2; p = 0.01), and II values calculated using BoxMap, MoranMap, Lisa Cluster Map were statistically significant for natural infections. With regard to the risk areas for the presence of triatomines, Zone 2 (the Agreste and Sertao regions) presented a relative risk of 3.65 compared to other areas in the state. Our study shows the potential areas of vector transmission of Chagas disease. In this study, the application of different methods of spatial analysis made it possible to locate these areas, which would not have been identified by only applying epidemiological indicators.

Molecular identification of Trypanosoma cruzi in domestic animals in municipalities of the State of Rio Grande do Norte, Brazil

Trypanosoma cruzi, the etiologic agent of American trypanosomiasis, is a vector-borne zoonotic parasite which has been little studied regarding its infection in domestic animals. In this study, we evaluated the occurrence of natural infection by T. cruzi in farm animals using molecular markers and phylogenetic analysis in blood clot samples of 60 sheep (Ovis aires), 22 goats (Capra hircus), and 14 horses (Equus caballus) in eight municipalities located in an infection risk area in the state of Rio Grande do Norte (RN), Northeast Region of Brazil. Trypanosoma spp. infection was identified by amplifying the rRNA 18S SSU gene in 48.9% of the samples. The SH022 sample showed 99.8% similarity with the Y strain of T. cruzi in phylogeny, grouped in the DTU II clade. Blood clots of sheep, goats, and horses detected T. cruzi kDNA in 28.3% (17/60), 22.7% (5/22), and 15.4% (2/14) of the samples, respectively. These animals were distributed in the three studied mesoregions throughout the state of RN. The identification of natural infection in domestic animals contributes to expand the epidemiological transmission scenario in an area where T. brasiliensis is the main vector.

Molecular detection of Trypanosoma cruzi in equids in a semiarid zone of Pernambuco - Brazil

Trypanosoma cruzi is the etiological agent of Chagas disease, a neglected and frequently occurring zoonosis in Central and South American countries. Wild mammals and domestic dogs are the main reservoirs of the parasite in the wild and domestic cycles, respectively. The vectors have a wide variety of food sources that can influence transmission cycles. The aim of this study was to determine the prevalence of T. cruzi infection in donkeys (Equus asininos) and mules (Equus mulus) living in rural areas of the Brazilian semi-arid region. Whole-blood samples from 72 equids (65 donkeys and 7 mules) were analyzed by nested polymerase chain reaction (nested PCR). A total of 51.39% of the samples (37/72) were positive. Phylogenetic analysis identified discrete typing units TcI and TcII, which suggested the possibility that donkeys and mules might be participating in domestic/peridomestic and wild transmission cycles. This was the first report of T. cruzi infection in donkeys and mules in Brazil, with high prevalence of positive animals. This places these animals as potential reservoirs for the parasite and the particular features of these hosts, the presence of vectors and the socioeconomic characteristics of the population under semiarid conditions create interactions that may favor transmission and overlapping T. cruzi infection cycles.

High Parasitic Loads Quantified in Sylvatic Triatoma melanica, a Chagas Disease Vector

Triatoma melanica is a sylvatic vector species in Brazil. In We aimed to characterize the Trypanosoma cruzi discrete typing units (DTUs), the parasitic loads, and the blood meal sources of insects collected in rocky outcrops in rural areas in the state of Minas Gerais. An optical microscope (OM) and kDNA-PCR were used to examine natural infection by T. cruzi, and positive samples were genotyped by conventional multilocus PCR. Quantification of the T. cruzi load was performed using qPCR, and the blood meal sources were identified by Sanger sequencing the 12S rRNA gene. A total of 141 T. melanica were captured. Of these, ~55% (61/111) and ~91% (63/69) were positive by OM and KDNA-PCR, respectively. We genotyped ~89% (56/63) of the T. cruzi-positive triatomines, with TcI (~55%, 31/56) being the most prevalent DTU, followed by TcIII (~20%, 11/56) and TcII (~7%, 4/56). Only TcI+TcIII mixed infections were detected in 10 (~18%) specimens. A wide range of variation in the parasitic loads of T. melanica was observed, with an overall median value of 10⁴ parasites/intestine, with females having higher T. cruzi loads than N2, N4, and N5. TcII showed lower parasitic loads compared to TcI and TcIII. The OM positive diagnosis odds ratio between T. cruzi infection when the parasite load is 10⁷ compared to 10³ was approximately 29.1. The most frequent blood meal source was Kerodon rupestris (~58%), followed by Thrichomys apereoides (~18%), Wiedomys cerradensis (~8%), Galactis cuja (~8%) and Gallus gallus (~8%). Our findings characterize biological and epidemiological aspects of the sylvatic population of T. melanica in the study area, highlighting the need to extend surveillance and control to this vector.

Identification of blood meal sources in species of genus Rhodnius in four different environments in the Brazilian amazon

Chagas disease is a zoonotic disease caused by the hemoflagellate Trypanosoma cruzi and transmitted primarily by triatomine vectors. Triatomines are hematophagous insects that feed on a variety of vertebrate hosts. The Chagas disease transmission cycle is closely related to the interactions between vectors, parasites, and vertebrate hosts. Knowledge of triatomine food sources is critical to understanding Chagas disease transmission dynamics. The aim of this study was to identify blood meal sources used by triatomines from different environments in the Brazilian Amazon. A total of 25 captures were conducted in four environments. Triatomine specimens were captured on palm trees and were identified by morphological and morphometric characters. Blood meal sources identification was conducted using a traditional PCR followed by Sanger sequencing of mtDNA cytb gene. Sequencing was successful in 167 specimens and a total of 21 blood meal sources were identified: two reptilians, six birds, and 13 mammals. Among these 21 species, three (Tamandua tetradactyla, Didelphis marsupialis and Rattus rattus) are considered reservoir of T. cruzi. Knowledge of the relationship between triatomines and possible reservoirs can help to elucidate the enzootic cycle of T. cruzi in the Amazon region and guide control strategies for Chagas disease transmission in that region.

Molecular characterization of Trypanosoma cruzi DTUs of the triatomine species in a Chagas disease endemic area

Trypanosoma cruzi is the etiological agent of Chagas disease, a neglected tropical infection with great public health importance. This protozoan has triatomine insects as vector but may also be transmitted through blood transfusion, organ transplants, ingestion of contaminated food, or congenitally. It has a heterogeneous population classified into Discrete Typing Units (DTUs), TcI-TcVI and TcBat. The aim of this study was to molecularly characterize the DTUs of T. cruzi in triatomines from a Chagas disease endemic area in Northeastern Brazil. Triatomines were collected and the gut content was microscopically analyzed to investigate the presence of trypanosomatid flagellates. In addition, digestive tracts of some specimens were dissected and molecularly analyzed through PCR for Trypanosoma spp. and sequencing. PCR positive samples were further submitted to a multiplex PCR for DTUs of T. cruzi. A total of 117 triatomines were collected, 93.16% being in intradomicile and 6.84% in peridomicile environments. Insects were identified as Panstrongylus lutzi (37.60%), Triatoma pseudomaculata (26.50%), Triatoma brasiliensis (23.08%) and Panstrongylus megistus (12.82%). The specimens herein analyzed presented infection rates by T. cruzi of 5.49% and 12.09% in parasitological and molecular examinations, respectively. Multiplex PCR screening revealed 70.59% of the TcI genotype, detected in all triatomine species identified in this study and 29.41% of the DTU TcIII/TcIV detected in P. megistus and P. lutzi. T. cruzi infect triatomines in intradomicile and peridomicile environments, which brings attention to the risk of human infections and to the importance of the implementation of surveillance and entomological control actions.

Chagas Disease Ecology in the United States: Recent Advances in Understanding Trypanosoma cruzi Transmission Among Triatomines, Wildlife, and Domestic Animals and a Quantitative Synthesis of Vector-Host Interactions

Chagas disease, a neglected tropical disease present in the Americas, is caused by the parasite Trypanosoma cruzi and is transmitted by triatomine kissing bug vectors. Hundreds of vertebrate host species are involved in the ecology of Chagas disease. The sylvatic nature of most triatomines found in the United States accounts for high levels of animal infections but few reports of human infections. This review focuses on triatomine distributions and animal infections in the southern United States. A quantitative synthesis of available US data from triatomine bloodmeal analysis studies shows that dogs, humans, and rodents are key taxa for feeding triatomines. Imperfect and unvalidated diagnostic tools in wildlife complicate the study of animal T. cruzi infections, and integrated vector management approaches are needed to reduce parasite transmission in nature. The diversity of animal species involved in Chagas disease ecology underscores the importance of a One Health approach for disease research and management. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 10 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The connection between Trypanosoma cruzi transmission cycles by Triatoma brasiliensis brasiliensis: A threat to human health in an area susceptible to desertification in the Seridó, Rio Grande do Norte, Brazil

An outbreak of Chagas disease, possibly involving its vector Triatoma brasiliensis brasiliensis, was identified in the state of Rio Grande do Norte (RN). Given the historical significance of this vector in public health, the study aimed to evaluate its role in the transmission dynamics of the protozoan Trypanosoma cruzi in an area undergoing desertification in the Seridó region, RN, Brazil. We captured triatomines in sylvatic and anthropic ecotopes. Natural vector infection was determined using parasitological and molecular methods and we identified discrete typing units (DTUs) of T. cruzi by analyzing the COII gene of mtDNA, 24Sα rDNA, and mini-exon gene. Their blood meals sources were identified by amplification and sequencing of the mtDNA cytochrome b gene. A total of 952 T. b. brasiliensis were captured in peridomestic (69.9%) and sylvatic ecotopes (30.4%). A wide range of natural infection rates were observed in peridomestic (36.0% - 71.1%) and sylvatic populations (28.6% - 100.0%). We observed the circulation of TcI and TcII DTUs with a predominance of Tcl in sylvatic and peridomestic environments. Kerodon rupestris, rocky cavy (13/39), Homo sapiens, human (8/39), and Bos taurus, ox (6/39) were the most frequently detected blood meals sources. Thus, Triatoma b. brasiliensis is invading and colonizing the human dwellings. Furthermore, high levels of natural infection, coupled with the detection of TcI and TcII DTUs, and also the detection of K. rupestris and H. sapiens as blood meals sources of infected T. b. brasiliensis indicate a risk of T. cruzi transmission to human populations in areas undergoing desertification.

Chagas disease currently affects about six to seven million people worldwide, resulting in high morbidity, mortality, and economic burden in endemic countries of Latin America. Its etiological agent, Trypanosoma cruzi, circulates among a wide variety of mammalian and insect vectors. Triatoma brasiliensis brasiliensis is adapted to the dry and warm climate of the Caatinga biome, and is considered the main vector in the semi-arid areas of northeastern Brazil. Information on the infestation, natural infection rates, T. cruzi strains, and blood meals sources of this vector is crucial for understanding the dynamics of T. cruzi transmission in areas susceptible to desertification. Triatoma b. brasiliensis colonizes peridomestic structures, particularly in the stone walls of cattle corrals that emerge as a refuge for sylvatic populations where they access a variety of blood meals sources. The predominance of the TcI strain in the sylvatic and peridomestic environments shows an overlap of transmission cycles by T. cruzi mediated by T. b. brasiliensis. The high rates of natural infection and the evidence of their feeding on humans and the rodent K. rupestris are worrisome and indicate the threat this vector poses to human health in the area studied.

Host Bloodmeal Source Has No Significant Effect on the Fecundity and Subsequent Larval Development Traits of the Progeny in Culicoides furens Poey (Diptera: Ceratopogonidae)

Culicoides Latreille species (Diptera: Ceratopogonidae) are insects of significant medical and veterinary importance worldwide because their bites can cause major annoyance, allergic reactions, and/or pathogen transmission to vertebrates, including humans. In this study, we examined the effect of host bloodmeal source on the fecundity and subsequent larval development traits of the progeny of Culicoides furens Poey, a nuisance species in coastal Florida. Field-collected females were fed on two different classes of hosts: birds (chicken) or mammals (human). Fecundity outcomes of the females and larval developmental traits of the progeny were recorded and compared between the two groups. The percentage of females that developed eggs, percentage of gravid females that deposited eggs, number of eggs produced per female, number of eggs deposited per female, egg hatch rates, larval survival rates, time to pupation, pupal sex-ratios, and adult eclosion rates were not significantly different between the two groups. Our results demonstrate that the host bloodmeal source has no significant effect on the fecundity and subsequent larval developmental life-history traits of the progeny in C. furens. Previous studies reported C. furens to be a generalist feeder that shows no host preference for birds or mammals. Collectively, these findings suggest that C. furens is well adapted, not just behaviorally, but also physiologically to efficiently utilize blood meals from avian and mammalian hosts, a quality that offers a major evolutionary advantage to the success of this midge species as a generalist feeder.

Genotypic Trypanosoma cruzi distribution and parasite load differ ecotypically and according to parasite genotypes in Triatoma brasiliensis from endemic and outbreak areas in Northeastern Brazil

This study aimed to identify the Trypanosoma cruzi genotypes and their relationship with parasitic load in distinct geographic and ecotypic populations of Triatoma brasiliensis in two sites, including one where a Chagas disease (ChD) outbreak occurred in Rio Grande do Norte state, Brazil. Triatomine captures were performed in peridomestic and sylvatic ecotopes in two municipalities: Marcelino Vieira - affected by the outbreak; and Currais Novos - where high pressure of peridomestic triatomine infestation after insecticide spraying have been reported. The kDNA-PCR was used to select 124 T. cruzi positive triatomine samples, of which 117 were successfully genotyped by fluorescent fragment length barcoding (FFLB). Moreover, the T. cruzi load quantification was performed using a multiplex TaqMan qPCR. Our findings showed a clear ecotypic segregation between TcI and TcII harboured by T. brasiliensis (p<0.001). Although no genotypes were ecotypically exclusive, TcI was predominant in peridomestic ecotopes (86%). In general, T. brasiliensis from Rio Grande do Norte had a higher T. cruzi load varying from 3.94 to 7.66 x 10⁶T. cruzi per insect. Additionally, TcII (median value=299,504 T. cruzi/intestine unit equivalents) had more than twice (p=0.1) the parasite load of TcI (median value=149,077 T. cruzi/intestine unit equivalents), which can be attributed to a more ancient co-evolution with T. brasiliensis. The higher prevalence of TcII in the sylvatic T. brasiliensis (70%) could be associated with a more diversified source of bloodmeals for wild insect populations. Either TcI or TcII may have been responsible for the ChD outbreak that occurred in the city of Marcelino Vieira. On the other hand, a smaller portion of T. brasiliensis was infected by TcIII (3%) in the peridomicile, in addition to T. rangeli genotype A (1%), often found in mixed infections. Our results highlight the need of understanding the patterns of T. cruzi genotype´s development and circulation in insect vectors and reservoirs as a mode of tracking situations of epidemiologic importance, as the ChD outbreak recently recorded for Northeastern Brazil.

Triatomine and Trypanosoma cruzi discrete typing units distribution in a semi-arid area of northeastern Brazil

The occurrence of triatomine species, their bloodmeal sources and the discrete typing units (DTUs) of Trypanosoma cruzi isolated from them were determined in different municipalities of the state of Rio Grande do Norte, Brazil. Triatomine captures were carried out in the rural areas of 23 municipalities. The genotyping of T. cruzi isolates was performed using the mitochondrial cytochrome c oxidase subunit 2 (coii) gene, the D7 region of the 24Sα rDNA, and the spliced leader intergenic region (SL-IR). Five triatomine species were captured, and the most frequent was Triatoma brasiliensis (84.3%; 916/1086), which was found in 16 of the 23 municipalities surveyed, and infested all types of environment investigated. The TcI DTU was found in all mesoregions surveyed in 51.5% (17/33) of the culture-positive samples. In contrast, TcII (9.1%; 3/33) was detected in the Central mesoregion, while TcIII (27.3%; 9/33) was found in all mesoregions. The geographic distribution and spatial overlap of different DTUs was inferred using the superposition of the radius of occurrence of isolates and using ecological niche distribution modelling. Triatoma brasiliensis was found infected in all mesoregions and with all three T. cruzi DTUs, including mixed infections. With regard to bloodmeal sources, the DNA of rodents was found in triatomines infected with either TcI or TcIII, while that of domestic animals and humans was associated with both single and mixed infections. Our findings demonstrate that different DTUs of T. cruzi are widely dispersed among triatomines in our study area. The association of T. brasiliensis with several different mammalian hosts, as well as overlapping areas with different DTUs, suggests that this triatomine species may have an important role as a vector in both anthropic and sylvatic environments.

Drivers of molecular and morphometric variation in Triatoma brasiliensis (Hemiptera: Triatominae): the resolution of geometric morphometrics for populational structuring on a microgeographical scale

Background

The protozoan Trypanosoma cruzi circulates in semiarid areas of northeastern Brazil in distinct ecotopes (sylvatic, peridomestic and domestic) where Triatoma brasiliensis Neiva, 1911 is the most important Chagas disease vector. In this study, we analyzed microevolutionary and demographic aspects of T. brasiliensis populations at the ecotypic, micro and macro-geographic scales by combining morphometrics and molecular results. Additionally, we aimed to address the resolution of both markers for delimiting populations in distinct scales.

Methods

We sampled populations of T. brasiliensis from distinct ecotypic and geographic sites in the states Rio Grande do Norte (RN) and Paraíba (PB). The geometric morphometry was carried out with 13 landmarks on the right wings (n = 698) and the genetic structure was assessed by sequencing a region of cytochrome b mitochondrial gene (n = 221). Mahalanobis distance (MD) and coefficient of molecular differentiation (Φ_ST) were calculated among all pairs of populations. The results of comparisons generated MD and Φ_ST dendrograms, and graphics of canonical variate analysis (CVA).

Results

Little structure was observed for both markers for macro-geographic scales. Mantel tests comparing geographic, morphometric and genetic matrices showed low correlation (all R² < 0.35). The factorial graphics built with the CVA evidenced population delimitation for the morphometric data at micro-geographic scales.

Conclusions

We believe that T. brasiliensis carries in its genotype a source of information to allow the phenotypical plasticity across its whole distribution for shaping populations, which may have caused a lack of population delimitation for CVAs in morphometric analysis for macro-geographic scale analysis. On the other hand, the pattern of morphometric results in micro-geographic scales showed well-defined groups, highlighting the potential of this tool to inferences on the source for infestation.

Dynamics of food sources, ecotypic distribution and Trypanosoma cruzi infection in Triatoma brasiliensis from the northeast of Brazil

Innovative approaches used to combat Chagas disease transmission tend to combine a set of comprehensive efforts to understand the ecology of local vectors. In this work we identified molecularly the blood meal of 181 Triatoma brasiliensis, distributed in 18 populations (8 sylvatic and 10 peridomestic), which were collected across a range of 240 km (East-West) and 95 km (North-South) in the semi-arid region of northeastern, Brazil. We used the vertebrate mitochondrial gene (cytochrome B) sequencing applied to DNA isolated from bug midgut to identify the insect blood meal sources via the BLAST procedure. The peridomestic populations were classified according to two main hypotheses of site-occupancy for T. brasiliensis: the first says that the infestation is mainly driven by structures that resemble its natural habitat (stony-like ecotopes) and the second assumes that it is associated with key-hosts (rodents and goats). Rodents of the Caviidae family (Galea spixii and Kerodon rupestris) were identified as the key-host of T. brasiliensis, but also the potential Trypanosoma cruzi reservoir-able to connect the sylvatic and domestic T. cruzi cycle. Cats also deserve to be studied better, as potential T. cruzi reservoirs. By modeling the food sources + site-occupancy + T. cruzi natural infection, we identified man-made ecotopes suitable for forming dense triatomine infestations with high rates of T. cruzi natural infection, which may be taken into account for vector control measures.

Spatial distribution of synanthropic triatomines in Piaui State, Northeastern Brazil

This study aimed to describe the spatial distribution and assess entomological indicators of synanthropic triatomines in Piaui State, Northeastern Brazil. We used surveillance data on the detection, identification and assessment of natural infection with trypanosomatids from triatomines in the State from 2014 to 2017. The State was divided into four macroregions. In relation to the dispersion rates of triatomines, they were much lower in the North, when compared to Southwest, Southeast and Central North macroregions. Infestation rates were higher in the Southwest and Southeast and intradomicile infestation rates varied during the study period, reaching high values in all regions. Insects belonging to the species Triatoma brasiliensis complex, Triatoma pseudomaculata, Triatoma sordida, and to the genus Panstrongylus spp. and Rhodnius spp. were collected during this period. T. brasiliensis was collected from all four regions of the State, but more frequently in those located in the Southeast. A similar pattern was observed for T. pseudomaculata. T. sordida was detected in the municipalities in the Southeast and Southwest regions, and less frequently in the Central North municipalities. Rhodnius spp. was detected in the Central North and North regions, and Panstrongylus spp. in the Central North and Southeast regions. The highest trypanosomatid-positivity rate of T. brasiliensis and Panstrongylus spp. was in the Southeast region. A significant proportion of the municipalities of Piaui State presents entomological parameters that indicate a risk of Chagas disease by vector transmission.

Fast recovery of house infestation with Triatoma brasiliensis after residual insecticide spraying in a semiarid region of Northeastern Brazil

The northeastern semiarid region stands out in the Brazilian context regarding the eco-epidemiology of Chagas disease, in which Triatoma brasiliensis is the main vector of Trypanosoma cruzi. Persistent house invasion threatens the relative levels of progress achieved over previous decades. We conducted an intervention trial with a five-year follow-up to assess the impacts of residual spraying with pyrethroid insecticides on house infestation with T. brasiliensis in 18 rural villages (242 houses) located in the Tauá, Ceará. House infestations were assessed by systematic manual searches for triatomines in every domestic and peridomestic habitat on five occasions. Triatomines were collected in peridomestic (57.5%), sylvatic (35.8%), and intradomiciliary (6.7%) habitats. The most important ecotopes of T. brasiliensis were containing roofing tiles, bricks or rocks (23.4% ± 9.1). Residual insecticide spraying substantially reduced baseline house infestation rates from 27.9% to 5.9% by 6 months post first spraying (MPS). The decline was substantially greater in intradomiciles (11.2% to 0.8%) than in peridomiciles (16.7% to 5%). The mean relative density of triatomines recovered its preintervention values at 14 MPS in intradomiciles, and in the main peridomestic ecotopes. The house infestation levels recorded at 14 MPS persisted thereafter despite all reinfested houses were selectively sprayed on every occasion. Overall average bug infection rates with T. cruzi in the five occasions were in intradomiciles (11.1%), peridomiciles (4.7%) and wild habitats (3.3%). In peridomicile T. cruzi infection rates decreased significantly at all stages after chemical intervention. In intradomicile, the only significant difference occurred at 20 MPS (7.7% to 30.8%). The vectorial capacity of T. brasiliensis, combined with its invasive potential from sylvatic sources and the limited effectiveness of chemical control in the harsh caatinga landscape, pose serious obstacles to the definite elimination of domestic transmission risks. Systematic vector surveillance supported by community participation and locally adapted environmental management measures are needed to reduce the risks of establishment of domestic transmission with T. cruzi in this region.

The results demonstrate the ecological potential of Triatoma brasiliensis in the northeastern caatinga and how this species uses the resources available in nature or in the modified environment by man. Triatomines were collected in peridomestic, sylvatic, and intradomicile habitats. House infestations were evaluated on five occasions, with spraying of infested houses. T. brasiliensis was responsible for the high rates of dispersal, infestation, colonization and Trypanosoma cruzi infection in all catches and environments studied here. Spraying strongly reduced the infestation, but the number of triatomines rapidly returned to previous levels. Peridomicile represents a complex set of overlapping infested sites forming a network of shelters that favor the establishment and proliferation of triatomine colonies. Molecular characterization of T. cruzi isolated from triatomines and identification of their food sources emphasize the overlap of habitats and interaction among triatomines, synanthropic reservoirs and humans, increasing the risk of parasite transmission. Therefore, it is clear the need for maintenance of vector control fully and systematically with the use of appropriate strategies where interventions should consider regional ecoepidemiologic differences and the influence of environmental, socioeconomic and cultural factors in T. cruzy transmission process into domicile environment.

Triatoma petrocchiae (Hemiptera, Reduviidae, Triatominae): A Chagas disease vector of T. brasiliensis species complex associated to reptiles

In semi-arid areas of northeastern Brazil, Chagas disease vectors of Triatoma brasiliensis species complex comprise a monophyletic group of kissing bugs that inhabit rock outcrops. Most of them exhibit allopatric or parapatric distribution; the exception is T. petrocchiae, which is found in cohabitation with T. brasiliensis in rock outcrops. We used vertebrate mitochondrial gene sequencing applied to DNA isolated from bug midgut to identify the insect blood meal sources via BLAST procedure. Fourteen sylvatic insects from four geographic districts in the states of Rio Grande do Norte and Paraíba had their blood meal sources detected. While T. brasiliensis is recorded to be associated mainly (52-71%) with rodents, T. petrocchiae samples were strongly associated (86%) with reptiles of Tropidurus and Hemidactylus genera. We suggest that T. petrocchiae is the single member within this complex to be associated with reptiles, indicating a distinct niche occupation related to the trophic resources.

Molecular eco-epidemiology on the sympatric Chagas disease vectors Triatoma brasiliensis and Triatoma petrocchiae: Ecotopes, genetic variation, natural infection prevalence by trypanosomatids and parasite genotyping

Triatoma petrocchiae is the newly member of the Triatoma brasiliensis species complex. This species overlaps with T. brasiliensis in geographic and ecotypic occupation in the sylvatic habitat because both inhabit rocky outcrops in the semi-arid portion of Brazilian northeast. In this region T. brasiliensis is the most important Chagas disease vector because it constantly colonizes domiciles. In contrast, T. petrocchiae is rarely found in peri or intradomiciliary habitats - reason why little is known about this species. Therefore, Here, we present information for the first time on. the T. petrocchiae ecotopes, genetic diversity, Trypanosoma cruzi prevalence/genotyping in comparison to T. brasiliensis. We found T. brasilensis (N = 223) and T. petrocchiae (N = 69) in co-habitation in rocky outcrops in three Districts of Paraíba and Rio Grande do Norte states. Forty-tree T. petrocchiae insects of eleven sampling spots (composing three geographic populations) were genotyped for the mitochondrial Cyt B gene and little geographic structure was observed. Tajima's D test suggested that species is evolving toward a mutation-drift equilibrium in our collection range. Sylvatic T. petrocchiae had 4% (3/68) of infected insects by T. cruzi, whereas T. brasiliensis had 26% (59/223). Fluorescent Fragment Length Barcoding demonstrated that all three T. petrocchiae harbored TcI whereas T. brasiliensis had TcI, but also TcIII, TcII/TcVI and T. rangeli genotype A, sometimes under mixed infections. None of infected T. petrocchiae were carrying mixed infections. However, this result should be confirmed using a larger pool of infected bugs. We here presented the first documentation of T. rangeli infecting T. brasiliensis. The finding of infected T. petrocchiae calls for constant vector monitoring because the epidemiologic scenario is dynamic and sylvatic vectors are progressively found in adaptation to anthropic environments.

Wide distribution of Trypanosoma cruzi-infected triatomines in the State of Bahia, Brazil

Background

The identification of Trypanosoma cruzi and blood-meal sources in synanthropic triatomines is important to assess the potential risk of Chagas disease transmission. We identified T. cruzi infection and blood-meal sources of triatomines caught in and around houses in the state of Bahia, northeastern Brazil, and mapped the occurrence of infected triatomines that fed on humans and domestic animals.

Methods

Triatominae bugs were manually captured by trained agents from the Epidemiologic Surveillance team of Bahia State Health Service between 2013 and 2014. We applied conventional PCR to detect T. cruzi and blood-meal sources (dog, cat, human and bird) in a randomized sample of triatomines. We mapped triatomine distribution and analyzed vector hotspots with kernel density spatial analysis.

Results

In total, 5906 triatomines comprising 15 species were collected from 127 out of 417 municipalities in Bahia. The molecular analyses of 695 triatomines revealed a ~10% T. cruzi infection rate, which was highest in the T. brasiliensis species complex. Most bugs were found to have fed on birds (74.2%), and other blood-meal sources included dogs (6%), cats (0.6%) and humans (1%). Trypanosoma cruzi-infected triatomines that fed on humans were detected inside houses. Spatial analysis showed a wide distribution of T. cruzi-infected triatomines throughout Bahia; triatomines that fed on dogs, humans, and cats were observed mainly in the northeast region.

Conclusions

Synanthropic triatomines have a wide distribution and maintain the potential risk of T. cruzi transmission to humans and domestic animals in Bahia. Ten species were recorded inside houses, mainly Triatoma sordida, T. pseudomaculata, and the T. brasiliensis species complex. Molecular and spatial analysis are useful to reveal T. cruzi infection and blood-meal sources in synanthropic triatomines, identifying areas with ongoing threat for parasite transmission and improving entomological surveillance strategies.

Enduring extreme climate: Effects of severe drought on Triatoma brasiliensis populations in wild and man-made habitats of the Caatinga

Background

Triatoma brasiliensis, a triatomine-bug vector of Chagas disease, evolved in the semiarid Caatinga, where it occupies rocky outcrops, shrubby cacti, and human dwellings. Dwellings and rocks are considered high-quality microhabitats for this saxicolous species, whereas cacti probably represent secondary, lower-quality microhabitats. This ‘microhabitat-quality hierarchy’ hypothesis predicts that T. brasiliensis populations occupying dwellings or rocks should endure harsh environmental conditions better than their cactus-living relatives.

Methods/Findings

We tested this prediction by comparing T. brasiliensis infestation (proportion of microhabitats with bugs), density (bugs per microhabitat), and crowding (bugs per infested microhabitat) in dwellings, rocks, and cacti sampled before and during the extreme drought that ravaged the Caatinga in 2012–2016. We used random-intercepts generalized linear mixed models to account for microhabitat spatial clustering and for variations in bug-catch effort; we assessed model performance and computed model-averaged effect estimates using Akaike’s information criterion. Pre-drought infestation was similar across microhabitat types; during the drought, infestation remained stable in dwellings and rocks but dropped in cacti. Pre-drought bug density declined from dwellings to rocks to cacti; an additional decline associated with the drought was largely comparable across microhabitats, albeit perhaps somewhat larger in cacti. Finally, pre-drought bug crowding was higher in dwellings than in rocks or cacti and changed little during the drought–possibly with a downward trend in dwellings and an upward trend in cacti.

Conclusions

Triatoma brasiliensis populations fared better in dwellings and rocks than in cacti during extreme drought. Estimates of microhabitat and drought effects on infestation, density, and crowding suggest that only a few cacti (versus many rocks and dwellings) represent good-quality habitat under such extremely harsh conditions. Our findings provide empirical support to the microhabitat-quality hierarchy hypothesis, and imply that T. brasiliensis can endure extreme climate by exploiting high-quality microhabitats, whether wild or man-made, in the semiarid Caatinga.

Triatomine bugs, the vectors of Chagas disease, feed on vertebrate blood and occupy diverse microhabitats in close association with their hosts. Each bug species is adapted to particular, ‘primary’ microhabitats. Many species, however, also use ‘secondary’ microhabitats, sometimes including man-made structures. Secondary wild microhabitats are probably of lower overall quality than primary microhabitats, whereas human dwellings can be of higher overall quality if they provide a stable and abundant blood supply. This suggests that there may be a ‘hierarchy’ of triatomine microhabitat quality–top-quality dwellings, high-quality primary microhabitats, and low-quality secondary wild microhabitats. To test this hypothesis, we measured the impact of a severe drought on Triatoma brasiliensis populations living in dwellings and wild habitats, both primary (rocks) and secondary (shrubby cacti). Dwelling and rock bug populations remained largely stable during the drought, whereas most cactus-living populations either became extinct or shrunk to an undetectable size. A few cacti, however, supported relatively large bug colonies even during the drought, suggesting that they were of higher-than-average quality. Our findings provide support to the microhabitat-quality hierarchy hypothesis, and show that T. brasiliensis (and perhaps other triatomines) can endure extreme climate by exploiting (natural or man-made) high-quality microhabitats.