The Hidden Hand of Asymptomatic Infection Hinders Control of Neglected Tropical Diseases: A Modeling Analysis.

BACKGROUND: Neglected tropical diseases are responsible for considerable morbidity and mortality in low-income populations. International efforts have reduced their global burden, but transmission is persistent and case-finding-based interventions rarely target asymptomatic individuals. METHODS: We develop a generic mathematical modeling framework for analyzing the dynamics of visceral leishmaniasis in the Indian sub-continent (VL), gambiense sleeping sickness (gHAT), and Chagas disease and use it to assess the possible contribution of asymptomatics who later develop disease (pre-symptomatics) and those who do not (non-symptomatics) to the maintenance of infection. Plausible interventions, including active screening, vector control, and reduced time to detection, are simulated for the three diseases. RESULTS: We found that the high asymptomatic contribution to transmission for Chagas and gHAT and the apparently high basic reproductive number of VL may undermine long-term control. However, the ability to treat some asymptomatics for Chagas and gHAT should make them more controllable, albeit over relatively long time periods due to the slow dynamics of these diseases. For VL, the toxicity of available therapeutics means the asymptomatic population cannot currently be treated, but combining treatment of symptomatics and vector control could yield a quick reduction in transmission. CONCLUSIONS: Despite the uncertainty in natural history, it appears there is already a relatively good toolbox of interventions to eliminate gHAT, and it is likely that Chagas will need improvements to diagnostics and their use to better target pre-symptomatics. The situation for VL is less clear, and model predictions could be improved by additional empirical data. However, interventions may have to improve to successfully eliminate this disease.

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

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

The Development of a One-Step RT-qPCR for the Detection and Quantification of Viable Forms of Trypanosoma cruzi in Açai Samples from Areas at Risk of Chagas Disease through Oral Transmission.

Currently, approximately 70% of new cases of Chagas disease (CD) in Brazil are attributed to oral transmission, particularly through foods such as açaí, bacaba, and sugarcane juice, primarily in the northern and northeastern regions of the country. This underscores the imperative need to control the spread of the disease. The methods utilized to conduct quality control for food associated with outbreaks and to assess the potential for the oral transmission of CD through consuming açaí primarily rely on isolating the parasite or inoculating food into experimental animals, restricting the analyses to major research centers. While there are existing studies in the literature on the detection and quantification of T. cruzi DNA in açaí, the evaluation of parasites' viability using molecular methods in this type of sample and differentiating between live and dead parasites in açaí pulp remain challenging. Consequently, we developed a molecular methodology based on RT-qPCR for detecting and quantifying viable T. cruzi in açaí pulp samples. This protocol enables the stabilization and preservation of nucleic acids in açaí, along with incorporating an exogenous internal amplification control. The standardization of the RNA extraction method involved a simple and reproducible approach, coupled with a one-step RT-qPCR assay. The assay underwent validation with various T. cruzi DTUs and demonstrated sensitivity in detecting up to 0.1 viable parasite equivalents/mL in açaí samples. Furthermore, we investigated the effectiveness of a bleaching method in eliminating viable parasites in açaí samples contaminated with T. cruzi by comparing the detection of DNA versus RNA. Finally, we validated this methodology using açaí pulp samples positive for T. cruzi DNA, which were collected in a municipality with a history of oral CD outbreaks (Coari-AM). This validation involved comparing the detection and quantification of total versus viable T. cruzi. Collectively, our findings demonstrate the feasibility of this methodology in detecting viable forms of T. cruzi in açaí pulp samples, emerging as a crucial tool for monitoring oral outbreaks of Chagas disease resulting from açaí consumption.

Transovarial transmission of a core virome in the Chagas disease vector Rhodnius prolixus.

Triatomine assassin bugs comprise hematophagous insect vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Although the microbiome of these species has been investigated to some extent, only one virus infecting Triatoma infestans has been identified to date. Here, we describe for the first time seven (+) single-strand RNA viruses (RpV1-7) infecting Rhodnius prolixus, a primary vector of Chagas disease in Central and South America. We show that the RpVs belong to the Iflaviridae, Permutotetraviridae and Solemoviridae and are vertically transmitted from the mothers to the progeny via transovarial transmission. Consistent with this, all the RpVs, except RpV2 that is related to the entomopathogenic Slow bee paralysis virus, established persistent infections in our R. prolixus colony. Furthermore, we show that R. prolixus ovaries express 22-nucleotide viral siRNAs (vsiRNAs), but not viral piRNAs, that originate from the processing of dsRNA intermediates during viral replication of the RpVs. Interestingly, the permutotetraviruses and sobemoviruses display shared pools of vsiRNAs that might provide the basis for a cross-immunity system. The vsiRNAs are maternally deposited in the eggs, where they likely contribute to reduce the viral load and protect the developing embryos. Our results unveil for the first time a complex core virome in R. prolixus and begin to shed light on the RNAi-based antiviral defenses in triatomines.

Experimental infection of Rhodnius robustus Larrousse, 1927 (Hemiptera, Reduviidae, Triatominae) with Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida, Trypanosomatidae) IV.

Vector competence of triatomines (kissing bugs) for Trypanosoma cruzi transmission depends on the parasite-vector interaction and the genetic constitution of both. This study evaluates the susceptibility and vector competence of Rhodnius robustus experimentally infected with T. cruzi IV (TcIV). Nymphs were fed on infected mice or an artificial feeder with blood containing culture-derived metacyclic trypomastigotes (CMT) or blood trypomastigotes (BT). The intestinal contents (IC) and excreta of the insects were examined by fresh examination and kDNA-PCR. The rate of metacyclogenesis was also determined by differential counts. Fifth instar nymphs fed with CMT ingested a greater blood volume (mean of 74.5 µL) and a greater amount of parasites (mean of 149,000 CMT/µL), and had higher positivity in the fresh examination of the IC. Third instar nymphs fed with CMT had higher positivity (33.3%) in the fresh examination of the excreta. On the 20th day after infection (dai), infective metacyclic trypomastigote (MT) forms were predominant in the excreta of 3/4 experimental groups, and on the 30th dai, the different parasitic forms were observed in the IC of all the groups. Higher percentages of MT were observed in the excreta of the 5th instar nymphs group (84.1%) and in the IC of the 3rd instar nymphs group (80.0%). Rhodnius robustus presented high susceptibility to infection since all nymphs were infected, regardless of the method used for blood meal, in addition these insects demonstrated vector competence for TcIV with high rates of metacyclogenesis being evident.

Circulating Cytokine and Chemokine Profiles of Trypanosoma cruzi-Infected Women During Pregnancy and Its Association With Congenital Transmission.

BACKGROUND: Trypanosoma cruzi, the causative agent of Chagas disease, can be transmitted to the offspring of infected women, which constitutes an epidemiologically significant parasite transmission route in nonendemic areas. It is relevant to evaluate differentially expressed factors in T. cruzi-infected pregnant women as potential markers of Chagas congenital transmission. METHODS: Circulating levels of 12 cytokines and chemokines were measured by enzyme-linked immunosorbent assay or cytometric bead array in T. cruzi-infected and uninfected pregnant women in their second trimester of pregnancy and control groups of T. cruzi-infected and uninfected nonpregnant women. RESULTS: Trypanosoma cruzi-infected women showed a proinflammatory Th1-biased profile, with increased levels of tumor necrosis factor (TNF)-α, interleukin (IL)-12p70, IL-15, and monokine induced by interferon-gamma (MIG). Uninfected pregnant women presented a biased response towards Th2/Th17/Treg profiles, with increased plasma levels of IL-5, IL-6, IL-1ß, IL-17A, and IL-10. Finally, we identified that high parasitemia together with low levels of TNF-α, IL-15, and IL-17, low TNF-α/IL-10 ratio, and high IL-12p70 levels are factors associated with an increased probability of Chagas congenital transmission. CONCLUSIONS: Trypanosoma cruzi-infected pregnant women who did not transmit the infection to their babies exhibited a distinct proinflammatory cytokine profile that might serve as a potential predictive marker of congenital transmission.

Systematic review on the biology, ecology, genetic diversity and parasite transmission potential of Panstrongylus geniculatus (Latreille 1811) in Latin America.

Panstrongylus geniculatus (Latreille, 1811) is the triatomine with the largest geographic distribution in Latin America. It has been reported in 18 countries from southern Mexico to northern Argentina, including the Caribbean islands. Although most reports indicate that P. geniculatus has wild habitats, this species has intrusive habits regarding human dwellings mainly located in intermediate deforested areas. It is attracted by artificial light from urban and rural buildings, raising the risk of transmission of Trypanosoma cruzi. Despite the wide body of published information on P. geniculatus, many knowledge gaps exist about its biology and epidemiological potential. For this reason, we analysed the literature for P. geniculatus in Scopus, PubMed, Scielo, Google Scholar and the BibTriv3.0 databases to update existing knowledge and provide better information on its geographic distribution, life cycle, genetic diversity, evidence of intrusion and domiciliation, vector-related circulating discrete taxonomic units, possible role in oral T. cruzi transmission, and the effect of climate change on its biology and epidemiology.

Biology of Chagas disease vectors: biological cycle and emergence rates of Rhodnius marabaensis Souza et al., 2016 (Hemiptera, Reduviidae, Triatominae) under laboratory conditions.

In Latin America, Chagas disease has been mostly transmitted to humans by contact with the feces or urine of triatomine species infected with the protozoan Trypanosoma cruzi. There are currently 156 species in the subfamily Triatominae, distributed in 18 genera and five tribes. The prolixus group of the genus Rhodnius is composed of 11 species. Rhodnius marabaensis was the last species described and considered in this grouping of vectors. Knowledge about the biology, ecology, and behavior of these vectors is of great epidemiological importance, and in order to expand the knowledge of the biology of R. marabaensis, this paper describes the biological cycle and emergence rates of the species under laboratory conditions. The experiment was carried out at temperatures ranging from 15.5 to 29 °C (average of 24 °C) and humidity ranging from 51.4 to 72.2 (average of 63). For each of the fifteen couples, the egg emergence rate was calculated throughout the oviposition period. The oviposition period lasted from February to September, and the emergence rate varied between 13.9 and 53.3%. R. marabaensis presented an emergence rate of 46.7% and a total biological cycle of 193 days (the mean time required for emergence (25.1 days), 1st nymphal instar (19.4 days), 2nd nymphal instar (22.1 days), 3rd nymphal instar (26.2 days), 4th nymphal instar (29.3 days), and 5th nymphal instar (70.9 days)). Based on the biological cycle of R. marabaensis and 14 other Rhodnius species already described in the literature, it was also possible to calculate the averages for the groups prolixus, pictipes, and pallescens and, mainly, for the genus Rhodnius, contributing to the knowledge of this important group of Chagas disease vectors.

Satellitome Analysis of Rhodnius prolixus, One of the Main Chagas Disease Vector Species.

The triatomine Rhodnius prolixus is the main vector of Chagas disease in countries such as Colombia and Venezuela, and the first kissing bug whose genome has been sequenced and assembled. In the repetitive genome fraction (repeatome) of this species, the transposable elements represented 19% of R. prolixus genome, being mostly DNA transposon (Class II elements). However, scarce information has been published regarding another important repeated DNA fraction, the satellite DNA (satDNA), or satellitome. Here, we offer, for the first time, extended data about satellite DNA families in the R. prolixus genome using bioinformatics pipeline based on low-coverage sequencing data. The satellitome of R. prolixus represents 8% of the total genome and it is composed by 39 satDNA families, including four satDNA families that are shared with Triatoma infestans, as well as telomeric (TTAGG)n and (GATA)n repeats, also present in the T. infestans genome. Only three of them exceed 1% of the genome. Chromosomal hybridization with these satDNA probes showed dispersed signals over the euchromatin of all chromosomes, both in autosomes and sex chromosomes. Moreover, clustering analysis revealed that most abundant satDNA families configured several superclusters, indicating that R. prolixus satellitome is complex and that the four most abundant satDNA families are composed by different subfamilies. Additionally, transcription of satDNA families was analyzed in different tissues, showing that 33 out of 39 satDNA families are transcribed in four different patterns of expression across samples.

An Overview on Target-Based Drug Design against Kinetoplastid Protozoan Infections: Human African Trypanosomiasis, Chagas Disease and Leishmaniases.

The protozoan diseases Human African Trypanosomiasis (HAT), Chagas disease (CD), and leishmaniases span worldwide and therefore their impact is a universal concern. The present regimen against kinetoplastid protozoan infections is poor and insufficient. Target-based design expands the horizon of drug design and development and offers novel chemical entities and potential drug candidates to the therapeutic arsenal against the aforementioned neglected diseases. In this review, we report the most promising targets of the main kinetoplastid parasites, as well as their corresponding inhibitors. This overview is part of the Special Issue, entitled "Advances of Medicinal Chemistry against Kinetoplastid Protozoa (Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp.) Infections: Drug Design, Synthesis and Pharmacology".

Chagas Disease in the United States: a Public Health Approach.

Trypanosoma cruzi is the etiological agent of Chagas disease, usually transmitted by triatomine vectors. An estimated 20 to 30% of infected individuals develop potentially lethal cardiac or gastrointestinal disease. Sylvatic transmission cycles exist in the southern United States, involving 11 triatomine vector species and infected mammals such as rodents, opossums, and dogs. Nevertheless, imported chronic T. cruzi infections in migrants from Latin America vastly outnumber locally acquired human cases. Benznidazole is now FDA approved, and clinical and public health efforts are under way by researchers and health departments in a number of states. Making progress will require efforts to improve awareness among providers and patients, data on diagnostic test performance and expanded availability of confirmatory testing, and evidence-based strategies to improve access to appropriate management of Chagas disease in the United States.

Prevalence, infected density or individual probability of infection? Assessing vector infection risk in the wild transmission of Chagas disease.

Vector-borne infectious disease dynamics result mainly from the intertwined effect of the diversity, abundance, and behaviour of hosts and vectors. Most studies, however, have analysed the relationship between host-species diversity and infection risk, focusing on vector population instead of individuals, probably dismissing the level at which the transmission process occurs. In this paper, we examine the importance of the host community in accounting for infection risk, at both population and individual levels, using the wild transmission of the protozoan that causes Chagas disease as a vector-borne disease model. Chagas disease is caused by Trypanosoma cruzi, transmitted by triatomine insects to mammals. We assessed if T. cruzi infection in vectors is explained by small mammal diversity and their densities (total and infected), when infection risk is measured at population level as infection prevalence (under a frequency-dependent transmission approach) and as density of infected vectors (density-dependent transmission approach), and when measured at individual level as vector infection probability. We analysed the infection status of 1974 vectors and co-occurring small mammal hosts in a semiarid-Mediterranean ecosystem. Results revealed that regardless of the level of analysis, only one host rodent species accounted for most variation in vector infection risk, suggesting a key role in the transmission cycle. To determine the factors explaining vector-borne disease dynamics, infection risk should be assessed at different scales, reflecting the factors meaningful from the vector's perspective and considering vector class-specific features.

Epidemiology of Chagas disease in pregnant women and congenital transmission of Trypanosoma cruzi in the Americas: systematic review and meta-analysis.

OBJECTIVE: To estimate the prevalence of Chagas disease in pregnant women and the vertical transmission of the disease. METHODS: Observational studies were identified from eight electronic databases, and details on study design, population and prevalence of Chagas disease were extracted. The data were pooled using a random-effects model, and choropleth maps were created based on geopolitical regions and countries. RESULTS: The search identified 7788 articles, of which 50 were eligible. We observed a 9% prevalence of Chagas disease among pregnant women in the Americas (95% confidence interval [CI]: 8-10, I2  = 99.96%). High disease prevalence was identified in pregnant women in South American countries (12%, 95% CI: 11-13), while lower values were identified in pregnant women in North America (2%, 95% CI: 1-3). Countries with medium Human Development Index (HDI) had a higher prevalence of Chagas disease in pregnant women (15%, 95% CI: 13-16, I2  = 99.98%) than countries with high HDI (3%, 95% CI: 2-3). The rate of vertical transmission in the continent was 2% (95% CI: 1-2). The statistical analysis showed that this heterogeneity was explained by the study design, region of the Americas and mean income of the country. CONCLUSION: South and Central American countries have a high prevalence and vertical transmission of Chagas disease. Therefore, systematic screens for this disease during the prenatal period are necessary in addition to the diagnosis and treatment of children at risk for Trypanosoma cruzi infection.

OBJECTIF: Estimer la prévalence de la maladie de Chagas chez les femmes enceintes et la transmission verticale de la maladie. MÉTHODES: Des études d'observation ont été identifiées à partir de huit bases de données électroniques et des détails sur la concept de l'étude, la population et la prévalence de la maladie de Chagas ont été extraits. Les données ont été regroupées à l'aide d'un modèle à effets aléatoires et des cartes choroplèthes ont été créées en fonction des régions et des pays géopolitiques. RÉSULTATS: La recherche a identifié 7.788 articles, dont 50 étaient éligibles. Nous avons observé une prévalence de 9% de la maladie de Chagas chez les femmes enceintes dans les Amériques (intervalle de confiance [IC] à 95%: 8-10, I2 = 99,96%). Une prévalence élevée de la maladie a été identifiée chez les femmes enceintes dans les pays d'Amérique du Sud (12%, IC95%: 11-13), tandis que des valeurs plus faibles ont été identifiées chez les femmes enceintes d'Amérique du Nord (2%, IC95%: 1-3). Les pays à indice de développement humain (IDH) moyen présentaient une prévalence plus élevée de la maladie de Chagas chez les femmes enceintes (15%, IC95%: 13-16, I2 = 99,98%) que les pays à IDH élevé (3%, IC95%: 2 -3). Le taux de transmission verticale sur le continent était de 2% (IC95%: 1-2). L'analyse statistique a montré que cette hétérogénéité s'expliquait par le concept d'étude, la région des Amériques et le revenu moyen du pays. CONCLUSION: Les pays d'Amérique du Sud et d'Amérique centrale ont une prévalence élevée et de transmission verticale de la maladie de Chagas. Par conséquent, des dépistages systématiques de cette maladie pendant la période prénatale sont nécessaires en plus du diagnostic et du traitement des enfants à risque d'infection par Trypanosoma cruzi.

Autochthonous Chagas Disease - Missouri, 2018.

On December 13, 2017, the Missouri Department of Health and Senior Services (MDHSS) was notified of a suspected case of Chagas disease in a Missouri woman. The patient had donated blood, and laboratory screening revealed antibodies to Trypanosoma cruzi, the parasite that causes Chagas disease. Evaluation by physicians found no clinical symptoms consistent with Chagas disease. The patient had no travel history that would have suggested a significant risk for Chagas disease risk and had no occupational exposure to the disease agent. She had never received a blood transfusion or organ transplant. Confirmatory testing of the patient's serum at CDC for T. cruzi antibody was consistent with infection. These findings raise the possibility that the exposure to T. cruzi occurred locally (autochthonously) in Missouri. Although the insect vector for the parasite T. cruzi, triatomines (commonly known as "kissing bugs"), has been identified previously in Missouri, no locally acquired human cases of Chagas disease have been identified in the state. Health care providers and public health professionals should be aware of the possibility of locally acquired Chagas disease in the southern United States.

Decoys and Dilution: The Impact of Incompetent Hosts on Prevalence of Chagas Disease.

Biodiversity is commonly believed to reduce risk of vector-borne zoonoses. However, researchers already showed that the effect of biodiversity on disease transmission is not that straightforward. This study focuses on the effect of biodiversity, specifically on the effect of the decoy process (additional hosts distracting vectors from their focal host), on reducing infections of vector-borne diseases in humans. Here, we consider the specific case of Chagas disease and use mathematical population models to observe the impact on human infection of the proximity of chickens, which are incompetent hosts for the parasite but serve as a preferred food source for vectors. We consider three cases as the distance between the two host populations varies: short (when farmers bring chickens inside the home to protect them from predators), intermediate (close enough for vectors with one host to detect the presence of the other host type), and far (separate enclosed buildings such as a home and hen-house). Our analysis shows that the presence of chickens reduces parasite prevalence in humans only at an intermediate distance under the condition that the vector birth rate from feeding on chickens is sufficiently low.

Pattern of climate connectivity and equivalent niche of Triatominae species of the Phyllosoma complex.

The Phyllosoma complex is a Triatominae (Hemiptera: Reduviidae) group of medical importance involved in Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) transmission. Most of the members of this group are endemic and sympatric species with distribution in Mexico and the southern U.S.A. We employed MaxEnt to construct ecological niche models of nine species of Triatominae to test three hypothesis: (a) whether species with a broad climatic niche breadth occupy a broader geographical range than species with a narrow climatic breadth, (b) whether species with broad distribution present high degree of climatic fragmentation/isolation, which was tested through landscape metrics; and (c) whether the species share the same climatic niche space (niche conservatism) considered through an equivalence test implemented in ENMtools. Overall, our results suggest that the geographical distribution of this complex is influenced mainly by temperature seasonality where all suitable areas are places of current and potential transmission of T. cruzi. Niche breadth in the Phyllosoma complex is associated with the geographical distribution range, and the geographical range affects the climatic connectivity. We found no strong evidence of niche climatic divergence in members of this complex. We discuss the epidemiological implications of these results.

Domestic host availability modifies human-triatomine contact and host shifts of the Chagas disease vector Triatoma infestans in the humid Argentine Chaco.

Domestic animals may affect human-vector contact and parasite transmission rates. We investigated the relationships between host-feeding choices, site-specific host availability, bug nutritional status, stage and abundance of Triatoma infestans Klug (Heteroptera: Reduviidae) in rural houses of Pampa del Indio during spring. We identified the bloodmeal sources of 865 triatomines collected in 70 sites from four main ecotopes. The main sources in domiciles were human (65.9%), chicken (23.4%) and dog (22.4%); dog (64.4%, 35.3%) and chicken (33.1%, 75.4%) in kitchens and storerooms, respectively; and chicken (94.7%) in chicken coops. Using random-intercept logistic regression clustered by domicile, the fraction of human-fed triatomines strongly decreased with increasing proportions of chicken- and dog-fed bugs, dropping from 96.4% when no chicken or dog slept indoors at night to 59.4% when both did. The fraction of dog-fed bugs significantly decreased with increasing human and chicken blood indices, and marginally increased with an indoor-resting dog. Mixed blood meals occurred 3.62 times more often when a chicken or a dog slept indoors. Host blood source did not affect mean body weight adjusted for body length and bug stage. Indoor-resting chickens and dogs greatly modified human-bug contact rates, and may be targeted with long-lasting systemic insecticides to suppress infestation.

Effects of the infection with Trypanosoma cruzi on the feeding and excretion/defecation patterns of Triatoma infestans.

Transmission of Trypanosma cruzi (Kinetoplastida: Trypanosomatidae) occurs when feces/urine of infected triatomines come into contact with mucous membranes or damaged skin, and this occurs mainly when insects defecate while feeding on the host. Thus, the vector competence of the triatomines is associated with their feeding and excretion/defecation behavior. This work studied for the first time the effect of T. cruzi infection on feeding and excretion/defecation patterns of Triatoma infestans (Hemiptera: Reduviidae). Uninfected and infected fifth-instar nymphs were fed ad libitum and their feeding behavior and defecations were registered during and after feeding. The feeding pattern did not show differences between the experimental groups. However, the infected nymphs began to defecate earlier, defecated in greater quantity and there was a greater proportion of defecating individuals compared to uninfected nymphs. These results show that T. cruzi affected the excretion/defecation pattern of T. infestans in a way that would increase the probability of contact between infective feces and the mammalian host.

Infestation dynamics of Triatoma dimidiata in highly deforested tropical dry forest regions of Guatemala.

BACKGROUND: Deforestation, driven by anthropogenic change in land use, influences the behaviour and abundance of vector-borne diseases. For various species of Chagas disease vectors, there is evidence that change in land use affects population density and abundance. Triatoma dimidiata is the most important Chagas vector in Guatemala, and at least one million people live in T. dimidiata endemic areas; however, infestation dynamics vary among regions, from high infestation with all life stages to low seasonal infestation by sylvatic adults. OBJECTIVES: The aim of this study was to evaluate how land-use, combined with domiciliary risk factors, influences the infestation dynamics of T. dimidiata for four villages in a dry forest region with a strong deforestation history. METHODS: Land use, measured with drone and satellite images, was classified into four categories (houses, monocultures and pastures, woodland and shrubland, and bare soil). Domiciliary risk factors and infestation were assessed through entomological surveys. Statistical analyses compared infestation indices and the ability of land use and domiciliary risk factors to explain infestation. FINDINGS: Two villages had significantly higher infestation (26 and 30% vs. 5 and 6%), yet all villages had high colonisation (71-100% of infested houses had immature insects), with no significant difference among them. Because of the high level of deforestation across the study area, land use was not related to infestation; however, domiciliary risk factors were. A model based on four weighted domiciliary risk factors (adobe or bajareque walls, intradomicile animals, intradomicile clutter, and dirt floors) explains the infestation risk. MAIN CONCLUSIONS: Because almost all infested houses have reproducing populations in this deforested dry forest region and statistical analysis identified the domiciliary risk factors for infestation, intermediate and long-term control of Chagas disease vectors in this region requires management of these risk factors.

Human acute Chagas disease: changes in factor VII, activated protein C and hepatic enzymes from patients of oral outbreaks in Pará State (Brazilian Amazon).

Oral transmission of Chagas disease has been increasing in Latin American countries. The present study aimed to investigate changes in hepatic function, coagulation factor levels and parasite load in human acute Chagas disease (ACD) secondary to oral Trypanosoma cruzi transmission. Clinical and epidemiological findings of 102 infected individuals attended in the State of Pará from October 2013 to February 2016 were included. The most common symptoms were fever (98%), asthenia (83.3%), face and limb edema (80.4%), headache (74.5%) and myalgia (72.5%). The hepatic enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) of 30 ACD patients were higher compared with controls, and this increase was independent of the treatment with benznidazole. Moreover, ACD individuals had higher plasma levels of activated protein C and lower levels of factor VII of the coagulation cascade. Patients with the highest parasite load had also the most increased transaminase levels. Also, ALT and AST were associated moderately (r = 0.429) and strongly (r = 0.595) with parasite load respectively. In conclusion, the present study raises the possibility that a disturbance in coagulation and hepatic function may be linked to human ACD.