Chagas Disease Control Program Research Articles

PRESENCE OF Triatoma tibiamaculata (PINTO) NYMPHS IN PERIDOMICILES, IN SALVADOR, BAHIA

Chagas disease is associated with the domiciliation of infected vectors migrating from their natural ecotopes. The appearance of nymphs in the peridomicile, in Salvador, Bahia, confirms the need for epidemiological surveillance. The vectors were captured from 2006 to 2009, by the population and by epidemiological field agents with the Chagas Disease Control Program. Three hundred and sixty two nymphs of the species Triatoma tibiamaculata (Pinto, 1926) were captured in the peridomicile and 13.5% of these nymphs were infected with Trypanosoma cruzi (Chagas, 1909). Nymphs werenear the houses, a possible risk for colonization. Surveillance of the peridomicile is an important element to prevent colonization by disease vectors.

Doença de Chagas: situação vetorial no município de Limoeiro do Norte – CE, no período de 2006 a 2009

In Brazil, among the endemic vector-borne diseases, Chagas disease has been considered one of the most important public health problems. The present study aimed at estimating the prevalence of triatomines infected with Trypanosoma cruzi in the city of Limoeiro do Norte, CE, Brazil. This investigation was conducted by consulting the archives of the Chagas disease control program of the Health District of Limoeiro do Norte for the period from 2006 to 2009. The study included dead or alive, adults and nymphs triatomines, which where captured during the investigated period. During the four-year study, 2,863 specimens of nymphs and adults insects were captured from the domestic and peridomestic areas; 2,756 were examined, representing 96.3 % of collected specimens. The insect infection rate was 7.9 % in four-year study. The number of captured nymphs was nearly three times higher than the number of adults; however the number of nymphs infected with the flagellate (5.30 %) was lower than the number of adults form (15.85 %). Limoeiro do Norte showed a high risk for Chagas disease transmission, suggesting that the control actions should be intensified in this city to prevent the disease transmission and the vector spread.

Triatomines in dwellings and outbuildings in an endemic area of Chagas disease in northeastern Brazil

The present study identified the triatomines collected in intra and peri-domestic environments, observed the occurrence of Trypanosoma cruzi infection in triatomines and correlated this information with housing conditions and the fauna associated with the rural areas of the City of Itabaianinha, located in the State of Sergipe, Brazil. Quarterly visits were conducted between March 2009 and March 2010, and the homes to be visited for the active search of insects were determined by random selection. In each housing unit, the insects were collected by a manual search with a metal clip and flashlight to inspect openings and cavities, with a collection time of one hour/home/individual. The Pirisa® dislodge chemical was used to force the insects to leave their ecotopes. Analysis of the intestinal contents of triatomines was performed in the laboratory to establish the presence of Trypanosomatidae. Of the 103 dwellings surveyed, 17.5% were infested with Panstrongylus megistus. The village of Mutuca exhibited the highest infestation rate (38.1%). All the villages with relevant infestation rates were situated in the northern area of the city. The highest percentage of vector infection was found in the village of Água Boa (56.5%). The rural dwellings were found to be primarily brick or wooden house with or without roughcast or plastered walls, and the outbuilding most frequently associated with triatomines was the chicken run. These results emphasise the need for broader vector control and surveillance and for educational campaigns in the context of the Chagas Disease Control Program.

Prevalence ofTrypanosoma cruziin Dogs (Canis familiaris) and Triatomines During 2008 in a Sanitary Region of the State of Mexico, Mexico

American trypanosomiasis is a public health problem in Latin America and southern parts of the United States. Infection in triatomines (vector) and domestic dogs (reservoir host) is a good indicator of Trypanosoma cruzi circulation and human risk of infection. The State of Mexico, Mexico, has been considered free of T. cruzi, and no detailed epidemiologic study has been conducted to assess the intricacies of the transmission cycle of the parasite in the region. Such studies would enhance our understanding of the epidemiology of T. cruzi infection in this geographic region and provide regional sanitary authorities with stronger fundamental knowledge for making decisions and allocating funds for Chagas disease control programs in the State of Mexico. The objective of this study was to determine the prevalence of T. cruzi infection in dogs (seroprevalence) and triatomines (fecal parasites) in a previously identified, discrete endemic region of parasite circulation and to widen our studies in the Tejupilco Sanitary Region located in the southern part of the State of Mexico. Dog blood samples (n=102) were analyzed for the presence of anti-T. cruzi antibodies by two assays, namely indirect hemagglutination assay and enzyme-linked immunosorbent assay. Triatomines (n=88) were collected and fecal aliquots were analyzed for the presence of parasites by light microscopy. Average seroprevalence in dogs in the Tejupilco Sanitary region was 24.5%, and the overall triatomine infection rate was 34.01%. Triatoma pallidipennis was the only triatomine species found in this region. Our data demonstrate that T. cruzi is actively circulating in the Tejupilco Sanitary Region and emphasize the requirement for epidemiologic surveillance programs throughout the putative endemic areas of the State of Mexico.

Entomological surveillance of Chagas disease in Berilo municipality, Jequitinhonha Valley, State of Minas Gerais, Brazil

This study aimed to evaluate the Chagas Disease Control Program which has operated since 1982 in the municipality of Berilo in the Jequitinhonha Valley, Minas Gerais, Brazil, based on evaluation of 5,242 domiciliary units (DUs) and 7,807 outbuildings over an eight-year period of epidemiological surveillance implanted in 1997. A total of 391 triatomines (280 Panstrongylus megistus and 111 Triatoma pseudomaculata) were captured, indicating the continued predominance of the former species. However, Triatoma pseudomaculata is clearly becoming more important in this region, with intradomiciliary colonies being detected in recent years. Entomological parameters, such as dispersion (17%) and intradomiciliary infestation (0.15%) indices, are compatible with the results of the epidemiological surveillance. The majority of DUs were of construction type A (plaster over bricks) or C (plaster over adobe). Twenty-five percent of the inhabitants of the DUs infested by triatomines were reactive in ELISA, IHA and IIF tests for Trypanosoma cruzi antigens.

Surveillance of Chagas disease vectors in municipalities of the state of Ceará, Brazil

The present study aimed to analyse the dwelling infestation rates and the distribution and natural Trypanosoma cruzi infection rates, among triatomines captured in the 13 municipalities of the state of Ceará. The records relating to the capture of intradomicile and peridomicile triatomines during the Chagas disease control program of 1998-2008 were available. Among the triatomines captured and in all of the municipalities studied, Triatoma brasiliensis presented the highest incidence in intradomicile and Triatoma pseudomaculata in peridomicile and some were positive for infection by T. cruzi. We emphasise that it is important to have sustainable epidemiological surveillance in the region, since when the control measures decreased, the incidence of T. pseudomaculata in intradomicile grew.

Avaliação de conhecimentos e práticas que adultos e crianças têm acerca da doença de Chagas e seus vetores em região endêmica de Minas Gerais, Brasil

Despite the success of the Chagas Disease Control Program (PCCD) in Brazil, some endemic areas have experienced difficulty in maintaining the program's activities, especially after the health system's decentralization, since the sustainability of control measures for Chagas disease and vectors is known to depend on information and community participation. This study aimed to analyze knowledge and practices related to vectors and Chagas disease in Bambuí, Minas Gerais State, Brasil. The population's knowledge was tested with a questionnaire, accompanied by six illustrations of triatomine bugs for identification. Both adults and primary and secondary schoolchildren in rural areas of the county participated in the research. The Bambuí population showed good overall knowledge on triatomines and Chagas disease in both groups (adults and children), although the concepts were limited to preventing the insect vector from invading houses. The results emphasize the importance of educational campaigns in the context of the program as a fundamental component of community participation in Chagas disease vector control.

Sustainability of vector control strategies in the Gran Chaco Region: current challenges and possible approaches.

Sustainability has become a focal point of the international agenda. At the heart of its range of distribution in the Gran Chaco Region, the elimination of Triatoma infestans has failed, even in areas subject to intensive professional vector control efforts. Chagas disease control programs traditionally have been composed of two divorced entities: a vector control program in charge of routine field operations (bug detection and insecticide spraying) and a disease control program in charge of screening blood donors, diagnosis, etiologic treatment and providing medical care to chronic patients. The challenge of sustainable suppression of bug infestation and Trypanosoma cruzi transmission can be met through integrated disease management, in which vector control is combined with active case detection and treatment to increase impact, cost-effectiveness and public acceptance in resource-limited settings. Multi-stakeholder involvement may add sustainability and resilience to the surveillance system. Chagas vector control and disease management must remain a regional effort within the frame of sustainable development rather than being viewed exclusively as a matter of health pertinent to the health sector. Sustained and continuous coordination between governments, agencies, control programs, academia and the affected communities is critical.

Avaliação do Programa de Controle da Doença de Chagas em relação à presença de Panstrongylus megistus na região centro-oeste do Estado de Minas Gerais, Brasil

The Brazilian National Chagas Disease Control Program (PCDCh) is currently in the epidemiological surveillance phase and poses one of the principal challenges for maintaining and improving surveillance. With the decentralization of health actions, leading to the transfer of responsibilities over the control of endemic diseases to the State and Municipal governments, some municipalities have faced difficulties in implementing the Program, since they lack experience in controlling this disease. This study analyzes the current situation with epidemiological surveillance of Chagas disease in 54 municipalities (counties) in central-western Minas Gerais State, with a view towards evaluation and improvement of the process. From July 2003 to July 2007, 776 captures were performed, totaling 1,390 triatomine bugs from 37 municipalities. The most prevalent species was Panstrongylus megistus (99.3% of the specimens captured). A total of 8.3% of the specimens were positive for Trypanosoma cruzi-like flagellates. Distribution of the specimens differed between municipalities, and the article discusses some reasons for these differences. As a whole, the findings strongly suggest the need to improve Chagas disease epidemiological surveillance in the region.

Antibody responses of domestic animals to salivary antigens of Triatomainfestans as biomarkers for low-level infestation of triatomines

Hematophagous arthropods such as Triatoma infestans, the vector of Trypanosoma cruzi, elicit host-immune responses during feeding. Characterization of antibody responses to salivary antigens offers the potential to develop immunologically based monitoring techniques for exposure to re-emergent triatomine bug populations in peridomestic animals. IgG-antibody responses to the salivary antigens of T. infestans have been detected in chickens as soon as 2 days after the first exposure to five adult bugs. Chickens and guinea pigs regularly exposed to this number of triatomines showed a significantly lower anti-saliva antibody titre than animals exposed to 25 adults and fifth instars of four different T. infestans strains originating from Bolivia and from Northern Chile. Highly immunogenic salivary antigens of 14 and 21 kDa were recognised by all chicken sera and of 79 kDa by all guinea pig sera. Cross-reactivity studies using saliva or salivary gland extracts from different hematophagous species, e.g. different triatomines, bed bugs, mosquitoes, sand flies and ticks, as well as chicken sera exposed to triatomines and mosquitoes, demonstrated that the 14 and 21 kDa salivary antigens were only found in triatomines. Sera from peridomestic chickens and guinea pigs in sites of known T. infestans challenge in Bolivia also recognised the 14 and 21 kDa antigens. These represent promising epidemiological markers for the detection of small numbers of feeding bugs and hence may be a new tool for vector surveillance in Chagas disease control programs.

Combining Residual Insecticide Spraying Campaigns with Targeted Detection and Specific Chemotherapy for Trypanosoma cruzi Infection in Children

Combining Residual Insecticide Spraying Campaigns with Targeted Detection and Specific Chemotherapy for Trypanosoma cruzi Infection in Children

Targeted screening strategies to detect Trypanosoma cruzi infection in children.

BackgroundMillions of people are infected with Trypanosoma cruzi, the causative agent of Chagas disease in Latin America. Anti-trypanosomal drug therapy can cure infected individuals, but treatment efficacy is highest early in infection. Vector control campaigns disrupt transmission of T. cruzi, but without timely diagnosis, children infected prior to vector control often miss the window of opportunity for effective chemotherapy.Methods and FindingsWe performed a serological survey in children 2–18 years old living in a peri-urban community of Arequipa, Peru, and linked the results to entomologic, spatial and census data gathered during a vector control campaign. 23 of 433 (5.3% [95% CI 3.4–7.9]) children were confirmed seropositive for T. cruzi infection by two methods. Spatial analysis revealed that households with infected children were very tightly clustered within looser clusters of households with parasite-infected vectors. Bayesian hierarchical mixed models, which controlled for clustering of infection, showed that a child's risk of being seropositive increased by 20% per year of age and 4% per vector captured within the child's house. Receiver operator characteristic (ROC) plots of best-fit models suggest that more than 83% of infected children could be identified while testing only 22% of eligible children.ConclusionsWe found evidence of spatially-focal vector-borne T. cruzi transmission in peri-urban Arequipa. Ongoing vector control campaigns, in addition to preventing further parasite transmission, facilitate the collection of data essential to identifying children at high risk of T. cruzi infection. Targeted screening strategies could make integration of diagnosis and treatment of children into Chagas disease control programs feasible in lower-resource settings.

Vigilância epidemiológica da doença de Chagas em programa descentralizado: avaliação de conhecimentos e práticas de agentes municipais em região endêmica de Minas Gerais, Brasil

This study aimed to evaluate the epidemiological surveillance of Chagas disease in the central-western region of Minas Gerais State, Brazil, based on knowledge and practice among municipal health agents working in the Chagas Disease Control Program. Thirty-five municipalities (counties) were visited, with meetings and application of a questionnaire on knowledge, practice, and difficulties in conducting the surveillance work. Twenty-six agents were on temporary (annual) contracts, and only two had job stability. 77.1% of the agents commented that the local population had difficulty identifying the vector insects (triatomines). Twenty-three employees stated that the municipal governments provided adequate conditions for conducting the surveillance program, although 27 made suggestions, particularly requesting more educational materials, better wages, and greater appreciation of their work by the municipal governments. Such suggestions are crucial to the consolidation of the program's results.

RISK FACTORS FOR TRYPANOSOMA CRUZI HUMAN INFECTION IN BARINAS STATE, VENEZUELA

This study attempted to quantify the transmission of Trypanosoma cruzi in children less than 15 years of age in Barinas State, Venezuela and investigate risk factors for infection. Among 3,296 children, 4 (0.12%) were seropositive. The mother of one child also was also seropositive, which suggested that congenital transmission is a possible risk factor for Chagas disease in this area. Seroprevalence among the dwellers of 10 localities was 3.3%. Rhodnius prolixus was detected in 7 localities and in 8% of 125 dwellings. A multivariate logistic regression model showed that infection was associated with age, a dirt floor, and distance from houses to palm trees. The risk of infection is increased by the presence of adventitious sylvatic R. prolixus and transient or residual colonies. Insecticide spraying does not seem justified in this scenario, a finding that was also observed in other Latin American countries. New methods are therefore needed for Chagas disease control programs.

Vigilância entomológica da doença de Chagas na região centro-oeste de Minas Gerais, Brasil, entre os anos de 2000 e 2003

In Minas Gerais State, Brazil, after the elimination of Triatoma infestans by the Brazilian Chagas Disease Control Program, some triatomine species, such as Panstrongylus megistus, have merited the attention of entomological surveillance authorities. After the decentralization of the Brazilian health system, certain administrative and operational difficulties have been observed in some municipalities (counties). This study aims to evaluate entomological surveillance for Chagas disease in the 54 municipalities supervised by the Division of Decentralized Health Activities in Divinopolis, Minas Gerais, from 2000 to 2003. In 46 municipalities, 1,531 triatomines were captured, of which 94.1% were P. megistus. The infection rate for T. cruzi in the vectors was 1.3%. A total of 850 reports were received and 835 site visits were conducted, showing that the program is active and efficient in the majority of the municipalities analyzed. The importance of the maintenance and improvement of entomological surveillance in the region was demonstrated, since triatomine bugs continue to invade (and can colonize) the domiciliary environment, although with low density.

Enfermedad de Chagas en Argentina: herramientas para que los escolares vigilen y determinen la presencia de factores de riesgo en sus viviendas

The objective of this paper was to validate tools for schoolchildren to help control Chagas disease vectors in their own homes. Two types of tables were produced, one reporting on the presence of risk factors in residences and the other to record the presence of triatomines. The materials were tested in the field by 100 students from an endemic area in Argentina and validated by technical personnel. The results obtained by students concerning the percentage of households with risk factors and vector-positive residences were similar to those obtained by the technical personnel. This information allowed teachers to classify the risk levels in the residences as at "high-risk", "risk", or "no risk". The information provides an important aid for health workers, and it is therefore recommended to include this educational strategy in the surveillance phase of the Chagas disease control program.

High Household Infestation Rates by Synanthropic Vectors of Chagas Disease in Southern Ecuador

Entomological surveys were conducted in five rural communities (138 domiciliary units [DUs]) in the southern Andes of Ecuador. Adobe walls and ceramic tile roofs were predominant construction materials. A 35% house infestation rate with Panstrongylus chinai (Del Ponte, 1929) (0.7%), Panstrongylus rufotuberculatus (Champion, 1899) (0.7%), Rhodnius ecuadoriensis (Lent & León, 1958) (27%), and/or Triatoma carrioni (Larrousse, 1926) (7%) was found. Adults and nymphs of R. ecuadoriensis and T. carrioni were found in intradomiciliary and peridomiciliary areas. Breeding triatomine colonies were present in 85% of infested DUs, and the average insect crowding was 52+/-113 triatomine bugs per infested house. T. cruzi-like organisms were found by microscopic examination in the feces or hindgut but not the salivary glands of 4% of examined R. ecuadoriensis and 12% T. carrioni. Serological tests detected a general anti-T. cruzi antibody seroprevalence of 3.9% (n = 1136). Only 2% of individuals had heard of Chagas disease, and although triatomines were reported as a major nuisance by the population they were not considered vectors of disease. Additional baseline field research is needed for the design and implementation of a Chagas disease control program in the region.

Can wild foci in Bolivia jeopardize Chagas disease control efforts?

The expected success of Chagas disease control programs in the Southern Cone countries relied on the assumption that Triatoma infestans, the main domestic vector, did not maintain silvatic foci except in the Cochabamba valley in Bolivia. Recent fieldwork revealed that wild populations of this vector are much more widespread throughout Bolivia than previously thought. Therefore, it is important to find out whether these silvatic populations could jeopardize control efforts in Bolivia, and to investigate their possible occurrence in neighboring regions of Paraguay and Argentina.

Triatomine infestation and vector-borne transmission of Chagas disease in northwest and central Parana, Brazil.

Triatomine infestation, prevalence of T. cruzi antibodies in humans and domestic animals, and variables potentially associated with the presence of triatomines in a rural domiciliary unit (DU) were investigated in nine municipalities and one district of Parana, Brazil, from June 1996 to February 2000. DUs were defined as all houses and annexes on a given piece of property. Blood samples from human volunteers, dogs, and cats were submitted to indirect immunofluorescence. An epidemiological form was completed for each DU. A logistic model was adopted in order to identify associations. Seven out of nine municipalities were positive for triatomines. T. infestans was not captured, but T. sordida, P. megistus, and R. neglectus were. Different variables were considered decisive for the presence of triatomines across the municipalities: proximity to residual wooded areas, i.e. either scrub forest (capoeira) or islands of residual forest (slightly dense vegetation), longer time of residence, existence of inhabited houses, and past DU infestation. In order to ensure proper continuation of the recommended Chagas disease control program, entomo-epidemiological surveillance measures need to be maintained.

Evaluation of risk factors for rural infestation by Triatoma pallidipennis (Hemiptera: Triatominae), a Mexican vector of Chagas disease.

Control of Chagas disease requires control of its triatomine vectors, which requires an understanding of the determinants of infestation. Twenty-seven household environmental characteristics in the town of Chalcatzingo, Morelos, were analyzed for association with infestation by Triatoma pallidipennis, the predominant local vector. Data were obtained through timed household searches for triatomines and surveys that characterized intradomicile and peridomicile environments. Of the households surveyed, 28.4% were infested by T. pallidipennis. Cross-sectional multivariate logistic regression analyses were performed that regressed infestation on environmental variables. Of the 530 households in the town, 84% had sufficient data to be included. Adobe walls, agricultural products, junk piles, lack of bednets, and number of rabbits were significantly associated with intradomiciliary infestation. Junk piles and numbers of dogs, cats, and rabbits were significantly associated with peridomiciliary infestation. Junk piles, agricultural products, and numbers of cats, rabbits, and birds were significantly associated with overall infestation. Unexpectedly, presence of stone piles was not associated with infestation. The results of this study provide information for designing Chagas disease control programs in rural Mexican areas infested by T. pallidipennis.