Risk Of Chagas Disease Research Articles

Projected Future Distributions of Vectors of Trypanosoma cruzi in North America under Climate Change Scenarios

BackgroundChagas disease kills approximately 45 thousand people annually and affects 10 million people in Latin America and the southern United States. The parasite that causes the disease, Trypanosoma cruzi, can be transmitted by insects of the family Reduviidae, subfamily Triatominae. Any study that attempts to evaluate risk for Chagas disease must focus on the ecology and biogeography of these vectors. Expected distributional shifts of vector species due to climate change are likely to alter spatial patterns of risk of Chagas disease, presumably through northward expansion of high risk areas in North America.Methodology/Principal FindingsWe forecast the future (2050) distributions in North America of Triatoma gerstaeckeri and T. sanguisuga, two of the most common triatomine species and important vectors of Trypanosoma cruzi in the southern United States. Our aim was to analyze how climate change might affect the future shift of Chagas disease in North America using a maximum entropy algorithm to predict changes in suitable habitat based on vector occurrence points and predictive environmental variables. Projections based on three different general circulation models (CCCMA, CSIRO, and HADCM3) and two IPCC scenarios (A2 and B2) were analyzed. Twenty models were developed for each case and evaluated via cross-validation. The final model averages result from all twenty of these models. All models had AUC >0.90, which indicates that the models are robust. Our results predict a potential northern shift in the distribution of T. gerstaeckeri and a northern and southern distributional shift of T. sanguisuga from its current range due to climate change.Conclusions/SignificanceThe results of this study provide baseline information for monitoring the northward shift of potential risk from Chagas disease in the face of climate change.

Chagas disease in Australia and New Zealand: risks and needs for public health interventions

International migration has changed the global distribution of Chagas disease, with the emerging importance of non-endemic regions. We aimed at better documenting the Australia and New Zealand risk of Chagas disease and needs for interventions. We reviewed Chagas disease-related evidences, policies and practices in Australia and New Zealand and calculated the estimated prevalence. Australia hosts a rapidly growing population at risk and had 1928 infected residents in 2011; New Zealand had 98 in 2006. These figures underestimate the real situation, as they do not consider non-permanent residents. The only existing policy in both countries is the identification of blood donors with a history of or a risk of infection via questionnaire. There is no programme of detection and care of patients. The lifetime economic burden of disease for society is potentially very high. Chagas disease is an emerging health risk with potential high human and economic costs in Australia and New Zealand in the absence of public health attention. Implementing strategies to screen high-risk groups and prevent transmission should be considered. Moreover, migration between the Western Pacific and Chagas endemic regions and the presence of vectors means this risk applies in the whole region.

The Significance of Electrocardiographic Abnormalities and Serology for T. cruzi Infection

Background: Electrocardiography (EKG) is a basic complementary exam in the evaluation patients with Chagas disease (CD), where findings can precede symptoms and physical examination abnormalities. Objective: To correlate positive Chagas serology and electrocardiographic abnormalities associated with chronic chagasic cardiomyopathy. Method: We evaluated the correlation between results of an ELISA using crude antigen (TcLys) and recombinant antigen (TcF) with the presence of EKG disturbances, within a cohort of individuals with either epidemiologic risk or clinical symptoms suggestive of CD, sent to our Laboratory for Tropical Diseases for testing in state of Bahia, Brazil. Results: 84 individuals had a positive ELISA using TcLys or TcF antigen. Overall, 49 patients (58.3%) were symptomatic with CD, 42 (85.7%) with isolated evidence of the cardiac form, one (2.0%) with megacolon and mixed (megaviscera and cardiac) in six (12.2%). TcLys ELISA was positive in 45/49 (91.8%) and TcF in 42/49 (85.7%) of the symptomatic patients. The most common EKG abnormality, Complete Right Bundle Branch Block (CRBBB), was seen in 47/84 patients (56.0%) of the patients. Interestingly, in 11/47 (23.4%) of the patients with CRBBB, serologies were discordant. Conclusions: EKG plays a key role in the initial evaluation of patients with positive Chagas serology using crude or recombinant antigens. Individuals with positive serology should be carefully followed with periodical cardiac medical examination to early detect EKG abnormality compatible with CD.

Lower Richness of Small Wild Mammal Species and Chagas Disease Risk

A new epidemiological scenario involving the oral transmission of Chagas disease, mainly in the Amazon basin, requires innovative control measures. Geospatial analyses of the Trypanosoma cruzi transmission cycle in the wild mammals have been scarce. We applied interpolation and map algebra methods to evaluate mammalian fauna variables related to small wild mammals and the T. cruzi infection pattern in dogs to identify hotspot areas of transmission. We also evaluated the use of dogs as sentinels of epidemiological risk of Chagas disease. Dogs (n = 649) were examined by two parasitological and three distinct serological assays. kDNA amplification was performed in patent infections, although the infection was mainly sub-patent in dogs. The distribution of T. cruzi infection in dogs was not homogeneous, ranging from 11–89% in different localities. The interpolation method and map algebra were employed to test the associations between the lower richness in mammal species and the risk of exposure of dogs to T. cruzi infection. Geospatial analysis indicated that the reduction of the mammal fauna (richness and abundance) was associated with higher parasitemia in small wild mammals and higher exposure of dogs to infection. A Generalized Linear Model (GLM) demonstrated that species richness and positive hemocultures in wild mammals were associated with T. cruzi infection in dogs. Domestic canine infection rates differed significantly between areas with and without Chagas disease outbreaks (Chi-squared test). Geospatial analysis by interpolation and map algebra methods proved to be a powerful tool in the evaluation of areas of T. cruzi transmission. Dog infection was shown to not only be an efficient indicator of reduction of wild mammalian fauna richness but to also act as a signal for the presence of small wild mammals with high parasitemia. The lower richness of small mammal species is discussed as a risk factor for the re-emergence of Chagas disease.

Combining geospatial analysis and exploratory study of triatomine ecology to evaluate the risk of Chagas disease in a rural locality

The use of geo-spatial analysis to anticipate transmission risk for Chagas disease was tested in a rural area of northeast Brazil in an approach that combined geo-referencing and exploratory study of triatomine infestation, including related elements such as the environment and hosts. A total of 617 triatomine specimens, mainly Triatoma brasiliensis, were captured, exhibiting an overall T. cruzi positivity of 44.4%. Layer analysis indicated that the greatest transmission risk to man was associated with woodpiles. The buffer area generated contained uninhabited dwellings teeming with bats and positive bugs. Other locations outside the buffer, near uninhabited dwellings housing cattle, contained colonies of triatomines harboring T. cruzi. The results indicate that local residents’ activities themselves favor the development of risk areas for Chagas disease.

Comment on Zoonoses in the Bedroom (Response)

To the Editor: In response to Chomel and Sun (1), we would like to correct potentially misleading representations of risk factors for parasitic diseases. The authors correctly described risk for Chagas disease from exposure to infected insect vectors but included Chagas disease in the table, “Zoonoses acquired by close contact with pet, 1974–2010.” The bloodborne protozoan that causes Chagas disease is transmitted not by contact with an infected mammal but by contact with a vector insect that has bitten an infected mammal (2). For some parasitic zoonoses, contact with pets may not be a major source of infection. Molecular studies indicate that risk for human infection with Giardia and Cryptosporidium spp. from dogs and cats may be lower than previously believed. Infections with these parasites are usually with species-specific genotypes. Human infections with assemblages C, D (dog specific), and F (cat specific) of G. duodenalis have not been confirmed. Infections with assemblages A or B have been reported for humans and other animal species, including dogs and cats, but no direct transmission has been documented (3,4). Most human cryptosporidial infections are caused by C. hominis and C. parvum (5); a smaller percentage are caused by C. canis and C. felis. Human infection with Toxocara canis or T. cati occurs when embryonated eggs are ingested; however, embryonation requires 2–4 weeks in the environment, suggesting that the risk from eggs in pet fur may be less than risk from exposure to eggs in contaminated soil. Other more serious zoonotic parasitic disease risks from contact with pet feces, including toxoplasmosis, are mentioned only briefly, if at all. Physicians need information that accurately communicates zoonotic parasitic disease risks to their patients. However, inaccurate or overstated risk communication can also lead to unnecessary prevention efforts and misdirected concerns about dogs and cats as sources of disease.

Spatial distribution of triatomines (Reduviidae: Triatominae) in urban areas of the city of Salvador, Bahia, Brazil

Environmental changes have a strong influence on the emergence and/or reemergence of infectious diseases. The city of Salvador, Brazil--currently the focus of a housing boom linked to massive deforestation--is an example in point as the destruction of the remaining areas of the Atlantic Forest around the city has led to an increased risk for Chagas disease. Human domiciles have been invaded by the triatomine vectors of Trypansoma cruzi, the flagellate protozoan causing Chagas disease, a problem of particular concern in urban/suburban areas of the city such as the Patamares sector in the north-east, where numbers of both the vector and human cases of the disease have increased lately. To control and prevent further deterioration of the situation, the control programme for Chagas disease, developed by the Bahia Center for Zoonosis Control, has divided the area into a grid of designated surveillance units (ZIs) that are subjected to vector examination. In six out of 98 of these ZIs, 988 triatomes were collected and georeferenced during the 3-year period between 2006 and 2009. The hottest months, that are also generally the driest, showed the highest numbers of triatomines with Triatoma tibiamaculata being the predominant species (98.3%) with Panstrongylus geniculatus present only occasionally (0.6%). Fifty-four percent of all triatomines captured were found inside the homes, and 48.6% out of 479 individuals in the affected ZIs selected for analysis tested positive for T. cruzi infection. The study presented here is a pioneering initiative to map the spatial distribution of triatomines based on geographical information systems with the additional aim of contributing to an expanded knowledge-base about T. cruzi and its vectors in urban areas and raise public health awareness of the risks involved.

Remembering en bloc double-lung transplantation

the transplanted and explanted hearts did not show T cruzi forms. Despite starting benznidazole on Day 46), her clinical condition worsened, skin lesions became bullous and necrotic (Fig 1, center), and hemophagocytic syndrome developed. She died on Day 53 of multiple organ failure associated with refractory shock and Serratia marcescens bacteriemia. Autopsy did not show graft rejection. T cruzi reactivation affects 27% to 90% of Chagasic heart recipients, usually within 1 to 24 months postoperatively, and most recipients suffer 2 or more episodes. Benznidazole prophylaxis before or after transplant does not prevent reactivation. This patient’s fatally delayed diagnosis has several causes. Chagas disease is still rare in Europe, and clinicians are not familiar with its presentation. Most patients present as asymptomatic or with mild cardiomyopathy. In Europe, Latino American immigrants may consult under a second nationality (Spain, Portugal), thus blinding clinicians to epidemiologic clues on the risk of Chagas disease. Recent guidelines recommend that screening in organ donors should be considered in regions harboring significant populations of immigrants at risk. Considering this emerging problem, we recommend measures to be taken in Europe:

Chagas disease risk in Texas.

BackgroundChagas disease, caused by Trypanosoma cruzi, remains a serious public health concern in many areas of Latin America, including México. It is also endemic in Texas with an autochthonous canine cycle, abundant vectors (Triatoma species) in many counties, and established domestic and peridomestic cycles which make competent reservoirs available throughout the state. Yet, Chagas disease is not reportable in Texas, blood donor screening is not mandatory, and the serological profiles of human and canine populations remain unknown. The purpose of this analysis was to provide a formal risk assessment, including risk maps, which recommends the removal of these lacunae.Methods and FindingsThe spatial relative risk of the establishment of autochthonous Chagas disease cycles in Texas was assessed using a five–stage analysis. 1. Ecological risk for Chagas disease was established at a fine spatial resolution using a maximum entropy algorithm that takes as input occurrence points of vectors and environmental layers. The analysis was restricted to triatomine vector species for which new data were generated through field collection and through collation of post–1960 museum records in both México and the United States with sufficiently low georeferenced error to be admissible given the spatial resolution of the analysis (1 arc–minute). The new data extended the distribution of vector species to 10 new Texas counties. The models predicted that Triatoma gerstaeckeri has a large region of contiguous suitable habitat in the southern United States and México, T. lecticularia has a diffuse suitable habitat distribution along both coasts of the same region, and T. sanguisuga has a disjoint suitable habitat distribution along the coasts of the United States. The ecological risk is highest in south Texas. 2. Incidence–based relative risk was computed at the county level using the Bayesian Besag–York–Mollié model and post–1960 T. cruzi incidence data. This risk is concentrated in south Texas. 3. The ecological and incidence–based risks were analyzed together in a multi–criteria dominance analysis of all counties and those counties in which there were as yet no reports of parasite incidence. Both analyses picked out counties in south Texas as those at highest risk. 4. As an alternative to the multi–criteria analysis, the ecological and incidence–based risks were compounded in a multiplicative composite risk model. Counties in south Texas emerged as those with the highest risk. 5. Risk as the relative expected exposure rate was computed using a multiplicative model for the composite risk and a scaled population county map for Texas. Counties with highest risk were those in south Texas and a few counties with high human populations in north, east, and central Texas showing that, though Chagas disease risk is concentrated in south Texas, it is not restricted to it.ConclusionsFor all of Texas, Chagas disease should be designated as reportable, as it is in Arizona and Massachusetts. At least for south Texas, lower than N, blood donor screening should be mandatory, and the serological profiles of human and canine populations should be established. It is also recommended that a joint initiative be undertaken by the United States and México to combat Chagas disease in the trans–border region. The methodology developed for this analysis can be easily exported to other geographical and disease contexts in which risk assessment is of potential value.

Distribución geográfica y ecoepidemiología de la fauna de triatominos (Reduviidae: Triatominae) en la Isla Margarita del departamento de Bolívar, Colombia

Information concerning to triatomine diversity and some eco-epidemiologic aspects on Margarita Island has been recorded only from two of the five counties on the island. Knowledge about species habitat and their natural infection is essential to establish the risk for Chagas disease in endemic areas. The distribution of triatomine insect fauna and its infection with Trypanosoma cruzi was described in order to establish and to stratify the risk of Chagas disease transmission. Each of the 5 counties on Margarita Island were surveyed for triatomid insects inside and outside each dwelling. In the extradomicilary area, searches were conducted in the palms and bird nests located within forests and in pastures near domiciles. Infection with T. cruzi was determined amplifying by PCR the DNA extracted from triatomine feces. Five species of Reduviidae were recovered among the 1,154 triatomines captured in the 5 counties. Triatoma maculata and Rhodnius pallescens showed high infection rates within dwellings and as well as in the peridomestic areas in Mompós and Talaigua Nuevo. On the palm trees, only R. pallescens and Eratyrus cuspidatus were found infected, and only in San Fernando and Margarita. In Cicuco, only R. pallescens was infected. Presence of Triatoma dimidiata was also ascertained. Infected triatomines were present in houses and on palm trees in all counties on the island. These observations indicate a potential risk of Chagas across the entire island; furthermore the presence of T. dimidiata, a very efficient Chagas vector, emphasizes the need to establish its epidemiological status on the island.

Physician Awareness of Chagas Disease, USA

Physician Awareness of Chagas Disease, USA

Chagas disease, migration and community settlement patterns in Arequipa, Peru.

BackgroundChagas disease is one of the most important neglected tropical diseases in the Americas. Vectorborne transmission of Chagas disease has been historically rare in urban settings. However, in marginal communities near the city of Arequipa, Peru, urban transmission cycles have become established. We examined the history of migration and settlement patterns in these communities, and their connections to Chagas disease transmission.Methodology/Principal FindingsThis was a qualitative study that employed focus group discussions and in-depth interviews. Five focus groups and 50 in-depth interviews were carried out with 94 community members from three shantytowns and two traditional towns near Arequipa, Peru. Focus groups utilized participatory methodologies to explore the community's mobility patterns and the historical and current presence of triatomine vectors. In-depth interviews based on event history calendars explored participants' migration patterns and experience with Chagas disease and vectors. Focus group data were analyzed using participatory analysis methodologies, and interview data were coded and analyzed using a grounded theory approach. Entomologic data were provided by an ongoing vector control campaign. We found that migrants to shantytowns in Arequipa were unlikely to have brought triatomines to the city upon arrival. Frequent seasonal moves, however, took shantytown residents to valleys surrounding Arequipa where vectors are prevalent. In addition, the pattern of settlement of shantytowns and the practice of raising domestic animals by residents creates a favorable environment for vector proliferation and dispersal. Finally, we uncovered a phenomenon of population loss and replacement by low-income migrants in one traditional town, which created the human settlement pattern of a new shantytown within this traditional community.Conclusions/SignificanceThe pattern of human migration is therefore an important underlying determinant of Chagas disease risk in and around Arequipa. Frequent seasonal migration by residents of peri-urban shantytowns provides a path of entry of vectors into these communities. Changing demographic dynamics of traditional towns are also leading to favorable conditions for Chagas disease transmission. Control programs must include surveillance for infestation in communities assumed to be free of vectors.

The potential for emergence of Chagas disease in the United States

To determine the risk for Chagas disease (American trypanosomiasis) in the United States, the characteristics that make the triatomine vector effective and the areas most at risk for transmission were delineated. In addition, the status of Chagas disease awareness among physicians in areas with a potential risk for the disease was determined. A geographical information system (GIS) was used to analyze three triatomine species within the United States known to harbor Trypanosoma cruzi and that exhibit qualities of domesticity. An analysis of the minimum temperature threshold for increased triatomine activity delineates the current population at increased risk, and by incorporating temperature predictions for 2030, the population at risk under a future climate scenario was also delineated. Considering both environmental and social factors, a vignette-based physician survey, based on the results of the GIS analysis, was used to gauge the level of awareness of Chagas disease within the delineated higher risk range. The current area at increased risk for Chagas disease includes much of the southern United States, and the higher risk range is expected to expand into the central United States based upon the 1 degrees C (1.8 degrees F) increase in temperature predicted by the Intergovernmental Panel on Climate Change (IPCC) by the year 2030. Survey results indicate a limited consideration of Chagas disease during differential diagnosis, illustrating that the low number of Chagas disease cases discovered in the United States may be attributable to a lack of disease awareness as opposed to a lack of disease threat. This study combines GIS and survey analyses to evaluate the role that temperature variability and disease awareness among physicians play in the potential emergence of Chagas disease in the United States. This approach indicates that there is a potential for Chagas disease to emerge in the United States.

Awareness of stroke risk in chagasic stroke patients

Reduction in stroke risk may depend on the general population's knowledge of stroke. In South America, chagasic myocardiopathy is independently associated with ischemic stroke. The aim of this study was to evaluate awareness of Chagas' disease (CD) as a stroke risk factor and to determine the frequency of stroke patients that are diagnosed as having CD after stroke. Eighty CD stroke patients and 140 non-chagasic stroke patients (53.2% males; mean age 60 years), consecutively admitted to the hospital during 2005 were interviewed with a questionnaire. Demographic variables included age, sex, ethnicity, education, previous history of stroke, vascular risk factors, social background information and several questions regarding awareness of CD as a stroke risk factor. A logistic regression model was developed to identify social variables that could predict the risk of CD stroke. The diagnosis of CD was established after stroke in 42.5% of CD stroke patients. Most respondents (95%) were not aware of stroke risk in CD. Chagasic patients had the lowest rate of awareness about stroke risk (2.5 vs 7.1%), although they had the greatest knowledge about the kissing bug vector (83.7 vs 62.1%; p<0.001). The main social variables associated with CD stroke were: having family members with Chagas' disease (p<0.0001; odds ratio 10.1; 95% CI 3.6-16.1) and a past history of living in a mud-brick house during childhood (p<0.001; odds ratio 8.9; 95% CI: 4.1-24.6). Awareness about CD as a risk factor of stroke is low. Educational campaigns about risk of stroke in CD patients are encouraged.

Variables that modulate the spatial distribution of Trypanosoma cruzi and Trypanosoma evansi in the Brazilian Pantanal

An evaluation was made on how the landscape and cattle ranching affect the transmission cycles and the patterns of tripanosomatid infection ( Trypanosoma cruzi and Trypanosoma evansi) of small wild mammals in the Pantanal. This region comprises a large natural environment with a multiplicity of habitats, wide variety of biodiversity besides the presence of livestock. T. cruzi and T. evansi infections were evaluated by parasitological and serological methods in one preserved and one cattle ranching area. The diversity of the small mammal fauna showed to be the same in the two studied areas, however, their relative abundance was different. Distinct enzootiological scenarios of both trypanosomatids could be observed. Transmission of T. cruzi occurred mainly in forested areas, in the two study areas, while T. evansi occurred dispersed among all habitats studied in the unpreserved area. The arboreal rodent Oecomys mamorae, the most abundant species in both areas, displayed high T. cruzi and T. evansi serum prevalence and parasitemias. Also, the caviomorph rodent Thrichomys pachyurus was shown to be an important host due to its expressive relative abundance, prevalence of infection by both trypanosomatid species and a broad range use of habitats. The role of the small mammal fauna in the transmission cycle of both trypanosomes species seems to be distinct according to land use since we found a broad range of T. evansi infected hosts in the preserved area in contrast to cattle ranching area and a half number of the rodents species infected with T. cruzi in unpreserved in comparison to protect area. The present study showed that cattle ranching in this study area did not enhance overall prevalence of T. cruzi infection among small wild mammals. Together with the observation that small mammals diversity in FA is similar to RN area suggest that ranching activity may also not necessarily conduct to biodiversity loss or risk of Chagas disease.

DDT is back: let us spray!

DDT is back: let us spray!

Lessons from a national survey of Chagas disease transmission risk in Colombia

In recent years, there has been a revitalization of large-scale programmes to control parasitic disease in developing countries. In 1997, the Governments of Colombia, Venezuela, Ecuador and Peru committed themselves to replicate the cost-effective elimination of Trypanosoma cruzi transmission achieved in the Southern Cone by using insecticides against the domestic triatomine vectors (in combination with blood-bank screening). Central American Governments launched a complementary initiative. All plan to interrupt vectorial transmission throughout the region by 2010 but specific targets are decided nationally. In this article, we highlight the novel approach taken by the Colombian Government for determining the geographic distribution of Chagas disease risk to select where to intervene first.

Ecologic niche modeling and potential reservoirs for Chagas disease, Mexico.

Ecologic niche modeling may improve our understanding of epidemiologically relevant vector and parasite-reservoir distributions. We used this tool to identify host relationships of Triatoma species implicated in transmission of Chagas disease. Associations have been documented between the protracta complex (Triatoma: Triatominae: Reduviidae) with packrat species (Neotoma spp.), providing an excellent case study for the broader challenge of developing hypotheses of association. Species pairs that were identified coincided exactly with those in previous studies, suggesting that local interactions between Triatoma and Neotoma species and subspecies have implications at a geographic level. Nothing is known about sylvatic associates of T. barberi, which are considered the primary Chagas vector in Mexico; its geographic distribution coincided closely with that of N. mexicana, suggesting interaction. The presence of the species was confirmed in two regions where it had been predicted but not previously collected. This approach may help in identifying Chagas disease risk areas, planning vector-control strategies, and exploring parasite-reservoir associations for other emerging diseases.

Chagas disease in the Brazilian Amazon: IV. a new cross-sectional study.

A new conglomerate family sample of 194 dwellings with 996 resident persons were studied in the town of Barcelos, State of Amazonas, in order to re-evaluate the risk of Chagas disease. During the survey the persons were interviewed and in this occasion we showed to them a collection of Panstrongylus, Rhodnius and Triatoma, asking if they recognized and eventually have been bitten by this kind of bugs. At this time we collected 500 ul of blood in microtainer tubes from 886 interviewed persons who gave permission after informed consent. A screening test for T. cruzi antibodies based on agglutination of colored polymer particles, sensitized with three different synthetic peptides of T. cruzi (ID-PaGIA Chagas Test), showed 13.2% of sera positivity, but only 6.8% were confirmed by indirect immunofluorescence, and ELISA with purified T. cruzi antigens. Two hundred and six interviewed persons (20.7%) recognized the triatomines, as "piaçavas' lice" and 62 (30%) confirmed that have been bitten by the bugs, 25.8% of them had a positive serology for T. cruzi infection. Electrocardiographic alterations were shown in 9.3% of the seropositives and in 11.9% of the seronegative cases. This was considered not statistically significant.