Triatomine Infestation Research Articles

Slow recovery rates and spatial aggregation of Triatoma infestans populations in an area with high pyrethroid resistance in the Argentine Chaco

BackgroundThe emergence of pyrethroid resistance has threatened the elimination of Triatoma infestans from the Gran Chaco ecoregion. We investigated the status and spatial distribution of house infestation with T. infestans and its main determinants in Castelli, a municipality of the Argentine Chaco with record levels of triatomine pyrethroid resistance, persistent infestation over 2005–2014, and limited or no control actions over 2015–2020.MethodsWe conducted a 2-year longitudinal survey to assess triatomine infestation by timed manual searches in a well-defined rural section of Castelli including 14 villages and 234 inhabited houses in 2018 (baseline) and 2020, collected housing and sociodemographic data by on-site inspection and a tailored questionnaire, and synthetized these data into three indices generated by multiple correspondence analysis.ResultsThe overall prevalence of house infestation in 2018 (33.8%) and 2020 (31.6%) virtually matched the historical estimates for the period 2005–2014 (33.7%) under recurrent pyrethroid sprays. While mean peridomestic infestation remained the same (26.4–26.7%) between 2018 and 2020, domestic infestation slightly decreased from 12.2 to 8.3%. Key triatomine habitats were storerooms, domiciles, kitchens, and structures occupied by chickens. Local spatial analysis showed significant aggregation of infestation and bug abundance in five villages, four of which had very high pyrethroid resistance approximately over 2010–2013, suggesting persistent infestations over space-time. House bug abundance within the hotspots consistently exceeded the estimates recorded in other villages. Multiple regression analysis revealed that the presence and relative abundance of T. infestans in domiciles were strongly and negatively associated with indices for household preventive practices (pesticide use) and housing quality. Questionnaire-derived information showed extensive use of pyrethroids associated with livestock raising and concomitant spillover treatment of dogs and (peri) domestic premises.ConclusionsTriatoma infestans populations in an area with high pyrethroid resistance showed slow recovery and propagation rates despite limited or marginal control actions over a 5-year period. Consistent with these patterns, independent experiments confirmed the lower fitness of pyrethroid-resistant triatomines in Castelli compared with susceptible conspecifics. Targeting hotspots and pyrethroid-resistant foci with appropriate house modification measures and judicious application of alternative insecticides with adequate toxicity profiles are needed to suppress resistant triatomine populations and prevent their eventual regional spread.Graphical

Entomological investigation of triatomine fauna in rural communities in the state of Piauí, Brazilian semi-arid region

Objective: To describe the characteristics and distribution of triatomine fauna in rural communities of Simplício Mendes municipality, located in the state of Piauí, Brazilian semiarid region. Methods: This is a cross-sectional study and entomological survey conducted from 2022 to 2023. Insects were captured using active search method in all human dwellings, which were georeferenced, followed by characterized of species, sex, developmental stage, and identification of presence of infection by trypanosomatids. Results: All households (n=178) in 10 rural localities of the municipality were investigated, resulting in a household triatomine infestation rate of 14%. A total of 268 insects were collected, predominantly species from the Triatoma brasiliensis complex (n=190), immature developmental stage (n=172), and originating from peridomestic environments (n=250). The rate of triatomines with natural infection by Trypanosoma cruzi was 1.1%. Conclusion: The finding of infestation by species from the T. brasiliensis complex with higher concentration cohabiting extradomestic spaces, wide dispersion, and presence of natural infection by T. cruzi signals conditions for the maintenance of vector-borne transmission of Chagas disease in the municipality.

Irrigation, migration and infestation: a case study of Chagas disease vectors and bed bugs in El Pedregal, Peru.

The city of El Pedregal grew out of a desert, following an agricultural irrigation project in southern Peru. To describe infestation patterns by triatomines and bed bugs and their relationship to migration and urbanization. We conducted door-to-door entomological surveys for triatomines and bed bugs. We assessed spatial clustering of infestations and compared the year of construction of infested to un-infested households. To gain a better understanding of the context surrounding triatomine infestations, we conducted in-depth interviews with residents to explore their migration histories, including previous experiences with infestation. We inspected 5,164 households for Triatoma infestans (known locally as the Chirimacha); 21 (0.41%) were infested. These were extremely spatially clustered (Ripley's K p-value < 0.001 at various spatial scales). Infested houses were older than controls (Wilcoxon rank-sum: W = 33; p = 0.02). We conducted bed bug specific inspections in 34 households; 23 of these were infested. These were spatially dispersed across El Pedregal, and no difference was observed in construction age between bed bug infested houses and control houses (W = 6.5, p = 0.07). The establishment of agribusiness companies in a desert area demanded a permanent work force, leading to the emergence of a new city. Migrant farmers, seeking work opportunities or escaping from adverse climatic events, arrived with few resources, and constructed their houses with precarious materials. T. infestans, a Chagas disease vector, was introduced to the city and colonized houses, but its dispersal was constrained by presence of vacant houses. We discuss how changes in the socioeconomic and agricultural landscape can increase vulnerability to vector-borne illnesses.

Perceptions of Problems with Household Insects: Qualitative and Quantitative Findings from Peri-Urban Communities in Arequipa, Peru.

Vector-borne diseases continue to impose a major health burden on Peru and neighboring countries. The challenge of addressing vector-borne disease is compounded by changing social, economic, and climatic conditions. Peri-urban Arequipa is an important region to study insect infestations because of ongoing challenges with disease vectors such as triatomines and a variety of other insects. We conducted surveys (N = 1,182) and seven focus groups (average seven participants) in peri-urban Arequipa to explore knowledge of and perception toward various insects that infest the region. Focus group participants reported the presence of a wide variety of insects in and around the home, including disease vectors such as triatomines (also identified by 27.2% of survey households), mosquitoes, spiders, and bed bugs, as well as nuisance insects. Health concerns related to insects included vector-borne diseases, spider bites, allergies, and sequelae from bed bug bites, and hygiene concerns. A majority of participants in the quantitative surveys identified triatomines as the insect they were most worried about (69.9%) and could identify Chagas disease as a health risk associated with triatomines (54.9%). Insect infestations in peri-urban Arequipa present multiple burdens to residents, including injury and illness from triatomines and other insects, as well as potential mental and economic concerns related to insects such as bed bugs. Future initiatives should continue to address triatomine infestations through educational outreach and implement a more holistic approach to address the burden of both disease and nuisance insects.

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.

A qualitative exploration of knowledge of Chagas disease among adolescents in rural Ecuador.

Chagas disease (CD) is a neglected tropical disease that affects 6 to 7 million people worldwide. In South America, CD is a major health problem in several regions, causing more than 12 000 deaths per year. CD is caused by a parasite called Trypanosoma cruzi, mostly transmitted through the contaminated feces of certain species of triatomine bug, commonly known as the 'kissing bug'. CD is endemic in Loja province in the southern region of Ecuador, where triatomines have been found in 68% of communities. Previous promotion of healthy practices in Loja province have included educational programs directed toward youth to affirm cultural and social norms that support health and prevent CD transmission. The present study was designed to evaluate current knowledge related to CD among youth in the three communities of Loja province following previous intervention programs. A descriptive, qualitative approach was applied using individual semi-structured interviews with 14 young people (eight females, six males) from three rural communities in Loja province. Interviews assessed knowledge about CD transmission, knowledge about the parasite-vector-disease pathway, and the role of youth in preventing Chagas disease in their communities. Following a thematic analysis of the data, the study results showed there is cursory knowledge of the triatomine insect that can carry the causative parasite for CD. Participants were able to generally talk about the vector, habitat and prevention practices for triatomine infestation. Nevertheless, limited understanding of transmission dynamics in the parasite-vector-disease pathway itself was found. One major finding was that prevention practices were not correctly applied or followed, increasing the risk of exposure in the community. Youth also articulated that CD is stigmatized in their communities, which may be a barrier for prevention efforts. Gaps in knowledge about the parasite-vector-disease pathway were identified among youth. Overall, youth responses indicated positive regard for prevention practices and a desire to be involved in prevention programs. Developing educational programs focusing on CD transmission may be needed to improve control and prevention of this parasitic disease. The implications of these findings are discussed for developing effective control programs in the region.

Laboratory Evaluation and Field Feasibility of Micro-Encapsulated Insecticide Effect on Rhodnius prolixus and Triatoma dimidiata Mortality in Rural Households in Boyacá, Colombia.

Chagas disease is a neglected vector-borne zoonosis caused by the parasite Trypanosoma cruzi that is primarily transmitted by insects of the subfamily Triatominae. Although control efforts targeting domestic infestations of Rhodnius prolixus have been largely successful, with several regions in Boyacá department certified free of T. cruzi transmission by intradomicile R. prolixus, novel native species are emerging, increasing the risk of disease. Triatoma dimidiata is the second most important species in Colombia, and conventional control methods seem to be less effective. In this study we evaluated the efficacy and usefulness of micro-encapsulated insecticide paints in laboratory conditions and its applicability in rural communities to avoid triatomine domiciliation. Laboratory conditions measured mortality at 6 months and 12 months, with an average mortality between 93-100% for T. dimidiata and 100% for R. prolixus. Evaluation of triatomine infestation in rural households was measured after one year, with an overall perception of effectiveness in reducing household domiciliation. Although triatomines were still spotted inside and around the homes, our findings demonstrate the ability of micro-encapsulated insecticide to prevent colonization inside the households when comparing infestation rates from previous years. Current control measures suggest insecticide spraying every six months, which implies great economic cost and logistical effort. Complementary triatomine control measures with insecticide spraying and micro-encapsulated insecticide paint would make public health efforts more efficient and reduce the frequency of treatment.

Risk factors and spatial analysis for domiciliary infestation with the Chagas disease vectorTriatoma venosain Colombia

Background:In Colombia, communities living in the Andean region are the most affected by Chagas disease due to the presence of the main vectors, the environmental and risk factors associated with house infestation. Triatoma venosa is classified as a secondary vector that is frequently found in the departments of Boyaca and Cundinamarca, but epidemiological information and its association with risk factors in domestic and peridomestic areas is unknown. The study aimed to evaluate housing and environmental characteristics associated with domestic and peridomestic infestation by T. venosa and a risk map was estimated.Methods:A cross-sectional study was conducted in municipalities of Boyaca and Cundinamarca, Colombia. From March to July 2015, triatomine infestation screening surveys were conducted in 155 households. Multivariate analysis was performed to evaluate associations with the infestation and ecological niche modeling was estimated using environmental variables.Results:No statistical association was found with any of the housing variables in the adjusted multivariate analysis. However, in raw relationship infestation was associated with bushes < 10 m (OR = 3; 95% CI: 1.3–7.3) and higher temperature p value < 0.05. The developed final risk map pointed to 12 municipalities with no previous report of the disease, which should be sampled for the presence of T. venosa.Conclusion:This study highlights the relationship between environmental factors and T. venosa in Colombia and the importance of modeling tools to improve mapping efforts. Additional studies are needed to verify the association with bushes and higher temperatures and to verify infestation in predicted risk area with no previous report of the species

Seroprevalence of Chagas disease in Southern Brazilian cardiac patients and their knowledge about the parasitosis and vectors.

Chagas disease (CD) is considered a typical low-income population sickness of the developing countries in Latin America. Given the historical relevance of CD in individuals in southern Rio Grande do Sul (RS) State, Brazil, the aim of this study was to identify the knowledge of the CD and its vectors by cardiac patients, and the prevalence of anti-T cruzi antibodies in these individuals in Pelotas, city located in Rio Grande do Sul (RS) state, Brazil. The subjects with cardiac disease were submitted to a semi-structured questionnaire as well as two serological tests in order to detect anti-T. cruzi IgG antibodies. Of the individuals that born in municipalities showing the highest triatomine infestation rates in recent decades, 81.8% were able to recognize the vector insect (p = 0.0042; OR = 5.9), and 83.3% reported either themselves or someone in their families to have CD (p = 0.043, OR = 5.2). Of the 54 patients submitted to serological analysis, only 01 patient (1.9%) was positive for anti-T. cruzi antibodies, a 55 year old man from the rural area of Canguçu county. This study provides support for the evaluation to be extended to other cardiology centers, given the importance of Chagas disease in Brazil.

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.

Domiciliation and sympatry of Triatoma maculata and Rhodnius prolixus, risk of Trypanosoma cruzi transmission in villages of Anzoátegui, Venezuela.

The domiciliation of Triatoma maculata and Rhodnius prolixus and the entomological risk indicators for the transmission of Trypanosoma cruzi, an etiological agent of Chagas Disease-CD, were studied in rural villages of Anzoátegui state, Venezuela. Nightly home visits were made for 4months/year, for 2years, to search for and capture triatomines in human settlements. For six of the evaluated villages, 16.4% (11/67) of houses were found with triatomine infestation; obtaining 151 triatomines in all their ontogenetic stages, of which 54.3% (82/151) corresponded to T. maculata and 45.7% (69/151) to R. prolixus. In 7.5% of the evaluated houses, both species were presented in sympatry. Entomological indicators of transmission risk were higher for T. maculata in relation to R. prolixus. Inoculation of fecal flagellates of triatomines produced 2.92 × 105 flagellates/mL of blood in mean and 100% mortality in the murine model. Molecular tests (satellite DNA, kDNA and DTUs studies) demonstrated the presence of T. cruzi, all compatible with TcI. The food source determined by IESPA, revealed that R. prolixus showed less eclecticism in relation to T. maculata in the use of blood sources. This could be an indicator of an older domiciliation with low dispersion between ecotopes. The sympatry of T. maculata and R. prolixus had been recorded in natural niches, but for the first time it is recorded inside the houses in rural villages of the Anzoátegui state. Human dwellings can constitute an adequate niche, with available food sources for both triatomines species and with the risk of establishing AT/CD as zoonosis or zooanthroponosis.

Rhodnius spp. infestation in palm trees and natural infection by Trypanosoma cruzi and Trypanosoma rangeli in periurban and rural areas of state of the Rondônia, in the Brazilian Amazon

The state of Rondônia in the Brazilian Amazon is prone to diseases transmitted by insect vectors because of the environmental and population changes resulting from large hydroelectric projects and the expansion of agricultural and livestock industries. The first case of Chagas disease by vectorial transmission was recorded in 2019 in a rural area in Rondônia, reinforcing the need for entomological surveillance. Hence, our goal was to estimate the abundance of Rhodnius spp. in palm trees located in rural and periurban areas and in Brazil-Bolivia border regions, perform domiciliary searches, and check for possible associations between triatomines and the presence/absence of palm-inhabiting fauna and outdoor farming, domestic animals, and buildings. The sampling took place in five municipalities of Rondônia in 2014 (June to August) and 2015 (April to June). Triatomines were collected by active searches during the selective pruning of palm tree crowns. Domiciliary inspections lasted from 30 to 60 min. A set of captured triatomines was analyzed for Trypanosoma cruzi and T. rangeli infection by PCR. Overall, 496 insects were captured during sampling of 150 palms in rural areas and 150 in periurban areas. No triatomine was found during active searches of 59 dwelling either indoors or outdoors. The majority of triatomines caught in the palm trees were identified as Rhodnius robustus (98.6%), and seven specimens were R. pictipes. Triatomine infestation was observed in only 20% of the sampled palms (61/300) in the vicinity of 26/59 households. Nearly half of the infested palm trees had only one or two triatomines, and few palms presented more than 15 triatomines. The municipality of Buritis had the highest triatomine abundance and percentage of infested palms; however, the highest triatomine density per infested palm was observed in Alvorada D'Oeste, where a quarter of the palms were infested. Ants, arachnids, termites, reptiles, and rodents were frequently found in palm trees. Dogs were the predominant domestic animals in households, whereas hens and cattle were the main farming animals. Model estimates showed that the number of triatomines was affected by the presence of henhouses and varied strongly between localities. No relationships were detected between the average number of triatomines and palm fauna and/or palm height. Overall, approximately half of the triatomines were infected with T. cruzi (51.4%) and/or T. rangeli (47.2%), reinforcing the need for continuous entomological surveillance and implementation of community-based approaches because the Brazilian state of Rondônia borders areas experiencing reinfestation by domiciled species and potential colonization of animal shelters by triatomines.

Analysis and solutions of generalized Chagas vectors re-infestation model of fractional order type

• A generalized Chagas vectors re-infestation model of fractional order type is proposed. • Our model considers insecticide treatment as continuous spraying where the spraying rate depends on the rate of detection of infestation and time lag between detection and application of insecticide. • Existence and uniqueness results of solutions are proven. • We prove local and global stability of the proposed model and obtain conditions for unique endemic equilibrium. • The effects of the fractional order and key parameters on the proposed model are examined from the numerical analysis results. • Based on the results obtained, we provide some recommendations useful to better understand and reduce the re-infestation of Chagas disease. Trypanosoma cruzi is the parasite that causes Chagas disease in which Triatomine bugs, a type of reduviid bug, are the carrier. Insecticide spraying is one of the most common measures to reduce triatomine infestation. In this paper, we propose a generalized Chagas vectors re-infestation model of fractional order type. This fractional model has been developed to study insecticide-based strategies for controlling vectors of Chagas disease. Our model considers insecticide treatment as continuous spraying where the spraying rate depends on the rate of detection of infestation and time lag between detection and application of insecticide. We incorporate two spraying rates, r (triatomines detection and only infected housing units are treated with deltamethrin insecticide) and r o (other insects detection and treatment is applied to all units). Existence and uniqueness results of solutions are proven. We prove local and global stability of the proposed model and obtain conditions for unique endemic equilibrium. Our numerical results exposed the intrinsic properties of the model using fractional derivative . Based on our results, triatomines infestation cannot be eradicated when there is migration from the sylvatic areas, control strategies aimed at reducing infestation from the sylvatic areas are highly recommended.

Risk factors for triatominae infestation in a municipality of Colombia.

Background:Identifying risk factors for Triatominae infestation is essential for the development of vector control interventions.Methods:To determine the intra- and peridomiciliary risk factors associated with triatomine infestation, a cross-sectional analytical study was carried out with random cluster sampling in two stages, which included the identification of risk factors by survey and direct observation, as well as the search and capture of triatomines. The detection of trypanosomes in triatomines was carried out by observing the rectal content and then by conventional polymerase chain reaction (PCR).Results:In 21 of the 207 houses inspected, 13 specimens of R. colombiensis and 19 specimens of P. geniculatus were found. Entomological indices included: dispersion 36%, infestation 10%, infection 65%, colonization 4.7%, density 15%, and concentration 152%. An association was found between the presence of Triatominae and the existence of branches and fissures in the floors, as well as with the presence of accumulated objects and with knowledge about Chagas disease. The risk of having triatomines in urban homes is 5.7 times higher than the risk in rural areas [confidence interval (CI) 0.508–67.567]; 6.6 times in houses with cracked soil (CI 0.555–81.994), 6 times in houses located near caneys (CI 0.820–44.781), and 6.16 times with accumulated objects (CI 1.542–39.238).Conclusion:Chagas disease is a complex problem that requires control based on the vector’s elimination or surveillance, which implies identifying species and their distribution, generating alerts, knowledge, and awareness in the population. It is necessary to intensify surveillance activities for the event, especially in changing aspects of Chagas diseases’ transmission dynamics, such as urbanization and the type of housing associated with the vector’s presence.

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.

Determinants of intentions to prevent triatomine infestation based on the health belief model: An application in rural southern Ecuador.

IntroductionControl of triatomine infestation is a key strategy for the prevention of Chagas disease (CD). To promote this strategy, it is important to know which antecedents to behavioral change are the best to emphasize when promoting prevention.ObjectiveThe aim of this study was to determine predictors for intention to prevent home infestation based on the Health Belief Model (HBM), a commonly used health intervention planning theory.Materials & methodsA cross-sectional study was conducted with 112 heads of household in six communities with endemic and high rates of triatomine infestation in Loja province, Ecuador. The data was collected by a questionnaire including perceived severity, susceptibility, benefits to action, barriers to action, and self-efficacy. These data were also used to predict actual infestation of homes.ResultsCommunity members reported strong intentions to prevent home infestation. HBM constructs predicted about 14% of the observed variance in intentions. Perceived susceptibility and severity did not predict behavioral intention well; perceived barriers to small-scale action that reduce likelihood of infestation and self-efficacy in participating in surveillance systems did. Self-efficacy and perception of barriers were equally powerful predictors. The HBM constructs, however, did not predict well actual infestation.ConclusionThe findings supported the HBM as a way to predict intentions to prevent infestation of the home by triatomine bugs. The findings highlight that messages emphasizing self-efficacy in participating in surveillance systems and overcoming barriers to small-scale action that reduce likelihood of infestation, rather than a focus on risk, should be central messages when designing and implementing educational interventions for CD. The gap between behavioral intention and actual infestation reveals the need to assess home practices and their actual efficacy to fully enact and apply the HBM.

Improved detection of house infestations with triatomines using sticky traps: a paired-comparison trial in the Argentine Chaco

BackgroundWe conducted a matched-pairs trial of three methods for detecting house infestation with triatominae bugs in a well-defined endemic rural area in the Argentine Chaco.MethodsThe three methods included a simple double-sided adhesive tape (ST) installed near host resting sites; timed-manual collections with a dislodging aerosol (TMC, the reference method used by vector control programmes), and householders’ bug notifications (HN). Triatomine infestations were evaluated in 103 sites of 54 houses, including domiciles, kitchens and storerooms.ResultsIn domiciles where Triatoma infestans was collected, sensitivity of each single method decreased from 79% by ST and 77% by HN, to 57% by TMC, and increased to 92% when ST was combined with HN. In peridomestic kitchens and storerooms, TMC was relatively as sensitive as ST and significantly more sensitive than HN. On average, the number of bugs recovered by ST was 0.94 times that collected by TMC. The ST mainly collected early-instar nymphs whereas TMC yielded late (larger) stages. Triatomines caught by ST had significantly lower mean weight-to-length ratios and lower blood-feeding rates than those caught by TMC, suggesting the ST intercepted and trapped vectors seeking a blood meal host.ConclusionsThe ST may effectively replace TMC for detecting T. infestans in domiciles, and is especially apt for early detection of low-density domestic infestations in the frame of community-based surveillance or elimination programmes; decision making on whether an area should be targeted for full-coverage insecticide spraying, and to corroborate that extant conditions are compatible with the interruption of vector-borne transmission.

Using the health belief model to identify communication opportunities to prevent Chagas disease in Southern Ecuador.

BackgroundChagas disease (CD) is a life-threatening illness caused by the protozoan parasite Trypanosoma cruzi, which is transmitted by triatomine bugs. Triatomine bugs inhabit poorly constructed homes that create multiple hiding spots for the bugs. Modifying the actual structure of a home, along with the homeowners’ practices, can reduce triatomine infestation. This research was designed to collect culturally-relevant information to develop a health campaign to decrease risk of CD transmission by promoting home maintenance and better hygiene in rural communities of southern Ecuador.Methods and main findingsThe Health Belief Model (HBM) guided focus group discussions and the interpretation of the results. Four focus groups ranging from 4 to 10 participants were conducted between May and June 2014 in three communities of Loja province in Southern Ecuador. A thematic analysis was used to identify within the data related to perceptions of susceptibility, severity, benefits, barriers and self-efficacy related to CD and its prevention. The results provide clear guidance for the development of Chagas-prevention messages.ConclusionData obtained emphasize the importance of standardizing messages presented to the communities for CD prevention. Messages should provide more information on the protective nature of the behaviors promoted for CD prevention; overcoming barriers such as cost and convenience, and build on facilitating factors, including community members’ interest on quality of life, protection of their families, and relationship with the land.

Spatial analyzes of triatomine infestation indices and their association to the actions of a Chagas disease program and environmental variables during a 5-year intervention period

Vector control of Chagas disease in the past decades has been mainly based on chemical control. Fundación Mundo Sano is implementing an Integral Chagas Program in a rural area of the Argentinean Gran Chaco Region since 2002. The objective of this study was to analyze both, temporal and spatial variation of infestation indices and their relation to the actions of the Program and environmental variables as land and vegetation cover changes, during a 5 year intervention period (2010–2014).Triatoma infestans infestation data from five rural localities from the Province of Santiago del Estero (Argentina) was analyzed in order to detect spatial aggregation. Differences in control effectiveness were observed between the peridomicile and intradomicile: infestation indices were higher in the peridomicile, recurrent infestation was present only in the peridomicile while low level infestation clusters were absent in the peridomicile. Cluster zones with low intradomestic infestation had larger proportions of bare soil and thin vegetation. In contrast, cluster zones with high intradomestic infestation had higher forest vegetation proportions and smaller cultivated area proportions.Spatial statistics analysis detected differences in cluster patterns between intra and peridomestic infestation suggesting that control actions should be based on geographical areas and not on political units. This work brings together different approaches to analyze infestation levels at the fine spatial scale, which could be used as a base for risk spatial stratification.

Distribution of triatomine species in domestic and peridomestic environments in central coastal Ecuador.

BackgroundAlthough the central coast of the Ecuador is considered endemic for Chagas disease, few studies have focused on determining the risk of transmission in this region. In this study we describe the triatomine household infestation in Manabí province (Central Coast region), determine the rate of Trypanosoma cruzi infection and study the risk factors associated with infestation by Rhodnius ecuadoriensis.Methodology/Principal findingsAn entomological survey found three triatomine species (Rhodnius ecuadoriensis, Panstrongylus rufotuberculatus and P. howardi) infesting domiciles in 47.4% of the 78 communities visited (total infestation rate of 4.5%). Four percent of domiciles were infested, and nymphs were observed in 77% of those domiciles. The three species were found in altitudes below 500 masl and in all ecological zones except cloud forest. Within the domicile, we found the three species mostly in bedrooms. Rhodnius ecuadoriensis and P. rufotuberculatus were abundant in bird nests, including chicken coops and P. howardi associated with rats in piles of bricks, in the peridomicile. Triatomine infestation was characterized by high rates of colonization, especially in peridomicile. Flagelates infection was detected in only 12% of the samples by microscopy and Trypanosoma cruzi infection in 42% of the examined triatomines by PCR (n = 372). The most important risk factors for house infestation by R. ecuadoriensis were ecological zone (w = 0.99) and presence of chickens (w = 0.96). Determinants of secondary importance were reporting no insecticide applications over the last twelve months (w = 0.86) and dirt floor (w = 0.70). On the other hand, wood as wall material was a protective factor (w = 0.85).Conclusion/SignificanceAccording the results, approximately 571,000 people would be at high risk for T. cruzi infection in Manabí province. A multidisciplinary approximation and the adhesion to a periodic integrated vector management (IVM) program are essential to guarantee sustainable preventive and control strategies for Chagas disease in this region.