Comparative study of the stridulatory groove in species of Triatoma (Hemiptera: Reduviidae) from Mexico.

The stridulation in the subfamily Triatominae has been identified as a means of communication between species, produced by the friction of the proboscis on the prosternal stridulatory groove. Despite its biological significance, this phenomenon remains understudied, with the signal's production seemingly contingent upon the morphology of the stridulatory groove. In this study, we examined the morphology of stridulatory grooves in females and males of five species and two subspecies of Mexican triatomines using morphometric and scanning electron microscopical analysis. Our findings reveal that all analyzed species exhibit triangular-shaped stridulatory grooves with parallel ridges covering the entire groove, bordered on each side, and covered with setae. Surprisingly, we observed noticeable differences in the number of ridges and inter-ridge distance between the species Triatoma lecticularia and Triatoma rubida (p < 0.001 and p < 0.009, respectively), indicating sexual dimorphism in this aspect, a phenomenon not previously reported in the morphology of this structure. Our findings shed light on the intricate morphology of the stridulatory groove in Mexican triatomines, suggesting potential implications for their behavior and intra-specific communication.

Reproductive consequences of the interaction Trypanosoma cruzi - Triatoma infestans and its trade-off with survival.

Relative little is known about fitness effects and life history trade-off of Trypanosoma cruzi in Triatoma infestans, the main vector of Chagas disease in Argentina. Previous studies revealed some costs related to development, excretion, and toxicology or their possible trade-offs, but none address effects on reproduction. To study the effect of T. cruzi infection on reproductive efficiency and survival of T. infestans we set up four treatments: both genders uninfected, both genders infected, female infected - males uninfected and female uninfected - males infected. The infection was induced during the third, fourth, and fifth nymphal instars. Reproductive efficiency and longevity variables were recorded. Our results showed that the infection by T. cruzi increased reproductive efficiency and reduced survival of T. infestans. Pairs where one or both individuals were infected presented a greater percentage copulation, of egg-laying females, the onset of copulation and oviposition occurred earlier, and age-specific fecundity was notably higher. Regarding fertility, infected females displayed higher rates irrespective of the infective status of the male counterpart. A reduction in longevity was observed in infected males and females. These findings highlighted that the infection significantly alters the trade-off reproductive efficiency-survival of T. infestans, with the impact differing according to the infection status of each gender, suggesting a complex interplay rather than a simple additive effect. This response corresponds to the reproductive compensation hypothesis.

Life history data of four populations of Triatoma mexicana (Hemiptera: Reduviidae) from Central Mexico.

Triatomine bugs are vectors for the Trypanosoma cruzi Chagas parasites, the etiological agent for Chagas disease. This study evaluated 6 epidemiologically significant behaviors (development time, number of blood meals required for molting to the next instar, mortality rate, aggressiveness, feeding duration, and defecation delay) across 4 populations of Triatoma mexicana Herrich-Schaeffer (Heteroptera: Reduviidae), a major T. cruzi vector in Central Mexico. We collected triatomines from areas characterized by high (HP), medium (MP), medium-high (MHP), and low (LP) prevalence of human T. cruzi infection. The MHP population had the shortest development time, <290 days. Both the HP and MP populations required the most blood meals to molt to the next instar, with a median of 13. Mortality rates varied across all populations, ranging from 44% to 52%. All of the tested populations showed aggressive behavior during feeding. All populations shared similar feeding durations, with most exceeding 13 min and increasing with each instar. Quick defecation, during feeding, immediately after or less than 1 min after feeding, was observed in most nymphs (78%-90%) from the MP and MHP populations and adults (74%-92%) from HP, MP, and MHP populations. Though most parameters suggest a low potential for T. mexicana to transmit T. cruzi, unique feeding and defecation behaviors in 3 populations (excluding the LP group) could elevate their epidemiological importance. These population-specific differences may contribute to the varying prevalence rates of T. cruzi infection in areas where T. mexicana is found.

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

BACKGROUND: The 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. METHODS: We 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. RESULTS: The 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. CONCLUSIONS: Triatoma 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.

Presence of Triatoma breyeri (Reduviidae, Triatominae) in Bolivia.

The study focuses on identifying and understanding the ecological dynamics of Triatoma breyeri in Bolivia. Morphological identification and molecular analysis using gene fragments (COI, CytB and 16S) confirms T. breyeri's presence and its relation to other species. The species has been consistently found in the Estancia-Mataral-La Palma region since 2010 but has not spread to other regions in Bolivia. The region of occurrence is a small characteristic dry inter-Andean valley. A MaxEnt model suggests part of the Bolivian Montane Dry Forest ecoregion serves as a unique habitat within its range. The infrequent presence in Bolivia and the distance from its main range in Argentina suggest recent accidental introduction, possibly through human transport. Further research is needed to comprehend its persistence in this small area of Bolivia.

Variety is the spice: The role of morphological variation of Triatoma infestans (Hemiptera, Reduviidae) at a macro-scale.

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi (Chagas, 1909). One of the primary vectors of T. cruzi in South America is Triatoma infestans (Klug, 1834). This triatomine species is distributed across a huge latitudinal gradient, inhabiting domiciliary , peridomiciliary , and wild environments. Its wide geographic distribution provides an excellent opportunity to study the relationships between environmental gradients and intraspecific morphological variation. In this study, we investigated variations in wing size and shape in T. infestans across six ecoregions. We aimed to address the following questions: How do wing size and shape vary on a regional scale, does morphological variation follow specific patterns along an environmental or latitudinal gradient, and what environmental factors might contribute to wing variation? Geometric morphometric methods were applied to the wings of 162 females belonging to 21 T. infestans populations, 13 from Argentina (n = 105), 5 from Bolivia (n = 42), and 3 from Paraguay (n = 15). A comparison of wing centroid size across the 21 populations showed significant differences. Canonical Variate Analysis (CVA) revealed significant differences in wing shape between the populations from Argentina, Bolivia, and Paraguay, although there was a considerable overlap, especially among the Argentinian populations. Well-structured populations were observed for the Bolivian and Paraguayan groups. Two analyses were performed to assess the association between wing size and shape, geographic and climatic variables: multiple linear regression analysis (MRA) for size and Partial Least Squares (PLS) regression for shape. The MRA showed a significant general model fit. Six temperature-related variables, one precipitation-related variable, and the latitude showed significant associations with wing size. The PLS analysis revealed a significant correlation between wing shape with latitude, longitude, temperature-related, and rainfall-related variables. Wing size and shape in T. infestans populations varied across geographic distribution. Our findings demonstrate that geographic and climatic variables significantly influence T. infestans wing morphology.

Domestic (re)infestation risk with the main vector Triatoma infestans increases with surrounding green vegetation and social vulnerability in the Argentine Chaco.

BACKGROUND: Chagas disease, caused by Trypanosoma cruzi, is still a public health problem in Latin America and in the Southern Cone countries, where Triatoma infestans is the main vector. We evaluated the relationships among the density of green vegetation around rural houses, sociodemographic characteristics, and domestic (re)infestation with T. infestans while accounting for their spatial dependence in the municipality of Pampa del Indio between 2007 and 2016. METHODS: The study comprised sociodemographic and ecological variables from 734 rural houses with no missing data. Green vegetation density surrounding houses was estimated by the normalized difference vegetation index (NDVI). We used a hierarchical Bayesian logistic regression composed of fixed effects and spatial random effects to estimate domestic infestation risk and quantile regressions to evaluate the association between surrounding NDVI and selected sociodemographic variables. RESULTS: Qom ethnicity and the number of poultry were negatively associated with surrounding NDVI, whereas overcrowding was positively associated with surrounding NDVI. Hierarchical Bayesian models identified that domestic infestation was positively associated with surrounding NDVI, suitable walls for triatomines, and overcrowding over both intervention periods. Preintervention domestic infestation also was positively associated with Qom ethnicity. Models with spatial random effects performed better than models without spatial effects. The former identified geographic areas with a domestic infestation risk not accounted for by fixed-effect variables. CONCLUSIONS: Domestic infestation with T. infestans was associated with the density of green vegetation surrounding rural houses and social vulnerability over a decade of sustained vector control interventions. High density of green vegetation surrounding rural houses was associated with households with more vulnerable social conditions. Evaluation of domestic infestation risk should simultaneously consider social, landscape and spatial effects to control for their mutual dependency. Hierarchical Bayesian models provided a proficient methodology to identify areas for targeted triatomine and disease surveillance and control.

Behavioral and biological parameters of six populations of Triatoma pallidipennis (Heteroptera: Reduviidae) from areas with high and low prevalence rates of Trypanosoma cruzi human infection.

In Mexico, more than 30 species of triatomines, vectors of Trypanosoma cruzi, the etiological agent of Chagas disease, have been collected. Among them, Triatoma pallidipennis stands out for its wide geographical distribution, high infection rates and domiciliation. Local populations of triatomines have shown notable biological and behavioral differences, influencing their vectorial capacity. Six behaviors of epidemiological importance, namely, egg-to-adult development time, median number of blood meals to molt to the next instar, instar mortality rates, aggressiveness (delay in initiating a meal), feeding time and defecation delay, were evaluated in this study for six populations of T. pallidipennis. Those populations from central, western and southern Mexico were arranged by pairs with a combination of high (HP) and medium (MP) of Trypanosoma cruzi human infection and most (MFC) and low (CLF) collection frequencies: HP/MFC, HP/CLF, and MP/MFC. The development time was longer in HP/CLF populations (> 220 days). The median number of blood meals to molt was similar (7-9) among five of the six populations. Mortality rates were greater (> 40 %) in HP/CLF and one MP/MFC populations. All studied populations were aggressive but exhibited slight differences among them. The feeding times were similar (≥ 10 min) for all studied populations within instars, increasing as instars progressed. An irregular pattern was observed in defecation behaviors, with marked differences even between the two populations from the same pair. High percentages of young (57.3-87.9 %), and old (62.4-89.8 %) nymphs, of female (61.1-97.3 %) and male (65.7-93.1 %) of all the studied populations defecated quickly (while eating, immediately after finishing feeding or < 1 min postfeeding). Our results indicate that the HP/MFC populations are potentially highly effective vectors for transmitting T. cruzi infections, while HP/CLF populations are potentially less effective vectors T. cruzi infections.

Morphometric study of the legs of the main Chagas vector, Triatoma infestans (Hemiptera: Reduviidae).

In triatomines, vectors of Chagas disease, active dispersal takes place by walking and flying. Flight has received more attention than walking although the last is the dispersal modality used by nymphs due to their lack of wings and also used by adults, which would facilitate the colonization and reinfestation of houses after vector control actions. The present work studied the morphometrical variation of Triatoma infestans legs, the main vector of Chagas disease the Southern Cone of South America. We described morphometric traits and the natural variation of each leg segment. Different linear, size and shape variables of each component of the three right legs of fifth instar nymphs of T. infestans were analyzed using morphometric tools. We analyzed differentiation, variation and correlation for each segment across the fore-, mid and hind legs using different statistical approaches such as general linear model, canonical variates analysis, test of equality of coefficient of variation and partial least square analysis. We also analyzed variation and correlation between segments within each leg with partial least square and morphometric disparity analyses. Our results showed that the segments differed between legs, as general trends, the dimensions (length, width and/or size) were greater in the hind legs, smaller in the forelegs and intermediate in the mid ones. The femur and tibia (length and/or width) showed differences in morphometric variation between legs and the femur and tibia showed the highest levels of correlation between legs. On the other hand, in the fore- and mid legs, the femur (length or width) showed similar variation with tibia and tarsus lengths, but in the hind legs, the femur showed similar variation with all segments and not with the tibia length, and there were strong correlations between linear measurement within each leg. Our results suggest that the femur and tibia could play a determining role in the coordination between the legs that determines the walking pattern. Considering that these segments would also be linked to the specific function that each leg has, this study suggests a preponderant role of the femur and tibia in the walking locomotion of T. infestans.

Chemical symphony: Unraveling triatomine aggregation and attraction patterns for innovative pest control solutions.

Aggregation is a spatial distribution pattern where individuals can be grouped through interaction with particular signals or cues [e.g., chemical substances]. Numerous triatomine species exhibit attraction and aggregation around both conspecific and heterospecific feces. It remains unclear whether compounds released by feces function as signals (pheromones or synomones) or cues. Employing a bioassay that mimics field conditions, we investigated the response of Triatoma pallidipennis bugs to volatiles present in its feces and blends of these compounds. Our findings indicate that short-chain aldehydes, namely nonanal, octanal, heptanal, and hexanal, attract fifth-instar nymphs. Furthermore, insects responded to individual compounds as well as secondary, ternary, and quaternary blends. The most attractive blend consisted of all four aldehydes. Additionally, quaternary blends at various compound ratios attracted fifth-instar nymphs of T. phyllosoma and T. longipennis. We discuss the potential roles of these compounds as signals or cues and explore their application as bait in control programs.

Association between environmental gradient of anthropization and phenotypic plasticity in two species of triatomines.

BACKGROUND: Triatoma garciabesi and T. guasayana are considered secondary vectors of Trypanosoma cruzi and frequently invade rural houses in central Argentina. Wing and head structures determine the ability of triatomines to disperse. Environmental changes exert selective pressures on populations of both species, promoting changes in these structures that could have consequences for flight dispersal. The aim of this study was to investigate the relationship between a gradient of anthropization and phenotypic plasticity in flight-related traits. METHODS: The research was carried out in Cruz del Eje and Ischilín departments (Córdoba, Argentina) and included 423 individuals of the two species of triatomines. To measure the degree of anthropization, a thematic map was constructed using supervised classification, from which seven landscapes were selected, and nine landscape metrics were extracted and used in a hierarchical analysis. To determine the flight capacity and the invasion of dwellings at different levels of anthropization for both species, entomological indices were calculated. Digital images of the body, head and wings were used to measure linear and geometric morphometric variables related to flight dispersion. One-way ANOVA and canonical variate analysis (CVA) were used to analyze differences in size and shape between levels of anthropization. Procrustes variance of shape was calculated to analyze differences in phenotypic variation in heads and wings. RESULTS: Hierarchical analysis was used to classify the landscapes into three levels of anthropization: high, intermediate and low. The dispersal index for both species yielded similar results across the anthropization gradient. However, in less anthropized landscapes, the density index was higher for T. garciabesi. Additionally, in highly anthropized landscapes, females and males of both species exhibited reduced numbers. Regarding phenotypic changes, the size of body, head and wings of T. garciabesi captured in the most anthropized landscapes was greater than for those captured in less anthropized landscapes. No differences in body size were observed in T. guasayana collected in the different landscapes. However, males from highly anthropized landscapes had smaller heads and wings than those captured in less anthropized landscapes. Both wing and head shapes varied between less and more anthropogenic environments in both species. CONCLUSIONS: Results of the study indicate that the flight-dispersal characteristics of T. garciabesi and T. guasayana changed in response to varying degrees of anthropization.

Influence of temperature variability on the feeding behavior and blood consumption of Triatoma infestans (Hemiptera: Reduviidae).

The transmission and incidence of vector-borne diseases rely on vector distribution and life history traits such as survival, fecundity, and feeding. Since arthropod disease vectors are ectotherms, these vital rates are strongly influenced by temperature. Chagas disease is a neglected tropical disease caused by the protozoan parasite, Trypanosoma cruzi. This parasite is transmitted when the feces of the infected triatomine enter the bloodstream of the host. One of the most important vector-species of this disease in the Southern Cone region of South America is Triatoma infestans. In this study, we evaluated the role of constant and variable environmental temperature on the feeding behavior of T. infestans. Fifth-instar nymphs were acclimatized to 4 thermal treatments comprising 2 temperatures (27 °C and 18 °C) with and without diurnal thermal variability (27 ±â€…5 °C and 18 ±â€…5 °C). Individuals were fed weekly for 7 wk to quantify their feeding. Our results showed lower feeding frequency in nymphs acclimatized to cold temperature compared to those from warmer temperature treatments. However, treatments with thermal variability presented a nonlinear effect on feeding, with an increased feeding rate in the cold, variable treatment and a decreased feeding rate in the warm, variable treatment. Individuals maintained under cold treatments, the variable temperature exhibited a higher feeding rate and the lowest amount of ingested blood among all treatments. Thus, natural diurnal temperature variation cannot be ignored if we are to make more accurate T. cruzi transmission risk predictions now and in the future.

An effective internet-based system for surveillance and elimination of triatomine insects: AlertaChirimacha.

Vector-borne diseases remain a significant public health threat in many regions of the world. Traditional vector surveillance and control methods have relied on active and passive surveillance programs, which are often costly and time-consuming. New internet-based vector surveillance systems have shown promise in removing some of the cost and labor burden from health authorities. We developed and evaluated the effectiveness of a new internet-based surveillance system, "AlertaChirimacha", for detecting Triatoma infestans (known locally by its Quechua name, Chirimacha), the Chagas disease vector, in the city of Arequipa, Peru. In the first 26 months post-implementation, AlertaChirimacha received 206 reports of residents suspecting or fearing triatomines in their homes or neighborhoods, of which we confirmed, through pictures or inspections, 11 (5.3%) to be Triatoma infestans. After microscopic examination, none of the specimens collected were infected with Trypanosoma cruzi. AlertaChirimacha received 57% more confirmed reports than the traditional surveillance system and detected 10% more infested houses than active and passive surveillance approaches combined. Through in-depth interviews we evaluate the reach, bilateral engagement, and response promptness and efficiency of AlertaChirimacha. Our study highlights the potential of internet-based vector surveillance systems, such as AlertaChirimacha, to improve vector surveillance and control efforts in resource-limited settings. This approach could decrease the cost and time horizon for the elimination of vector-mediated Chagas disease in the region.

The Pampa del Indio project: District-wide quasi-elimination of Triatoma infestans after a 9-year intervention program in the Argentine Chaco.

BACKGROUND: The elimination of Triatoma infestans, the main domestic vector of Trypanosoma cruzi, is lagging behind expectations in the Gran Chaco region. We implemented an insecticide-based intervention program and assessed its long-term effects on house infestation and bug abundance in a resource-constrained municipality (Pampa del Indio, northeastern Argentina) inhabited by creole and the Qom indigenous people (2007-2016). Key questions were whether district-wide data integration revealed patterns concealed at lower spatial levels; to what extent preintervention infestation and pyrethroid resistance challenged the effectiveness of insecticide-based control efforts, and how much control effort was needed to meet defined targets. METHODS: Supervised vector control teams i) georeferenced every housing unit at baseline (1,546); ii) evaluated house infestation using timed-manual searches with a dislodging aerosol across four rural areas designated for district-wide scaling up; iii) sprayed with pyrethroid insecticide 92.7% of all houses; iv) periodically monitored infestation and promoted householder-based surveillance, and v) selectively sprayed the infested houses, totaling 1,823 insecticide treatments throughout the program. RESULTS: Baseline house infestation (mean, 26.8%; range, 14.4-41.4%) and bug abundance plummeted over the first year postintervention (YPI). Timed searches at baseline detected 61.4-88.0% of apparent infestations revealed by any of the methods used. Housing dynamics varied widely among areas and between Qom and creole households. Preintervention triatomine abundance and the cumulative frequency of insecticide treatments were spatially aggregated in three large clusters overlapping with pyrethroid resistance, which ranged from susceptible to high. Persistent foci were suppressed with malathion. Aggregation occurred mainly at house compound or village levels. Preintervention domestic infestation and abundance were much greater in Qom than in creole households, whereas the reverse was recorded in peridomestic habitats. House infestation, rare (1.9-3.7%) over 2-6 YPI, averaged 0.66% (95% confidence interval, 0.28-1.29%) at endpoint. CONCLUSIONS: Upscale integration revealed multiple coupled heterogeneities (spatial, sociodemographic and biological) that reflect large inequalities, hamper control efforts, and provide opportunities for targeted, sustainable disease control. High-coverage, professional insecticide spraying combined with systematic surveillance-and-response were essential ingredients to achieve the quasi-elimination of T. infestans within 5 YPI and concomitant transmission blockage despite various structural threats and constraints.

Does Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida: Trypanosomatidae) modify the antennal phenotype of Triatoma dimidiata (Latreille, 1811) (Hemiptera: Triatominae)?

BACKGROUND: Triatoma dimidiata is a vector of the protozoan parasite Trypanosoma cruzi, the etiologic agent of Chagas disease. Phenotypic plasticity allows an organism to adjust its phenotype in response to stimuli or environmental conditions. Understanding the effect of T. cruzi on the phenotypic plasticity of its vectors, known as triatomines, has attracted great interest because of the implications of the parasite-triatomine interactions in the eco-epidemiology and transmission of the etiologic agent of Chagas disease. We investigated if the infection of the vector with T. cruzi may be associated with a change in the antennal phenotype of sylvatic, domestic, and laboratory-reared populations of T. dimidiata. METHODS: The abundance of each type of sensillum (bristles, basiconic, thick- and thin-walled trichoid) on the antennae of T. cruzi-infected and non-infected T. dimidiata reared in the laboratory or collected in sylvatic and domestic ecotopes were measured under light microscopy and compared using Kruskal-Wallis non-parametric tests and permutational multivariate analysis of variance. RESULTS: We found significant differences between sensilla patterns of infected and non-infected insects within sylvatic and domestic populations. Conversely, we found no significant differences between sensilla patterns of infected and non-infected insects within the laboratory-reared population. Besides, for sylvatic and domestic populations, sexual dimorphism tended to be increased in infected insects. CONCLUSION: The differences observed in infected insects could be linked to higher efficiency in the perception of odor molecules related to the search for distant mates and hosts and the flight dispersal in search of new habitats. In addition, these insects could have a positive effect on population dynamics and the transmission of T. cruzi.

Characterization of Feeding Behavior and its Relationship With the Longevity of Wild and Peridomestic Triatoma dimidiata, Latreille 1811 (Hemiptera, Reduviidae) Under Laboratory Conditions.

Triatoma dimidiata (Latreille 1811) is considered the second most important vector of the Trypanosa cruzi etiological agent of Chagas disease in Colombia. It has a life cycle that involves a domiciled, peridomiciled, and wild distribution. The study of feeding behavior and its influence on the survival of sylvatic and peridomestic populations can help identify a possible differential risk in the transmission of Chagas disease to humans, mainly in northwestern and east-central Colombia. We characterize the main parameters of feeding behavior and their influence on the longevity and survival of two rat-fed populations of T. dimidiata from Colombia, one in the north-west (from palms in a tropical dry forest area) and the other in the center-east (peridomiciliated), under controlled environmental conditions. The palm population took considerably longer than the peridomestic population to complete its life cycle under experimental laboratory conditions, being both populations univoltine since they have only one life cycle per year. Statistically significant differences were evidenced using Box-Cox model between the survival rates of T. dimidiata populations when the parameters related to blood intake and behavior were incorporated, in contrast to the survival models in which the origin only was considered as a factor. Our results could be used to generate recommendations to guide prevention strategies in communities near sylvatic and peridomiciliated populations of T. dimidiata.

The long-term impact of an Ecohealth intervention: Entomological data suggest the interruption of Chagas disease transmission in southeastern Guatemala.

Triatoma dimidiata is the main vector of Chagas disease in southern Mexico, Central America and northern South America. As a native vector, it moves readily among domestic, peri­domestic and sylvatic environments, making it difficult to control only using insecticide as this requires regular application, and re-infestation frequently occurs. Other social innovation alternatives such as those based on Ecohealth principles can be used to tackle the dynamics of the disease in an integral way. We asked whether an Ecohealth intervention, implemented beginning in 2001 in a highly infested village, 41.8%, in southeastern Guatemala, was sustainable in the long term. This intervention included initial insecticide treatments, followed by making low-cost house improvements to eliminate transmission risk factors such as repairing cracked walls, covering dirt floors with a cement-like substance and moving domestic animals outside. We assessed the long-term sustainability through entomological and house condition surveys, as well as an analysis of community satisfaction. We found over a 19-year period, infestation with T. dimidiata was reduced to 2.2% and maintained at a level below the level (8%) where vector transmission is unlikely. This long-term maintenance of low infestation coincided with a large proportion of villagers (88.6%) improving their houses and completing other aspects of the Ecohealth approach to maintain the village at low risk for Chagas transmission. There was unanimous satisfaction among the villagers with their houses, following improvements using the Ecohealth method, which likely played a role in the long-term persistence of the modifications. Although the infestation has remained low, 11 years following the last intervention and as the population grew there has been an increase in the proportion of "at-risk" houses, to 33%, pointing out the necessity of maintaining vigilance. The Ecohealth approach is a low-cost, sustainable approach for the long-term control of vector-borne Chagas disease. We recommend this approach including ongoing community monitoring and institutional response for the long-term, integrated control of Chagas disease.

Body shape and fluctuating asymmetry following different feeding sources and feeding time in a triatomine, Triatoma pallidipennis (Stål, 1892).

Even when an animal has a generalist diet, different food sources can impact its body shape and fluctuating asymmetry (a stress indicator; FA). To test this, we varied the food source (mammalian, avian or defibrinated mammalian blood; and control animals - ad libitum feeding) and the time of feeding (every 8 days, 45 days and ad libitum) having the Chagas triatomine vector, Triatoma pallidipennis (Stål, 1892), as a study animal which has presumable generalist feeding habits. This factorial design was applied since first instar animals until adulthood. As response variables, we measured body shape and FA in adults of both sexes, using a two-dimensional geometric morphometrics protocol. The highest variance in body shape was explained by diet (17%), followed by sex nested within diet (12%). Males had less morphological differentiation than females: females with defibrinated blood provided every 45 days differentiated more, while those that fed on mammalian blood every 8 days differed less. Distances among the averages of the FA component related to shape indicated greater distances between avian blood provided every 45 days and mammalian blood provided every 8 days, as well as between the two groups fed on avian blood (feeding every 8 and 45 days), followed by avian and defibrinated blood, both fed every 8 days. These results indicate that blood source and feeding time have significant effects on the body shape, and FA in females and both sexes. Thus, despite general feeding habits, avian blood showed a greater impact on shape and FA in triatomines. This may select for triatomines to use mammal blood rather than avian blood if they have the chance to do so.

The connection between Trypanosoma cruzi transmission cycles by Triatoma brasiliensis brasiliensis: A threat to human health in an area susceptible to desertification in the Seridó, Rio Grande do Norte, Brazil.

An outbreak of Chagas disease, possibly involving its vector Triatoma brasiliensis brasiliensis, was identified in the state of Rio Grande do Norte (RN). Given the historical significance of this vector in public health, the study aimed to evaluate its role in the transmission dynamics of the protozoan Trypanosoma cruzi in an area undergoing desertification in the Seridó region, RN, Brazil. We captured triatomines in sylvatic and anthropic ecotopes. Natural vector infection was determined using parasitological and molecular methods and we identified discrete typing units (DTUs) of T. cruzi by analyzing the COII gene of mtDNA, 24Sα rDNA, and mini-exon gene. Their blood meals sources were identified by amplification and sequencing of the mtDNA cytochrome b gene. A total of 952 T. b. brasiliensis were captured in peridomestic (69.9%) and sylvatic ecotopes (30.4%). A wide range of natural infection rates were observed in peridomestic (36.0% - 71.1%) and sylvatic populations (28.6% - 100.0%). We observed the circulation of TcI and TcII DTUs with a predominance of Tcl in sylvatic and peridomestic environments. Kerodon rupestris, rocky cavy (13/39), Homo sapiens, human (8/39), and Bos taurus, ox (6/39) were the most frequently detected blood meals sources. Thus, Triatoma b. brasiliensis is invading and colonizing the human dwellings. Furthermore, high levels of natural infection, coupled with the detection of TcI and TcII DTUs, and also the detection of K. rupestris and H. sapiens as blood meals sources of infected T. b. brasiliensis indicate a risk of T. cruzi transmission to human populations in areas undergoing desertification.