The risk of vector transmission of Trypanosoma cruzi remains high in the State of Paraná.

BACKGROUND: Monitoring and analysing the infection rates of the vector of Trypanosoma cruzi, that causes Chagas disease, helps assess the risk of transmission. OBJECTIVES: A study was carried out on triatomine in the State of Paraná, Brazil, between 2012 and 2021 and a comparison was made with a previous study. This was done to assess the risk of disease transmission. METHODS: Ecological niche models based on climate and landscape variables were developed to predict habitat suitability for the vectors as a proxy for risk of occurrence. FINDINGS: A total of 1,750 specimens of triatomines were recorded, of which six species were identified. The overall infection rate was 22.7%. The areas with the highest risk transmission of T. cruzi are consistent with previous predictions in municipalities. New data shows that climate models are more accurate than landscape models. This is likely because climate suitability was higher in the previous period. MAIN CONCLUSION: Regardless of uneven sampling and potential biases, risk remains high due to the wide presence of infected vectors and high environmental suitability for vector species throughout the state and, therefore, improvements in public policies aimed at wide dissemination of knowledge about the disease are recommended to ensure the State remains free of Chagas disease.

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

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

Insecticidal activity of fluralaner (Exzolt®) administered to Gallus gallus domesticus against triatomines (Hemiptera, Reduviidae, Triatominae).

BACKGROUND: Triatoma infestans, Triatoma brasiliensis, Triatoma pseudomaculata and Rhodnius prolixus are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Chickens serve as an important blood food source for triatomines. This study aimed to assess the insecticidal activity of fluralaner (Exzolt®) administered to chickens against triatomines (R. prolixus, T. infestans, T. brasiliensis and T. pseudomaculata). METHODS: Twelve non-breed chickens (Gallus gallus domesticus) were randomized based on weight into three groups: negative control (n = 4); a single dose of 0.5 mg/kg fluralaner (Exzolt®) (n = 4); two doses of 0.5 mg/kg fluralaner (Exzolt®) (n = 4). Nymphs of 3rd, 4th and 5th instars of R. prolixus, T. infestans, T. brasiliensis and T. pseudomaculata (all n = 10) were allowed to feed on chickens before treatment, and at intervals of 1, 7, 14, 21, 28, 35 and 56 days after treatment, with insect mortality determined. RESULTS: Treatment with two doses of fluralaner showed higher insecticidal efficacy against R. prolixus, T. infestans and T. brasiliensis compared to the single-dose treatment. Similar insecticidal efficacy was observed for T. pseudomaculata for one and two doses of fluralaner. Insecticidal activity of fluralaner (Exzolt®) against triatomine bugs was noted up to 21 and 28 days after treatment with one and two doses of fluralaner, respectively. CONCLUSIONS: The results demonstrate that treatment of chickens with fluralaner (Exzolt®) induces insecticidal activity against triatomines for up to 28 days post-treatment, suggesting its potential use as a control strategy for Chagas disease in endemic areas.

Cartaz para estímulo ao envio de insetos suspeitos de serem triatomíneos (barbeiros)

A vigilância entomológica para os vetores secundários da doença de Chagas é atualmente descentralizada aos municípios. A complexidade da paisagem urbana da cidade de São Paulo e a baixa densidade de insetos invasores de domicílios, sugere ser imprescindível a participação popular na captura e envio de insetos suspeitos como método mais sensível de vigilância. Os triatomíneos recebidos pelo LABFAUNA são identificados quanto à espécie e submetidos a pesquisa de Trypanosoma cruzi no conteúdo digestivo. Todo triatomíneo notificado gera uma vistoria no respectivo local de procedência do inseto, com objetivo de detectar e eliminar colônias domiciliadas.

Transmission ecology of Trypanosoma cruzi by Rhodnius prolixus (Reduviidae: Triatominae) infesting palm-tree species in the Colombian Orinoco, indicates risks to human populations.

BACKGROUND: Chagas disease, affecting approximately eight million individuals in tropical regions, is primarily transmitted by vectors. Rhodnius prolixus, a triatomine vector, commonly inhabits in ecotopes with diverse palm tree species, creating optimal conditions for vector proliferation. This study aims to explore the transmission ecology of Trypanosoma cruzi, the causative parasite of Chagas disease, by investigating the feeding patterns and natural infection rates of R. prolixus specimens collected from various wild palm species in the Colombian Orinoco region. MATERIALS AND METHODS: To achieve this objective, we sampled 35 individuals from three palm species (Attalea butyracea, Acrocomia aculeata, and Mauritia flexuosa) in a riparian forest in the Casanare department of eastern Colombia, totaling 105 sampled palm trees. DNA was extracted and analyzed from 115 R. prolixus specimens at different developmental stages using quantitative PCR (qPCR) for T. cruzi detection and identification of discrete typing units. Feeding preferences were determined by sequencing the 12S rRNA gene amplicon through next-generation sequencing. RESULTS: A total of 676 R. prolixus specimens were collected from the sampled palms. The study revealed variation in population densities and developmental stages of R. prolixus among palm tree species, with higher densities observed in A. butyracea and lower densities in M. flexuosa. TcI was the exclusive T. cruzi discrete typing unit (DTU) found, with infection frequency positively correlated with R. prolixus abundance. Insects captured in A. butyracea exhibited higher abundance and infection rates than those from other palm species. The feeding sources comprised 13 mammal species, showing no significant differences between palm species in terms of blood sources. However, Didelphis marsupialis and Homo sapiens were present in all examined R. prolixus, and Dasypus novemcinctus was found in 89.47% of the insects. CONCLUSION: This study highlights the significance of wild palms, particularly A. butyracea, as a substantial risk factor for T. cruzi transmission to humans in these environments. High population densities and infection rates of R. prolixus were observed in each examined palm tree species.

Thinking green: Insecticidal effect of biorational solutions against Triatoma pallidipennis Stal (Hemiptera: Triatominae).

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.

Série educativa da fauna sinantrópica: barbeiro (panstrongylus megistus)

Folheto educativo referente ao barbeiro: biologia, medidas preventivas, importância para a saúde e doença de chagas

Trapping Triatominae Bugs Using Mice-Baited Traps along the Peninsula of Baja California, Mexico.

During an exploratory fieldtrip along the peninsula of Baja California, Mexico, we used mice-baited traps in search of Triatominae, the vectors of Chagas disease. A total of 433 traps were set in five localities following a latitude gradient along the peninsula. Triatominae were caught in rocky ecotopes in two localities. The specimens were identified as Paratriatoma hirsuta in the first locality, and Dipetalogaster maxima in the second, in accordance with the reported distributions of these species. The overall trap success was 3.1%, with an average of 1.3 bugs per positive trap. In the site with most bugs collected, trap success was 26.8%. To the best of our knowledge, this is the first time that mice-baited traps have been used in this geographic area to collect Triatominae bugs. This short report confirms the usefulness of this trapping system when standardized protocols are needed.

Analysis of the maternal inheritance hypothesis of the exochorium in eggs from hybrids of Chagas disease vectors.

Morphological studies applied to the taxonomy of the Triatominae cover various structures (head, wing, thorax, genitalia, and eggs). Exochorial structures of hybrid eggs were characterized and compared with the parents, demonstrating that hybrids presented characteristics identical to the exochorial pattern observed in the females of the crosses, which resulted in the hypothesis that the pattern of triatomine eggs is possibly a characteristic inherited from females. Thus, we characterized the exochorium of the eggs of several triatomine hybrids and compared them with the parents, to assess the pattern of segregation and test the hypothesis of maternal inheritance. Hybrids were obtained in at least one direction from all crosses. The analysis of the exochorium of the eggs of the hybrids showed different patterns of segregation: "exclusively paternal", "predominantly maternal", "predominantly paternal", "mutual", and "differential". Curiously, none of the hybrids evaluated presented characteristics that segregated exclusively from the female parental species. Thus, we demonstrate that the hypothesis of maternal inheritance of the exochorium pattern of eggs is not valid and we emphasize the importance of alternative/combined tools (such as integrative taxonomy) for the correct identification of these insect vectors (mainly in view of possible natural hybridization events due to climate and environmental changes).

Trypanosoma cruzi infection reduces the population fitness of Mepraia spinolai, a Chagas disease vector.

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.

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.

What is behind the success of terrestrial bromeliads as microhabitat for the sylvatic triatomine Mepraia spinolai?

Puya alpestris, P. berteroniana and P. chilensis (Bromeliaceae) are terrestrial plants present in north-central Chile, considered important part of the shrub flora due to their abundance and close interaction with animals. A previous study showed that bromeliad cover positively correlates with the abundance of the sylvatic triatomine vector Mepraia spinolai, only when infected by the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. Here, we assessed the biological interactions and abiotic conditions provided by these Puya species to M. spinolai. During the austral summers of 2015 and 2016, we sampled 17 sites with presence of M. spinolai colonies. In each site, we estimated the presence of bromeliad and its cover proportion, and placed a camera trap for three months near a M. spinolai colony to record the vertebrates potentially interacting with this triatomine. Three of the camera traps were placed right in front of M. spinolai-colonized bromeliads. At the same time, triatomines present under these bromeliads were collected to assess their blood meal by Next Generation Sequencing. Between July 2017 and January 2018, we examined the abiotic conditions (temperature and humidity) under bromeliad, under rocks and at ground level. We detected 40 vertebrate species associated to Puya spp. (18 birds, 16 mammals, and 6 reptiles). Puya spp. are a resource for keystone species in T. cruzi sylvatic transmission, including small mammals (Octodon degus, Phyllotis darwini) and lizard species (Liolaemus spp.), detecting a positive association between bromeliad presence and availability of reptiles and non-domestic mammals. Native rodents and humans were the most represented vertebrates in the diet of M. spinolai collected under bromeliads. Temperatures were more stable under bromeliad, showing lower amplitude (up to 14.3 °C) compared to under rocks (23.7 °C) or at ground level (49.6 °C). Bromeliads present in the semiarid-Mediterranean ecosystem provide feeding opportunities for triatomines, and act as buffer of abiotic conditions reducing daily thermal amplitude. The presence of bromeliads near human settlements should be carefully monitored, especially because their leaves are consumed by people and browsed by livestock present in endemic areas of Chagas disease.

Revised New World bioregions and environmental correlates for vectors of Chagas disease (Hemiptera, Triatominae).

The subfamily Triatominae includes a group of hematophagous insects, vectors of the parasite Trypanosoma cruzi, which is the etiological agent of Chagas disease, also known as American trypanosomiasis. Triatomines occur in the Old and New World and occupy diverse habitats including tropical and temperate areas. Some studies suggest the distributions of triatomines group into three or four regions. This study objectively determined bioregions focused specifically on New World Triatominae, using clustering and ordination analysis. We also identified indicator species by bioregion and investigated relationships among bioregions and environmental variables using redundancy analysis and multivariate regression trees. We delineated seven bioregions specific to Triatominae and linked each with indicator species. This result suggests more biogeographical structure exists than was revealed in earlier studies that were more general, subjective, and based on older taxonomic and distributional information. Precipitation, elevation, and vegetation were important variables in the delimitating bioregions. This implies that more detailed study of how these factors influence triatomine distributions could benefit understanding of how Chagas disease is spread.

First evidence of gonadal hybrid dysgenesis in Chagas disease vectors (Hemiptera, Triatominae): gonad atrophy prevents events of interspecific gene flow and introgression.

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).

Acute Chagas Disease Presenting as Preseptal Cellulitis.

Chagas disease, also known as American trypanosomiasis, is caused by Trypanosoma cruzi, a parasite transmitted by hematophagous triatomine insects (subfamily Triatominae) belonging to the Reduviidae family, order Hemiptera. Infection occurs through contact with the feces of the infected vector at the site of its bite or on intact mucosa. [Pediatr Ann. 2023;52(10):e394-e397.].

Triatominae (Hemiptera: Reduviidae) fauna in bird nests: the case of Morrinhos, Ceará, Brazil.

Triatominae are associated with various Brazilian habitats, including bird nests, animal burrows, and peridomestic structures. Despite extensive studies on triatomines in domiciliary environments in Ceará, Brazil, there has been limited research on their presence in the wild. This study focuses on the municipality of Morrinhos in Ceará, which is characterized by a Caatinga biome and riparian forests along the Acaraú River. During the study, a total of 185 nests of Pseudoseisura cristata were analyzed in rural locations and triatomines were collected in 26 nests from 12 different locations. A total of 117 triatomines was collected, belonging to three species: Psammolestes tertius, Rhodnius nasutus, and Triatoma pseudomaculata. Rhodnius nasutus was the only species found in a nest inhabited by Didelphis albiventris. Nests of P. cristata serve as shelters for various animals, providing an ideal environment for triatomines to establish colonies due to their proximity to food sources and their generalist feeding habits. The incorporation of anthropogenic materials by birds in nest construction can indirectly affect the presence of other animals that may serve as food sources for triatomines. Understanding the interactions between triatomines, birds, and their habitats is essential for assessing the risks associated with triatomine infestation in wild ecosystems.

Diet of the sylvatic triatomine Mepraia spinolai: Association with Trypanosoma cruzi infection near human settlements.

The proximity between infectious disease vector populations and human settlements, and the infection prevalence of vector populations can determine the rate of encounters between vectors and humans and hence infection risk. The diet of sylvatic triatomine vectors (kissing bugs) provides evidence about the host species involved in the maintenance of the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. Here, we characterized the diet of the Chilean endemic triatomine Mepraia spinolai using Next Generation Sequencing (NGS), and evaluated the relation between T. cruzi infection status and proximity to human settlements, with the proportion of human and human-associated (domestic and synanthropic) vertebrates in the diet. We sampled 28 M. spinolai populations, covering a latitudinal range of ∼800 km in Chile. For each population, genomic DNA was obtained from M. spinolai intestinal content. We assessed T. cruzi infection individually, and sequenced vertebrate cytochrome b to characterize the diet from infected and uninfected pooled samples. Human and human-associated animals were present in the diet of both T. cruzi-infected (13.50 %) and uninfected (10.43 %) kissing bugs. The proportion of human and human-associated vertebrates in the diet of infected M. spinolai was negatively associated with the distance from surrounding human settlements, but no relationship was detected for uninfected kissing bugs. This pattern could be related to alterations of kissing bug feeding behavior when infected by the protozoan. Our results highlight the relevance of developing a deeper knowledge of the wild transmission cycle of T. cruzi, thus advancing in the surveillance of vectors present in the natural environment near human settlements.

First Report of Eratyrus cuspidatus (Hemiptera: Reduviidae) Infected with Trypanosoma cruzi in Peridomestic Environment in Chiapas, Mexico.

Background: Triatomine bugs are natural vectors of Trypanosoma cruzi, which causes Chagas disease or American trypanosomiasis. The role of sylvatic triatomine species as vectors of T. cruzi in Mexico remains to be fully understood. Our research on the epidemiology of Chagas disease in Southeastern Mexico involved sampling triatomines in rural settings. Materials and Methods: A triatomine was collected in a peridomestic environment of a rural dwelling in the state of Chiapas. The triatomine was identified morphologically as an adult female Eratyrus cuspidatus Stal. Results: Microscopic analysis revealed flagellate forms of T. cruzi in the feces of the E. cuspidatus collected. This was confirmed by quantitative polymerase chain reaction. Amplification of the mini-exon gene showed that the T. cruzi infecting E. cuspidatus corresponded to lineage I. Conclusions: This is the first report from Mexico of E. cuspidatus found infected in a human dwelling, which represents an important adaptation process to inhabit human environments.

Insights into the microRNA landscape of Rhodnius prolixus, a vector of Chagas disease.

The growing interest in microRNAs (miRNAs) over recent years has led to their characterization in numerous organisms. However, there is currently a lack of data available on miRNAs from triatomine bugs (Reduviidae: Triatominae), which are the vectors of the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. A comprehensive understanding of the molecular biology of vectors provides new insights into insect-host interactions and insect control approaches, which are key methods to prevent disease incidence in endemic areas. In this work, we describe the miRNome profiles from gut, hemolymph, and salivary gland tissues of the Rhodnius prolixus triatomine. Small RNA sequencing data revealed abundant expression of miRNAs, along with tRNA- and rRNA-derived fragments. Fifty-two mature miRNAs, previously reported in Ecdysozoa, were identified, including 39 ubiquitously expressed in the three tissues. Additionally, 112, 73, and 78 novel miRNAs were predicted in the gut, hemolymph, and salivary glands, respectively. In silico prediction showed that the top eight most highly expressed miRNAs from salivary glands potentially target human blood-expressed genes, suggesting that R. prolixus may modulate the host's gene expression at the bite site. This study provides the first characterization of miRNAs in a Triatominae species, shedding light on the role of these crucial regulatory molecules.