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Triatomines of the species Triatoma sherlocki are considered sylvatic; however, household invasion appears imminent, potentially carrying Trypanosoma cruzi, the causative agent of Chagas disease. The aim of this study was to report the first occurrence of a colony of T. sherlocki infected by T. cruzi in a subsistence pig farm. Triatomines collected underwent polymerase chain reaction (PCR) technique for T. cruzi detection and determination of blood meal source. The 19 triatomines collected in the pig farm were of the species T. sherlocki, comprising 26.3% nymphs (5/19), 52.6% males (10/19) and 21.1% females (4/19). PCR showed that 15.8% (3/19) of triatomines were infected by T. cruzi. The only detected blood meal source in triatomines (n = 11) was the domestic mammal Sus scrofa, commonly known as domestic pig, indicating that T. sherlocki is an opportunist, feeding on available vertebrates in the environment, including domestic animals such as pigs. These results highlight the possibility of domiciliation of the species T. sherlocki and its potential role in bridging the transmission of T. cruzi between sylvatic and domestic environments.

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Trypanosoma cruzi, the causative agent of Chagas disease (American trypanosomiasis), is a highly complex zoonosis that is present throughout South America, Central America, and Mexico. The transmission of this disease is influenced by various factors, including human activities like deforestation and land use changes, which may have altered the natural transmission cycles and their connection to the environment. In this study conducted in the Argentine Chaco region, we examined the transmission dynamics of T. cruzi by collecting blood samples from wild and domestic animals, as well as triatomine bugs from human dwellings, across five sites of varying anthropic intervention. Samples were analyzed for T. cruzi infection via qPCR, and we additionally examined triatomines for bloodmeal analysis via NGS amplicon sequencing. Our analysis revealed a 15.3% infection rate among 20 wild species (n = 123) and no T. cruzi presence in 9 species of domestic animals (n = 1359) or collected triatomines via qPCR. Additionally, we found chicken (34.28%), human (21.59%), and goat (19.36%) as the predominant bloodmeal sources across all sites. These findings suggest that anthropic intervention and other variables analyzed may have directly impacted the spillover dynamics of T. cruzi's sylvatic cycle and potentially reduced its prevalence in human habitats.

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The control of triatomine vectors depends almost exclusively on conventional insecticides. These compounds can, nevertheless, cause negative effects on environmental and human health as well as induce resistance in triatomines. Therefore, we need to look for more sustainable alternatives. Triatoma pallidipennis is one of the main chagasic vectors in Mexico. We evaluated the insecticidal effectiveness of two oils (neem and cinnamon), and two desiccants (potassium salts of fatty acids and diatomaceous earth), on 3rd instar nymphs of T. pallidipennis. The laboratory test involved direct exposure of the treatments to the insects. We found that diatomaceous earths caused 80 % mortality of nymphs after 30 days. Meanwhile, the cumulative mortality for the other treatments did not exceed 50 %. When applied to inert surfaces, the powder formulation of diatomaceous earth demonstrated greater effectiveness than the aqueous suspension. Thus, diatomaceous earth could be a promising alternative for an environmentally friendly control of triatomines.

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Aggregation is one of the most remarkable behaviours in the animal kingdom-a process that is usually governed by pheromones. Triatomines are blood-sucking bugs that act as vectors of Trypanosoma cruzi, the etiological agent of Chagas disease in mammals, including humans. Triatomines usually gather in roosting refuges by using aggregation pheromones of unknown chemical structure. In terms of vector control, one option to reduce triatomine-human contact is via capturing the insects into traps baited with lures based on such aggregation pheromones. As a first step towards this aim, we elucidated the aggregation pheromone in the triatomine Triatoma pallidipennis, using T. cruzi-infected and non-infected bugs. We used different extraction techniques and gas chromatography coupled to mass spectrometry for the identification. Also, two different bioassays were implemented for evaluating the attractant and arrestant activity of the pheromone. We found that T. pallidipennis produced short-chain aldehydes as attractants, and nitrogen-derived compounds as arrestants. We detected differences in the production and perception of these compounds according to whether animals were infected or not. These findings show that T. cruzi may influence triatomine chemical ecology and are promising tools for triatomine control.

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Chagas disease is one of the most significant vector-borne diseases in Mexico. The presence of "sylvatic" triatomine vectors of Trypanosoma cruzi (Chagas) inside human dwellings necessitates estimating their vectorial capacity. To estimate this capacity in Triatoma protracta nahuatlae (Ryckman), Triatoma sinaloensis (Ryckman), and their laboratory hybrids, 6 biological parameters were examined. Triatoma sinaloensis exhibited the shortest development time (155 days), with a median of 12 blood meals. Mortality rates varied from 35% to 45% in the 3 studied cohorts. All 3 cohorts were aggressive, initiating feeding within 0.5-1 min, and had similar feeding periods ranging from 10 to 18 min. A majority (75.3-97.9%) of the hybrids defecated when feeding, immediately after feeding, or in less than 1 min post-feeding. In contrast, only 7-42% of nymphs of T. sinaloensis defecated during the same period. Our results regarding the 6 parameters studied confirm the potential role of T. p. nahuatlae as an efficient vector of T. cruzi. Triatoma sinaloensis, on the other hand, exhibited limited vectorial capacity primarily due to its poor defecation behavior. Continued surveillance of these "sylvatic" triatomine populations is necessary to prevent an epidemiological problem.

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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.

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The hematophagous insect Mepraia spinolai (Hemiptera: Reduviidae: Triatominae) is naturally infected with the protozoan parasite Trypanosoma cruzi, the agent of Chagas disease in humans. In this study, we compared the demographic parameters of M. spinolai with and without T. cruzi infection. We collected the immature life table data of 479 M. spinolai individuals of control cohort (reared on mice without T. cruzi infection) and 563 M. spinolai individuals of treatment cohort (reared on mice with T. cruzi infection). Nymphs were maintained in individual compartments inside a growth chamber (26°C; 65-75%) until adult emergence; moulting and survival were recorded daily. For the adult life table study of the control, we used 24 pairs of adults from the control cohort. For the adult life table study of T. cruzi-infected cohort, 25 infected females were paired with 25 males from the control cohort. Life table data were analysed using bootstrap-match technique based on the age-stage, two-sex life table. The preadult survival rate (0.5282) of the control cohort was significantly higher than that of the infected cohort (0.2913). However, the mean fecundity of reproductive females (Fr = 22.29 eggs/♀) and net reproductive rate of population (R0 = 5.07 offspring/individual) of the 0.5th percentile bootstrap-match control cohort were not significantly different from those of the infected cohort (Fr = 23.35 eggs/♀, R0 = 3.77 offspring/individual). Due to the shorter total preoviposition period and higher proportion of reproductive female, the intrinsic rate of increase (r = 0.0053 d-1 ) and finite rate of increase (λ = 1.0053 d-1 ) of control cohort of M. spinolai were significantly higher than those of the T. cruzi-infected cohort (r = 0.0035 d-1 , λ = 1.0035 d-1 ). These results suggest that T. cruzi infection reduces the population fitness of the Chagas disease vector M. spinolai.

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ABSTRACT Background: Chagas disease, a zoonosis transmitted mainly by hematophagous insects of the subfamily Triatominae, is caused by Trypanosoma cruzi, classified into six discrete typing units (DTUs: TcI-TcVI and Tcbat). Methods: Insect vectors were collected from 84 human dwellings in the municipality of Santo Domingo Tehuantepec, Oaxaca, Mexico; 4.76% were infested. DTUs were determined using conventional and nested PCR. Results: The infection rate was 43.6%. All insects were infected with TcI while one specimen showed mixed infection with TcII. Conclusions: This is the first report of T. cruzi mixed infection in Triatoma phyllosoma, its main vector in the study region.

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ABSTRACT Background: Domiciliation by Triatoma sordida is a public health concern in South America. This study aimed to evaluate the morphometric changes in the domestic and peridomestic populations of T. sordida. Methods: Specimen hemelytra were mounted, digitized, and processed for geometric morphometric analyses. Results: The specimens captured in houses were smaller than those captured in peridomiciles. A large size reduction effect was observed in female peridomicile populations compared with female house populations. Conclusions: T. sordida house populations were smaller than peridomestic populations. Wing geometric morphometry can be used as a tool to indicate T. sordida domiciliation.

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BACKGROUND: Hybridization events between Triatoma spp. have been observed under both natural and laboratory conditions. The ability to produce hybrids can influence different aspects of the parent species, and may even result in events of introgression, speciation and extinction. Hybrid sterility is caused by unviable gametes (due to errors in chromosomal pairing [meiosis]) or by gonadal dysgenesis (GD). All of the triatomine hybrids analyzed so far have not presented GD. We describe here for the first time GD events in triatomine hybrids and highlight these taxonomic and evolutionary implications of these events. METHODS: Reciprocal experimental crosses were performed between Triatoma longipennis and Triatoma mopan. Intercrosses were also performed between the hybrids, and backcrosses were performed between the hybrids and the parent species. In addition, morphological and cytological analyzes were performed on the atrophied gonads of the hybrids. RESULTS: Hybrids were obtained only for the crosses T. mopan♀ × T. longipennis♂. Intercrosses and backcrosses did not result in offspring. Morphological analyses of the male gonads of the hybrids confirmed that the phenomenon that resulted in sterility of the hybrid was bilateral GD (the gonads of the hybrids were completely atrophied). Cytological analyses of the testes of the hybrids also confirmed GD, with no germ cells observed (only somatic cells, which make up the peritoneal sheath). CONCLUSIONS: The observations made during this study allowed us to characterize, for the first time, GD in triatomines and demonstrated that gametogenesis does not occur in atrophied gonads. The characterization of GD in male hybrids resulting from the crossing of T. mopan♀ × T. longipennis♂ highlights the importance of evaluating both the morphology and the cytology of the gonads to confirm which event resulted in the sterility of the hybrid: GD (which results in no gamete production) or meiotic errors (which results in non-viable gametes).

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Chagas disease is a vector-borne disease caused by Trypanosoma cruzi, which is transmitted by triatomine insects. Triatoma infestans is one of the main vectors. Efforts to eliminate T. infestans have often failed in the Gran Chaco, the largest endemic area of this species. Known methods for assessing triatomine house infestation include timed-manual collections by skilled personnel, bug notifications by householders' and/or non-baited detection devices. However, the detection sensitivity of those methods needs to be improved, especially when the bugs are present at low densities. In this work we design and evaluate the performance of two types of sticky traps (pitfall and climbing traps), when baited with a synthetic host odor lure, to capture T. infestans nymphs within an experimental box under semi-controlled laboratory conditions. Nine assays were conducted for each type of trap using a different experimental box per type of trap design and per treatment. These treatments were: test (T, trap baited with the synthetic lure), positive control (C+, trap baited with a mouse) and negative control (C-, empty trap). One hundred percent of the sticky pitfall and 89% of the climbing traps baited with the synthetic lure captured at least one insect. Moreover, the sticky pitfall trap and the sticky climbing trap, both baited with the synthetic lure, captured 30% and 40% of the insects in a single night, respectively. In both cases, the trap with the synthetic lure captured significantly more insects than the non-baited trap. However, the synthetic lure could be improved, as the traps with this lure captured significantly less insects than the traps with a live host. In summary, the two types of synthetically-baited traps tested were able to capture T. infestans nymphs, indicating that both designs are effective under the laboratory experimental conditions and insect abundance used in this work. These traps deserve to be tested in a field setting.

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Chemical control plays a central role in interrupting the vector transmission of Chagas disease. In recent years, high levels of resistance to pyrethroids have been detected in the main vector Triatoma infestans, which were associated with less effectiveness in chemical control campaigns in different regions of Argentina and Bolivia. The presence of the parasite within its vector can modify a wide range of insect physiological processes, including toxicological susceptibility and the expression of resistance to insecticides. This study examined for the first time the possible effects of Trypanosoma cruzi infection on susceptibility and resistance to deltamethrin in T. infestans. Using WHO protocol resistance monitoring assays, we exposed resistant and susceptible strains of T. infestans, uninfected and infected with T. cruzi to different concentrations of deltamethrin in fourth-instar nymphs at days 10-20 post-emergence and monitored survival at 24, 48, and 72 h. Our findings suggest that the infection affected the toxicological susceptibility of the susceptible strain, showing higher mortality than uninfected susceptible insects when exposed to both deltamethrin and acetone. On the other hand, the infection did not affect the toxicological susceptibility of the resistant strain, infected and uninfected showed similar toxic responses and the resistance ratios was not modified. This is the first report of the effect of T. cruzi on the toxicological susceptibility of T. infestans and triatomines in general and, to our knowledge, one of the few on the effect of a parasite on the insecticide susceptibility of its insect vector.

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The blood-sucking bug Triatoma infestans is the main Chagas disease vector in the Southern Cone of Latin America. Populations resistant to pyrethroid insecticides have been detected in the early 2000s and then expanded to the endemic area of northern Salta province, Argentina. In this context, the entomopathogenic fungus Beauveria bassiana has been shown to be pathogenic to pyrethroid-resistant T. infestans. In this study, both the bioinsecticidal activity and the residual effect of an alginate-based microencapsulation of a native strain of B. bassiana (Bb-C001) were tested under semi-field conditions against pyrethroid-resistant T. infestans nymphs. Fungal microencapsulated formulation caused higher nymph mortality than the unmicroencapsulated fungus and contributed to maintaining the conidial viability throughout the period evaluated under the tested conditions. These results suggest that alginate microencapsulation is an effective, simple, low-cost method that could be incorporated into the formulation of a bioinsecticide as a strategy to reduce the vector transmission of Chagas disease.

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Triatoma pallidipennis is an exclusive and widely distributed species in Mexico and one of the three main vectors that transmit Chagas disease in the country. The state of Hidalgo is an endemic area for Chagas disease where the presence of several species of triatomines has been reported. The objective of our work was to describe the morphology, colonization process, and reproductive behavior of T. pallidipennis in Guadalupe, Tecozautla, two years after the first collection of a specimen in this region. A total of 28 specimens was collected at both domicile and peridomicile, showing a 17.8% infection rate. The main collection site was a woodshed, and despite the collection of adults in the dwelling, we did not find eggs, exuviae, or nymphs. One female monitored from collection day until death laid 566 eggs, with a hatching rate of 95%, showing an increase of oviposition when cohabited with a male. The results showed the capacity that T. pallidipennis has to infest areas (mainly human dwellings) when it settles down, which would imply a risk for the population that lives in the locality.

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We examined the degree of reproductive isolation in four populations of Triatoma mexicana Herrich-Schaeffer from Mexico along with fertility and the segregation of morphological characteristics in two generations of offspring from crosses between these populations. The percentage of couples with (fertile) offspring was high among all sets of crosses between cohorts from Peñamiller, Meztitlán, and Orizabita. It was low in crosses involving a cohort from Tierra Blanca, mainly in crosses with Meztitlán. Among sets of crosses involving Tierra Blanca specimens, whole first-generation (F1) individuals were morphologically similar to the specimens from other locations. All F1 individuals of crosses involving Peñamiller looked like Peñamiller. However, in crosses between F1 and F1 progeny of parental crosses, alleles for size, overall color, length of head, ante and post ocular distance, and humeral angle apparently had Mendelian dominant/recessive relationships. The cohorts from Peñamiller and Meztitlán seemed to be dominant with respect to Orizabita and Tierra Blanca. Results indicated that cohorts from Peñamiller, Meztitlán, and Orizabita were not reproductively isolated. In contrast, Tierra Blanca was reproductively isolated from the other three populations of T. mexicana and is apparently undergoing an early divergence process of speciation for allopatry.

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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.

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Triatomines display most of their activities during the night. Before sunrise, they search, select and occupy adequate shelters to stay during the photophase, avoiding exposure to diurnal predators. In this work, we first explored the interactions between individuals of the same or different species in the shelter selection process of Triatoma infestans (Klug 1834) and Rhodnius prolixus (Stål 1859). When two groups of insects (either of different nutritional status, nymphal instar or species) were released together over an experimental arena containing two identical shelters, all nymphs were distributed randomly, suggesting the absence of intra- and inters-pecific interactions. Secondly, we analysed their preferences for particular features of shelters by releasing one group of insects (either T. infestans or R. prolixus) over an arena containing two different refuges. Nymphs exhibited preferences for darker shelters with a vertical orientation of its substrate and elevated from the ground, highlighting the importance of such features in a shelter selection context. We conclude that these species disregard the presence of other individuals but evaluate certain characteristics of the shelters to choose them. This information may contribute to understanding the colonization/recolonization dynamic processes of these Chagas disease vectors.

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Triatomines are an important group of insects in the Americas. They serve as transmission vectors for Trypanosoma cruzi, the etiologic agent responsible for the deadly Chagas disease in humans. The digenetic parasite has a complex life cycle, alternating between mammalian and insect hosts, facing different environments. In the insect vector, the metacyclic trypomastigote (non-replicative) and epimastigote (replicative) stages face a set of insect-mediated environmental changes, such as intestinal pH, body temperature, nutrient availability, and vector immune response. These insects have the ability to differentiate between self and non-self-particles using their innate immune system. This immune system comprises physical barriers, cellular responses (phagocytosis, nodules and encapsulation), humoral factors, including effector mechanisms (antimicrobial peptides and prophenoloxidase cascade) and the intestinal microbiota. Here, we consolidate and synthesize the available literature to describe the defense mechanisms deployed by the triatomine vector against the parasite, as documented in recent years, the possible mechanisms developed by the parasite to protect against the insect's specific microenvironment and innate immune responses, and future perspectives on the Triatomine-Trypanosome interaction.

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Resumo Introdução A vigilância da doença de Chagas (DC), baseada na participação popular, ocorre por meio da detecção e notificação de insetos suspeitos de serem vetores da DC aos Postos de Informação de Triatomíneos (PITs). Objetivo Compreender as ideias e concepções dos moradores em áreas rurais dos municípios da Microrregião de Saúde de Itaúna (MSI) em relação a aspectos relacionados à DC, seus vetores e serviços de saúde. Método Em 2016, foram realizados quatro grupos focais nos municípios da MSI. Esses grupos focais foram gravados, transcritos e analisados utilizando a técnica de análise de conteúdo. Neste processo, identificamos e categorizamos unidades de análise tanto dentro de cada grupo focal quanto entre eles. Resultados Descobrimos que há compreensão por parte de alguns moradores sobre a natureza da transmissão da DC, as características morfológicas e hábitos dos vetores, o encaminhamento do vetor para os PITs e o diagnóstico da DC. Também encontramos relatos da ausência de intervenções educacionais e de saúde relacionadas à DC. Conclusão Compreender as concepções e ideias sobre a DC das populações em áreas endêmicas é fundamental para desenvolver futuras estratégias envolvendo a participação popular.

Abstract Background The surveillance of Chagas disease (CD) based on public participation is carried out through the detection and notification of insects suspected of being vectors of CD to Triatomine Information Posts (TIPs). Objective To understand the ideas and conceptions of residents in rural areas of the municipalities of the Micro-region of Health de Itaúna (MHI) regarding aspects related to CD, its vectors, and health services. Method In 2016, four focus groups were conducted in the municipalities of MHI. These focus groups were recorded, transcribed, and analyzed using the content analysis technique. In this process, units of analysis, both within each focus group and between them, were identified and categorized. Results It was found that some residents have a good understanding of the nature of CD transmission and of the morphological characteristics and habits of the vectors, in addition to an understanding of the forwarding of the vector to TIPs, and the diagnosis of CD. Reports of the absence of education and health interventions related to CD were also found. Conclusion Understanding the conceptions and ideas about CD of populations in endemic areas is fundamental to developing future strategies involving public participation.

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ABSTRACT Two triatomine genera (Panstrongylus and Triatoma) have essentially been recorded in Rio Grande do Sul State, Brazil. Panstrongylus megistus should be highlighted since this species is one of the main vectors of Trypanosoma cruzi in Brazil, due to its wide geographical distribution and the high susceptibility to this protozoan. This study aimed to present not only the occurrence and distribution of P. megistus in the Porto Alegre city's metropolitan area (PAMA), Rio Grande do Sul State, Brazil, but also the rates of T. cruzi infection, from 2009 to 2020. The PAMA, which comprises 34 cities and 4.4 million habitants, extends across the transition area in two biomes - Pampa and Mata Atlantica - found in the state. Results showed that P. megistus was recorded in 76.5% of cities (i.e., 26 out of 34), mainly in Porto Alegre city, where the vector was found in 11 out of the 12 years that were monitored. Three hundred and nineteen specimens were captured. Two hundred and sixty-seven specimens (83.7%) were located intradomicile (p < 0.0001), while 52.3% positivity for T. cruzi was found. Thus, P. megistus is important in the PAMA, because it invades and colonizes the households. Moreover, the high rates of T. cruzi infection have drawn attention.