Gran Chaco Region Research Articles

South America is becoming warmer, drier, and more flammable

South America is experiencing severe impacts from climate change. Although the warming of the subcontinent closely follows the global path, the rise of temperatures has been more pronounced in some regions, which have also seen a parallel increment in the occurrence of droughts and weather conditions associated with enhanced fire risk. Here, we use reanalysis datasets to analyze the progression of the concurring warm, dry, and high fire risk conditions (i.e., dry compounds) since 1971. We show that the frequency of these compound extremes has surged in key South American regions including the northern Amazon, which have seen a 3-fold increase in the number of days per year with extreme fire weather conditions (including high temperatures, dryness, and low humidity). Our results also suggest that the surface temperature of the tropical Pacific Ocean modulates the interannual variability of dry compounds in South America. While El Niño enhances the fire risk in the northern Amazon, dry extremes in the Gran Chaco region appear to be more responsive to La Niña.

Employing scientific evidence through synthetic indices to support management and conservation policies for an endangered tree of the Gran Chaco

Management and conservation programs require accessible scientific evidence to effectively plan and achieve their goals. Facing regional and species-specific threats, Gonopterodendron sarmientoi, an endangered tree native to the Gran Chaco region, requires scientific evidence to support management and conservation actions, notably in forest management and territorial planning. To bridge this crucial gap, we developed indices that integrate genetic, evolutionary, morphological, threat-related, and ethnobotanical data concerning G. sarmientoi at a landscape level. Across twenty-four localities of this species, we have created four distinct indices. The first index amalgamates data on genetics, functional traits, and paleoclimate information. The second index incorporates data on threats stemming from deforestation and climate change scenarios. The third index provides supplementary insights into the species’ utilization by indigenous groups. Finally, the fourth index combines all the aforementioned data to prioritize the most valuable and threatened localities. Through this comprehensive approach, we have identified specific in-situ and ex-situ management and conservation actions for G. sarmientoi. This approach considers broader-scale conservation efforts and considers large-scale variations and processes. The indices effectively link scientific data with actionable insights, providing decision-makers involved with G. sarmientoi with concise information that encapsulates the most pertinent aspects of species conservation.

“Towards the East, Towards Jerusalem”

In this paper, archaeo- and ethnoastronomical methods are used to investigate the orientation of synagogues, graves and prayer among Ashkenazi Jewish communities in the central-northern part of the Argentinian Province of Santa Fe, in the southern Gran Chaco region of South America. These communities have their origin in Jewish agricultural colonies, which were established by immigrants from central and eastern Europe who arrived during the late nineteenth and early twentieth centuries. The study shows the complexity of the logics involved in the construction of the meaning of spatial orientations in local Jewish religious practices, and also the necessity of ethnographic surveys as a complement to quantitative studies of orientations.

A Possible Case of Coccidioides Infection in a Thirteenth-Century Bolivian Mummy

Coccidioidomycosis is an infectious fungal disease endemic in Bolivia's Gran Chaco region that is caused by inspiration of the spores of Coccidiodes species. It is a respiratory pathology that can spread to the skeleton and produce diffuse lytic lesions in different parts of the body. This disease has rarely been described in historic populations, and we present here a new case of coccidioidomycosis in a mummified human individual. It corresponds to a female individual with an age at death of 25–35 years, dated to the Tiwanaku epoch of the thirteenth century AD. It was found inside a sepulchral cave near the city of Ulloma in western Bolivia. Radiographic examination shows numerous osseous lytic lesions with central cavitation concentrated on the cranial table and vertebral bodies. The observed condition could correspond to the secondary phase of coccidioidomycosis. This diagnosis is noteworthy because coccidioidomycosis was mainly described as a male work-related disease and has never been found in ancient western Bolivia.

A mathematical model for Chagas disease transmission with neighboring villages

Chagas disease has been the target of widespread control programs, primarily through residual insecticide treatments. However, in some regions like the Gran Chaco, these efforts have failed to sufficiently curb the disease. Vector reinfestation into homes and vector resistance to insecticides are possible causes of the control failure. This work proposes a mathematical model for the dynamics of Chagas disease in neighboring rural villages of the Gran Chaco region, incorporating human travel between the villages, passive vector migration, and insecticide resistance. Computational simulations across a wide variety of scenarios are presented. The simulations reveal that the effects of human travel and passive vector migration are secondary and unlikely to play a significant role in the overall dynamics, including the number of human infections. The numerical results also show that insecticide resistance causes a notable increase in infections and is an especially important source of reinfestation when spraying stops. The results suggest that control strategies related to migration and travel between the villages are unlikely to yield meaningful benefit and should instead focus on other reinfestation sources like domestic foci that survive insecticide spraying or sylvatic foci.

The Pampa del Indio project: sustainable vector control and long-term declines in the prevalence and abundance of Triatoma infestans infected with Trypanosoma cruzi in the Argentine Chaco

BackgroundThe Gran Chaco region is a major hotspot of Chagas disease. We implemented a 9-year program aimed at suppressing house infestation with Triatoma infestans and stopping vector-borne transmission to creole and indigenous (Qom) residents across Pampa del Indio municipality (Argentine Chaco). The aim of the present study was to assess the intervention effects on parasite-based transmission indices and the spatial distribution of the parasite, and test whether house-level variations in triatomine infection with Trypanosoma cruzi declined postintervention and were influenced by household ethnicity, persistent infestation linked to pyrethroid resistance and other determinants of bug infection.MethodsThis longitudinal study assessed house infestation and bug infection with T. cruzi before and after spraying houses with pyrethroids and implemented systematic surveillance-and-response measures across four operational areas over the period 2007–2016. Live triatomines were individually examined for infection by optical microscopy or kinetoplast DNA (kDNA)-PCR and declared to be infected with T. cruzi when assessed positive by either method.ResultsThe prevalence of infection with T. cruzi was 19.4% among 6397 T. infestans examined. Infection ranged widely among the study areas (12.5–26.0%), household ethnicity (15.3–26.9%), bug ecotopes (1.8–27.2%) and developmental stages (5.9–27.6%), and decreased from 24.1% (baseline) to 0.9% (endpoint). Using random-intercept multiple logistic regression, the relative odds of bug infection strongly decreased as the intervention period progressed, and increased with baseline domestic infestation and bug stage and in Qom households. The abundance of infected bugs and the proportion of houses with ≥ 1 infected bug remained depressed postintervention and were more informative of area-wide risk status than the prevalence of bug infection. Global spatial analysis revealed sharp changes in the aggregation of bug infection after the attack phase. Baseline domestic infestation and baseline bug infection strongly predicted the future occurrence of bug infection, as did persistent domestic infestation in the area with multiple pyrethroid-resistant foci. Only 19% of houses had a baseline domestic infestation and 56% had ever had ≥ 1 infected bug.ConclusionsPersistent bug infection postintervention was closely associated with persistent foci generated by pyrethroid resistance. Postintervention parasite-based indices closely agreed with human serosurveys at the study endpoint, suggesting transmission blockage. The program identified households and population subgroups for targeted interventions and opened new opportunities for risk prioritization and sustainable vector control and disease prevention.Graphical abstract

Chagas prevention and control in an endemic area from the Argentinian Gran Chaco Region: Data from 14 years of uninterrupted intervention.

Chagas Disease (ChD) is a Neglected Tropical Disease (NTD) affecting 6 to 7 million people worldwide, mostly from Latin America. In Argentina, a national control program has been implemented since 1962, yet there are still an estimated 1.6 million infected individuals. Control programs were based almost exclusively on entomological surveillance and chemical control of households and were not continuous given a lack of coordination and resources. Argentina´s ChD program was originally vertical and centralized; later, it was partially and, in general, unsuccessfully transferred to the provinces. Herein, we describe the implementation of a control program for ChD with an ecohealth approach in rural settlements around the city of Añatuya, Santiago del Estero. The program included yearly household visits for entomological surveillance and control, health promotion workshops, and structural house improvements. Improved structures included internal and external walls and roofs, as well as the construction of water wells and latrines, and the organization and improvement of peri-domestic structures. Activities were carried out by specifically trained personnel except for house improvements, which were performed by the community, under technical guidance and provision of materials. Data was collected using standardized questionnaires for household characterization, entomological infestation status and chemical control activities. This program was continuously implemented since 2005 with high community participation and adherence, incorporating 13 settlements and 502 households. During the surveillance phase, 4,193 domiciliary inspections were performed, and both the intra- and peri-domestic infestation rate were reduced from 17.9% to 0.2% (P < 0.01) and from 20.4% to 3%, respectively. Additionally, 399 households were structurally improved. The program is still ongoing and, after 14 years of implementation, has built social networks and collaboration between implementers and beneficiaries with a reduction of T. infestans infestation in the intra- and peri-domicile. This reduction, especially inside the household, has enabled access to diagnosis and treatment of the population, with minimal risk of re-infection.

Marginal risk of domestic vector-borne Trypanosoma cruzi transmission after improved vector control of Triatoma infestans across a rural-to-urban gradient in the Argentine Chaco

The interruption of domestic vector-borne transmission of Trypanosoma cruzi in the Americas remains one of the main goals of the World Health Organization 2021–2030 road map for neglected tropical diseases. We implemented a longitudinal intervention program over 2015–2022 to suppress (peri)domestic Triatoma infestans in the municipality of Avia Terai, Chaco Province, Argentina and found that house infestation (3851 houses inspected) and triatomine abundance decreased over the first 2 years post-intervention (YPI), and remained stable thereafter associated to moderate pyrethroid resistant foci. Here we assessed selected components of transmission risk after interventions across the rural-to-urban gradient. We used multistage random sampling to select a municipality-wide sample of T. infestans. We examined 356 insects collected in 87 houses for T. cruzi infection using kDNA-PCR and identified their bloodmeal sources using an indirect ELISA. The overall prevalence of T. cruzi infection post-intervention was 1.7% (95% CI 0.7–3.6). Few houses (5.7%) (95% CI 2.5–12.8) harbored infected triatomines across the gradient. Infected triatomines were found in 5 peri‑urban or rural dwellings over 1–4 years post-intervention. No infected insect was found in the urban area. The human blood index decreased from 66.2 at baseline to 42.8 at 1YPI and then increased to 92.9 at 4–5 YPI in the few infested domiciles detected. The percentage of houses with human-fed bugs displayed a similar temporal trend. Our results indicate marginal risks of domestic vector-borne transmission across the district after implementation of the intervention program. Ensuring sustainable vector surveillance coupled with human etiological diagnosis and treatment in hiperendemic areas like the Gran Chaco region, is urgently needed.252 words

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

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. 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. 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. 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.

Microencapsulation of a Native Strain of the Entomopathogenic Fungus Beauveria bassiana and Bioinsecticide Activity against Pyrethroid-Resistant Triatoma infestans to Vector Control of Chagas Disease in the Argentine Gran Chaco Region.

The blood-sucking bug Triatoma infestans is the main Chagas disease vector in the Southern Cone of Latin America. Populations resistant to pyrethroid insecticides have been detected in the early 2000s and then expanded to the endemic area of northern Salta province, Argentina. In this context, the entomopathogenic fungus Beauveria bassiana has been shown to be pathogenic to pyrethroid-resistant T. infestans. In this study, both the bioinsecticidal activity and the residual effect of an alginate-based microencapsulation of a native strain of B. bassiana (Bb-C001) were tested under semi-field conditions against pyrethroid-resistant T. infestans nymphs. Fungal microencapsulated formulation caused higher nymph mortality than the unmicroencapsulated fungus and contributed to maintaining the conidial viability throughout the period evaluated under the tested conditions. These results suggest that alginate microencapsulation is an effective, simple, low-cost method that could be incorporated into the formulation of a bioinsecticide as a strategy to reduce the vector transmission of Chagas disease.

On the banks of the Pilcomayo River: Wichí fishery in the age of motorcycles

In just a few years motorcycles had become an irreplaceable object for the daily life of Indigenous people in the Gran Chaco region. In spite of their pervasiveness, there are still many aspects to this current dissemination that remain to be unraveled. This paper explores the ways in which motorcycles have been incorporated into Indigenous material culture and the ways they are reshaping Indigenous perceptions and relations with the local environment. Starting from the machines and their uses is a way to not confine Indigenous people to a position as victims of modernity, but rather to recognize their proactive role in the ongoing reproduction and transformation of their cultural world. For this purpose, I take the example of the Wichí fishery to see how this cultural practice is changing as fishermen adopt motorcycles as means of transport. I investigate this practice and its transformations based on ethnographic fieldworks carried out with several communities settled on the banks of the Pilcomayo River, as well as readings of the ethnological literature which contains detailed descriptions of this practice. By tracing its past and ongoing transformations, I show how the hold and spatial organization of Wichí fishery has evolved as motorcycles spread to the whole Pilcomayo area. Their adoption redefines fishermen perceptions and relations with the surrounding environment, which is now understood from a new mechanized and motorized perspective of capitalization and exploitation. Indeed, while motorcycles allow them to integrate into the market, they further promote market penetration on Indigenous lands. At the same time, I demonstrate how motorcycles allow fishermen to overcome the inconveniences of an intractable river and new infrastructures that hinder fishing practices, as well as to bypass the attempts to privatize the riverbanks. In a way, the fishermen are more resilient to these sudden changes thanks to motorcycles.

Epigenetic aging differences between Wichí and Criollos from Argentina: Insights from genomic history and ecology.

Epigenetic estimators based on DNA methylation levels have emerged as promising biomarkers of human aging. These estimators exhibit natural variations across human groups, but data about indigenous populations remain underrepresented in research. This study aims to investigate differences in epigenetic estimators between two distinct human populations, both residing in the Gran Chaco region of Argentina, the Native-American Wichí, and admixed Criollos who are descendants of intermarriages between Native Americans and the first European colonizers, using a population genetic approach. We analyzed 24 Wichí (mean age: 39.2 ± 12.9 yo) and 24 Criollos (mean age: 41.1 ± 14.0 yo) for DNA methylation levels using the Infinium MethylationEPIC (Illumina) to calculate 16 epigenetic estimators. Additionally, we examined genome-wide genetic variation using the HumanOmniExpress BeadChip (Illumina) to gain insights into the genetic history of these populations. Our results indicate that Native-American Wichí are epigenetically older compared to Criollos according to five epigenetic estimators. Analyses within the Criollos population reveal that global ancestry does not influence the differences observed, while local (chromosomal) ancestry shows positive associations between specific SNPs located in genomic regions over-represented by Native-American ancestry and measures of epigenetic age acceleration (AgeAccelHannum). Furthermore, we demonstrate that differences in population ecologies also contribute to observed epigenetic differences. Overall, our study suggests that while the genomic history may partially account for the observed epigenetic differences, non-genetic factors, such as lifestyle and ecological factors, play a substantial role in the variability of epigenetic estimators, thereby contributing to variations in human epigenetic aging.

Influence of land‐use changes on microbial community structure and diversity in a semiarid region

AbstractLand‐use change and the conversion of land into croplands is one of the main drivers of soil degradation and the loss of soil organic carbon. Few studies have evaluated the impact of the expansion of the agricultural frontier on soil microbial communities in the Gran Chaco region in South America; therefore, the objective of this study was to explore how soil microbial communities respond to land‐use changes in a semiarid region of Argentina. The land uses selected were total and selective clearing with livestock (TC‐livestock and SC‐livestock), total clearing with agriculture (TC‐agriculture), and an undisturbed site (R‐Chancaní). Our results suggest that microbial abundances were strongly influenced by seasonal changes. In both seasons, the lowest values of total microbial biomass were observed in TC‐agriculture and TC‐livestock. In the wet season, TC‐agriculture had the lowest fungal abundance, and both total clearing sites (TC‐livestock and TC‐agriculture) had higher bacterial abundance than the other sites. Our data also showed that the Shannon and richness indices were highest at the farming sites, indicating a similar tendency in the diversity indexes in both dry and wet seasons. According to Pearson correlation analysis, humic substance (HS) content was a key driver influencing soil microbial communities, demonstrating that high HS content may significantly increase bacteria, fungi, and total phospholipid fatty acids. Microbial composition highly depended on seasonal changes. Overall, our results suggest that land‐use change altered microbial community structure and bacterial diversity, and that HS content played a crucial role in driving changes in soil microbial composition.

Foraging behavior of Argentine Criollo and Angus cows grazing semi-desert rangelands in the Arid Gran Chaco region of Argentina

We monitored grazing behavior and habitat selection of Argentine Criollo (AC), South American heritage cattle breed, and Angus (AA) cows during summer and winter of 2016 (wetter year) and 2017 (drier year) at a site in La Rioja, Argentina. In each year and season, five AC and five AA cows were fitted with GPS collars configured to log animal position at 10-min intervals for 40 days. Movement, activity, and vegetation use patterns of each breed were derived from the GPS data. In summer, AC cows traveled similar daily distances, explored smaller (wetter year) or slightly larger (drier year) areas of the pasture, tended to move along more sinuous path trajectories, and showed stronger selection of the vegetation unit with higher forage quality and lowest woody cover compared to AA counterparts. AC cows allocated similar (wetter year) or more time to graze (drier year), allocated roughly the same amount of time to travel, and spent similar (wetter year) or less time resting (drier year) than AA cows. In winter, foraging behavior differences between breeds were only observed in the drier year. AC cows traveled farther and spent less time resting than AA counterparts that year. When comparing summer vs. winter movement patterns of each breed, AC cows showed an apparent greater ability to adapt to changing forage conditions (foraging plasticity) compared to AA counterparts which appeared to exhibit more rigid foraging patterns. Criollo cattle could be a tool to increase the resilience of Arid Chaco beef systems in the face of climate change. The rangeland conservation implications of raising Criollo vs. British beef cattle require further investigation.

Chagas disease in children from the Gran Chaco region: A bibliographic appraisal.

In the Gran Chaco region, the Pan American Health Organization (PAHO) declared the interruption of vector transmission of Chagas Disease in Paraguay and some district of Argentina.After a bibliographic search, by using the words "Chagas, prevalence, children, Chaco", on scientiphic articles indexed in Pubmed and Lilacs during the 2010-2021 period, we found nine studies which dealt with entomological data seroprevalence surveys of Chagas Disease in Argentine children and three studies in Bolivian children.More field studies need to be published to better understand the epidemiological situation in children from the region. Due to its social and ecological characteristics, the Gran Chaco region remains a hotspot for Chagas Disease affecting disproportionally rural communities and certain vulnerable ethnics groups.

Dynamics of Triatoma infestans populations in the Paraguayan Chaco: Population genetic analysis of household reinfestation following vector control.

BackgroundAlthough domestic infestations by Triatoma infestans have been successfully controlled across Latin America, in areas of the Gran Chaco region, recurrent post-spraying house colonization continues to be a significant challenge, jeopardizing Chagas disease vector control and maintaining active Trypanosoma cruzi transmission.Methodology/Principal findingsTo investigate the dynamics of triatomine reinfestation in a rural area of the Paraguayan Chaco, genetic characterization (based on 10 microsatellite loci and cytochrome B sequence polymorphisms) was performed on baseline and reinfestant T. infestans (n = 138) from four indigenous communities and adjacent sylvatic sites. House quality and basic economic activities were assessed across the four communities. Significant genetic differentiation was detected among all baseline triatomine populations. Faster reinfestation was observed in the communities with higher infestation rates pre-spraying. Baseline and reinfestant populations from the same communities were not genetically different, but two potentially distinct processes of reinfestation were evident. In Campo Largo, the reinfestant population was likely founded by domestic survivor foci, with reduced genetic diversity relative to the baseline population. However, in 12 de Junio, reinfestant bugs were likely derived from different sources, including survivors from the pre-spraying population and sympatric sylvatic bugs, indicative of gene-flow between these habitats, likely driven by high human mobility and economic activities in adjacent sylvatic areas.Conclusions/SignificanceOur results demonstrate that sylvatic T. infestans threatens vector control strategies, either as a reinfestation source or by providing a temporary refuge during insecticide spraying. Passive anthropogenic importation of T. infestans and active human interactions with neighboring forested areas also played a role in recolonization. Optimization of spraying, integrated community development and close monitoring of sylvatic areas should be considered when implementing vector control activities in the Gran Chaco.

Improved vector control of Triatoma infestans limited by emerging pyrethroid resistance across an urban-to-rural gradient in the Argentine Chaco

BackgroundThe sustainable elimination of Triatoma infestans in the Gran Chaco region represents an enduring challenge. Following the limited effects of a routine pyrethroid insecticide spraying campaign conducted over 2011–2013 (first period) in Avia Terai, an endemic municipality with approximately 2300 houses, we implemented a rapid-impact intervention package to suppress house infestation across the urban-to-rural gradient over 2015–2019 (second period). Here, we assess their impacts and whether persisting infestations were associated with pyrethroid resistance.MethodsThe 2011–2013 campaign achieved a limited detection and spray coverage across settings (< 68%), more so during the surveillance phase. Following community mobilization and school-based interventions, the 2015–2019 program assessed baseline house infestation using a stratified sampling strategy; sprayed all rural houses with suspension concentrate beta-cypermethrin, and selectively sprayed infested and adjacent houses in urban and peri-urban settings; and monitored house infestation and performed selective treatments over the follow-up.ResultsOver the first period, house infestation returned to pre-intervention levels within 3–4 years. The adjusted relative odds of house infestation between 2011–2013 and 2015–2016 differed very little (adj. OR: 1.17, 95% CI 0.91–1.51). Over the second period, infestation decreased significantly between 0 and 1 year post-spraying (YPS) (adj. OR: 0.36, 95% CI 0.28–0.46), with heterogeneous effects across the gradient. Mean bug abundance also dropped between 0 and 1 YPS and thereafter remained stable in rural and peri-urban areas. Using multiple regression models, house infestation and bug abundance at 1 YPS were 3–4 times higher if the house had been infested before treatment, or was scored as high-risk or non-participating. No low-risk house was ever infested. Persistent foci over two successive surveys increased from 30.0 to 59.3% across the gradient. Infestation was more concentrated in peridomestic rather than domestic habitats. Discriminating-dose bioassays showed incipient or moderate pyrethroid resistance in 7% of 28 triatomine populations collected over 2015–2016 and in 83% of 52 post-spraying populations.ConclusionsThe intervention package was substantially more effective than the routine insecticide spraying campaign, though the effects were lower than predicted due to unexpected incipient or moderate pyrethroid resistance. Increased awareness and diagnosis of vector control failures in the Gran Chaco, including appropriate remedial actions, are greatly needed.Graphical abstract

Indoor residual spraying practices against Triatoma infestans in the Bolivian Chaco: contributing factors to suboptimal insecticide delivery to treated households

BackgroundIndoor residual spraying (IRS) of insecticides is a key method to reduce vector transmission of Trypanosoma cruzi, causing Chagas disease in a large part of South America. However, the successes of IRS in the Gran Chaco region straddling Bolivia, Argentina, and Paraguay, have not equalled those in other Southern Cone countries.AimsThis study evaluated routine IRS practices and insecticide quality control in a typical endemic community in the Bolivian Chaco.MethodsAlpha-cypermethrin active ingredient (a.i.) captured onto filter papers fitted to sprayed wall surfaces, and in prepared spray tank solutions, were measured using an adapted Insecticide Quantification Kit (IQK™) validated against HPLC quantification methods. The data were analysed by mixed-effects negative binomial regression models to examine the delivered insecticide a.i. concentrations on filter papers in relation to the sprayed wall heights, spray coverage rates (surface area / spray time [m2/min]), and observed/expected spray rate ratios. Variations between health workers and householders’ compliance to empty houses for IRS delivery were also evaluated. Sedimentation rates of alpha-cypermethrin a.i. post-mixing of prepared spray tanks were quantified in the laboratory.ResultsSubstantial variations were observed in the alpha-cypermethrin a.i. concentrations delivered; only 10.4% (50/480) of filter papers and 8.8% (5/57) of houses received the target concentration of 50 mg ± 20% a.i./m2. The delivered concentrations were not related to those in the matched spray tank solutions. The sedimentation of alpha-cypermethrin a.i. in the surface solution of prepared spray tanks was rapid post-mixing, resulting in a linear 3.3% loss of a.i. content per minute and 49% loss after 15 min. Only 7.5% (6/80) of houses were sprayed at the WHO recommended rate of 19 m2/min (± 10%), whereas 77.5% (62/80) were sprayed at a lower than expected rate. The median a.i. concentration delivered to houses was not significantly associated with the observed spray coverage rate. Householder compliance did not significantly influence either the spray coverage rates or the median alpha-cypermethrin a.i. concentrations delivered to houses.ConclusionsSuboptimal delivery of IRS is partially attributable to the insecticide physical characteristics and the need for revision of insecticide delivery methods, which includes training of IRS teams and community education to encourage compliance. The IQK™ is a necessary field-friendly tool to improve IRS quality and to facilitate health worker training and decision-making by Chagas disease vector control managers.Graphical

Motherese in the Wichi Language (El maternés en la lengua wichí)

This paper provides the first evidence of maternal speech — motherese — in Wichi, an indigenous language with a complex morphology spoken in the Gran Chaco region of Argentina. The corpus consists of 22 hours of video recordings from the daily life of three children, starting from their one-morpheme utterance period (MLU = 1) to the onset of combining early morphemes (MLU = 2.30). Employing a mixed methodological approach, results allowed us: (a) to create an observational system of specific categories for the analysis of the maternal speech in Wichi; (b) to identify motherese in Wichi, noticeably stable across cases and organized into constellations of lexical, pragmatic-discursive and prosodic features with changes and continuities during the developmental target period. The results are discussed cross-culturally in the light of a renewed cultural approach, while limitations and future directions are addressed.

Evaluation of the Production Potential of Bio-Oil from Quebracho Colorado Sawdust from Tannin Extraction Industry

A conventional laboratory-scale pyrolysis process is introduced to produce fuels from spent quebracho colorado sawdust (Schinopsis balansae and Schinopsis lorentzii). This raw material is a forest industry residue from the Gran Chaco region. Conditioning and chemical characterization to predict the products of the raw material chosen were first performed. The lignocellulosic residue has approximately 51.03% total structural carbohydrates, 30.47% of lignin and lower percentages of other compounds. The pyrolysis fixed bed reactor features 49.7% liquid product yield, 23.8% solids and 26.5% gases. The pyrolysis liquid product obtained is a mix of aqueous phase (bio-oil) and oil phase (tar). Higher Heating Value (HHV) of this mixture resulted from 31.5 MJ/kg with a density of 1.05 Kg/dm 3 . Both phases, bio-oil and tar, of the pyrolysis liquid product from spent quebracho colorado sawdust showed low concentrations of carboxylic acids. The upper phase (bio-oil) presented 29% of phenolic compounds, 34% of carbonyl compounds and 27% of methoxylated aromatic compounds. The lower phase (tar) presented 49%, 18% and 56% of phenolic compounds, carbonyl compounds and methoxylated aromatic compounds, respectively.