Humans seropositive for Trypanosoma cruzi co-infected with intestinal helminths have higher infectiousness, parasitaemia and Th2-type response in the Argentine Chaco.

BACKGROUND: The Gran Chaco ecoregion is a well-known hotspot of several neglected tropical diseases (NTDs) including Chagas disease, soil-transmitted helminthiasis and multiparasitic infections. Interspecific interactions between parasite species can modify host susceptibility, pathogenesis and transmissibility through immunomodulation. Our objective was to test the association between human co-infection with intestinal parasites and host parasitaemia, infectiousness to the vector and immunological profiles in Trypanosoma cruzi-seropositive individuals residing in an endemic region of the Argentine Chaco. METHODS: We conducted a cross-sectional serological survey for T. cruzi infection along with an intestinal parasite survey in two adjacent rural villages. Each participant was tested for T. cruzi and Strongyloides stercoralis infection by serodiagnosis, and by coprological tests for intestinal parasite detection. Trypanosoma cruzi bloodstream parasite load was determined by quantitative PCR (qPCR), host infectiousness by artificial xenodiagnosis and serum human cytokine levels by flow cytometry. RESULTS: The seroprevalence for T. cruzi was 16.1% and for S. stercoralis 11.5% (n = 87). We found 25.3% of patients with Enterobius vermicularis. The most frequent protozoan parasites were Blastocystis spp. (39.1%), Giardia lamblia (6.9%) and Cryptosporidium spp. (3.4%). Multiparasitism occurred in 36.8% of the examined patients. Co-infection ranged from 6.9% to 8.1% for T. cruzi-seropositive humans simultaneously infected with at least one protozoan or helminth species, respectively. The relative odds of being positive by qPCR or xenodiagnosis (i.e. infectious) of 28 T. cruzi-seropositive patients was eight times higher in people co-infected with at least one helminth species than in patients with no such co-infection. Trypanosoma cruzi parasite load and host infectiousness were positively associated with helminth co-infection in a multiple regression analysis. Interferon-gamma (IFN-γ) response, measured in relation to interleukin (IL)-4 among humans infected with T. cruzi only, was 1.5-fold higher than for T. cruzi-seropositive patients co-infected with helminths. The median concentration of IL-4 was significantly higher in T. cruzi-seropositive patients with a positive qPCR test than in qPCR-negative patients. CONCLUSIONS: Our results show a high level of multiparasitism and suggest that co-infection with intestinal helminths increased T. cruzi parasitaemia and upregulated the Th2-type response in the study patients.

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.

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.

BACKGROUND: The 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. METHODS: This 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. RESULTS: The 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. CONCLUSIONS: Persistent 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.

EVALUATION OF A COMBINATION OF TILETAMINE-ZOLAZEPAM, MEDETOMIDINE, AND AZAPERONE WITH NASAL OXYGEN SUPPLEMENTATION FOR THE IMMOBILIZATION OF CAPTIVE CHACOAN PECCARIES (CATAGONUS WAGNERI) IN THE CHACO REGION OF PARAGUAY.

A combination of tiletamine-zolazepam, medetomidine, and azaperone was used to immobilize captive Chacoan peccaries (Catagonus wagneri) for health assessments and biological sample collection at the Centro Chaqueño para la Conservación e Investigación (CCCI) in the Paraguayan Chaco during July in 2017 and 2018. In total, 83 peccaries kept in 0.25-1.50 hectare enclosures were immobilized via dart-administered anesthetic. Mean animal weight was 33.89±3.74 kg (standard deviation; n=77). The mean intramuscular (IM) anesthetic drug and dosages were 0.03±0.00 mg/kg of medetomidine, 0.91±0.10 mg/kg of Zoletil 50 (tiletamine-zolazepam), and 0.30±0.03 mg/kg azaperone. The mean time to recumbency after darting was 6.07±2.65 min. The mean time to reach the anesthetic plane postdarting was 10.00±2.00 min. Muscle relaxation was adequate to allow minor veterinary procedures. A mean dosage of 0.15±0.02 mg/kg of atipamezole was given IM to reverse the medetomidine. Recoveries were smooth and animals were standing by 59.17±30.18 min postreversal. Full recovery and release back to enclosures occurred 90±30 min postreversal. A single dose of this drug combination provided adequate anesthesia for 88% of adult Chacoan peccaries; 12% needed a supplemental dose of tiletamine-zolazepam because of failure to receive the full dose from the anesthetic dart. Sex and age did not impact the dosage required to achieve immobilization. Confinement during recovery from anesthesia is required with this protocol. Aside from mild hypoxemia, no adverse effects from anesthesia were observed. However, oxygen supplementation as a part of this protocol is recommended to support circulatory and respiratory capacity.

Treatment of dogs with fluralaner reduced pyrethroid-resistant Triatoma infestans abundance, Trypanosoma cruzi infection and human-triatomine contact in the Argentine Chaco.

BACKGROUND: Triatomine elimination efforts and the interruption of domestic transmission of Trypanosoma cruzi are hampered by pyrethroid resistance. Fluralaner, a long-lasting ectoparasiticide administered to dogs, substantially reduced site infestation and abundance of pyrethroid-resistant Triatoma infestans Klug (Heteroptera: Reduviidae) in an ongoing 10-month trial in Castelli (Chaco Province, Argentina). We assessed the effects of fluralaner on vector infection with T. cruzi and blood meal sources stratified by ecotope and quantified its medium-term effects on site infestation and triatomine abundance. METHODS: We conducted a placebo-controlled, before-and-after efficacy trial of fluralaner in 28 infested sites over a 22-month period. All dogs received either an oral dose of fluralaner (treated group) or placebo (control group) at 0 month post-treatment [MPT]. Placebo-treated dogs were rescue-treated with fluralaner at 1 MPT, as were all eligible dogs at 7 MPT. Site-level infestation and abundance were periodically assessed by timed manual searches with a dislodging aerosol. Vector infection was mainly determined by kDNA-PCR and blood meal sources were determined by enzyme-linked immunosorbent assay. RESULTS: In fluralaner-treated households, site infestation dropped from 100% at 0 MPT to 18-19% over the period 6-22 MPT while mean abundance plummeted from 5.5 to 0.6 triatomines per unit effort. In control households, infestation dropped similarly post-treatment. The overall prevalence of T. cruzi infection steadily decreased from 13.8% at 0-1 MPT (baseline) to 6.4% and subsequently 2.3% thereafter, while in domiciles, kitchens and storerooms it dropped from 17.4% to 4.7% and subsequently 3.3% thereafter. Most infected triatomines occurred in domiciles and had fed on humans. Infected-bug abundance plummeted after fluralaner treatment and remained marginal or nil thereafter. The human blood index of triatomines collected in domiciles, kitchens and storerooms highly significantly fell from 42.9% at baseline to 5.3-9.1% over the period 6-10 MPT, increasing to 36.8% at 22 MPT. Dog blood meals occurred before fluralaner administration only. The cat blood index increased from 9.9% at baseline to 57.9-72.7% over the period 6-10 MPT and dropped to 5.3% at 22 MPT, whereas chicken blood meals rose from 39.6% to 63.2-88.6%. CONCLUSION: Fluralaner severely impacted infestation- and transmission-related indices over nearly 2 years, causing evident effects at 1 MPT, and deserves larger efficacy trials.

Hydrogeological and hydrochemical framework of the distal section of the Salado-Juramento fluvial megafan (Bajos Submeridionales) in South America.

The Bajos Submeridionales (BBSS) (Argentina) is a 54,800 km2 hydrological system located at the distal part of the Salado-Juramento Fluvial Megafan (SJRM). Its climate evolves from humid-subtropical in the east to semiarid in the west. Its hydrogeological system is typical of extensive plains, topography locally imposes vertical flows and neotectonic elements define system boundaries and drains. These characteristics and poor data availability represent a major challenge for identifying a hierarchical subsurface flow system and the influence of neotectonics. This work characterizes the hydrogeology of the BBSS and proposes a conceptual model based on integrated systematic information including 453 water level, 145 hydrochemical, and 99 δ18O- δD data. Four hydrogeological units are identified (HU1-HU4), two of which are divided into sub-units based on their sedimentary sequence. The main chemical types are Na-Cl, Na-Cl/SO4, Na-HCO3/Cl, Na-Cl/HCO3, and HCO3-Na. Dominant ions are Na, Cl, and SO4. Measured electrical conductivity reaches values as high as 132,000 µS/cm. Water chemistry modifying processes include halite, gypsum, and carbonate dissolution; ion exchange; inter-HU water mixing; and evapo-concentration. δ18O-δD and EC-δ18O suggest the existence of subsurface flow sectors. In the south, shallow and medium depth groundwater flows respond to the current circulation of the SJRM. Recharge occurs in the sub-Andean Ranges and point discharges, at the western lakes and some lakes of the Golondrina-Calchaquí system. Precipitation recharges shallow flows locally in the north, center, and east. Extreme west HU2 and HU1 receive deep upward thermal flows through structural lineaments. Thus, the Otumpa Hills morpho-structure would be a barrier to shallow HU1 flow, though not to deep regional HU2 and HU4 flows. Regional groundwater flow is from NW to SE and both local and regional flows would discharge in the Paraná River. The new conceptual model developed helps to further understand the groundwater system of a large plain in South America.

Control of pyrethroid-resistant populations of Triatoma infestans, the main vector of Trypanosoma cruzi, by treating dogs with fluralaner in the Argentine Chaco.

We assessed whether fluralaner administered to outbred healthy dogs reduced or supressed site infestation and abundance of pyrethroid-resistant populations of Triatoma infestans Klug (Heteroptera: Reduviidae). We conducted a placebo-controlled before-and-after efficacy trial in 28 infested sites in Castelli (Argentine Chaco) over 10 months. All 72 dogs initially present received either an oral dose of fluralaner (treated group) or placebo (control group) at month 0 posttreatment (MPT). Preliminary results justified treating all 38 control-house dogs with fluralaner 1 month later, and 71 of 78 existing dogs at 7 MPT. Site-level infestation and triatomine abundance were evaluated using timed manual searches with a dislodging aerosol. In the fluralaner-treated group, infestation dropped significantly from 100% at baseline to 19% over 6-10 MPT whereas mean abundance fell highly significantly from 5.5 to 0.8-0.9 triatomines per unit effort. In the placebo group, site infestation and mean abundance remained stable between 0 and 1 MPT, and strongly declined after fluralaner administration from 13.0-14.7 - triatomines at 0-1 MPT to 4.0-4.2 over 6-10 MPT. Only one of 81 noninfested sites before fluralaner treatment became infested subsequently. Fluralaner significantly reduced the site-level infestation and abundance of pyrethroid-resistant T. infestans and should be tested more widely in Phase III efficacy trials.

A comparative wordlist for the languages of The Gran Chaco, South America.

Home to more than twenty indigenous languages belonging to six linguistic families, the Gran Chaco has raised the interest of many linguists from different backgrounds. While some have focused on finding deeper genetic relations between different language groups, others have looked into similarities from the perspective of areal linguistics. In order to contribute to further research of areal and genetic features among these languages, we have compiled a comparative wordlist consisting of translational equivalents for 326 concepts - representing basic and ethnobiological vocabulary - for 26 language varieties. Since the data were standardized in various ways, they can be analyzed both quantitatively and qualitatively. In order to illustrate this in detail, we have carried out an initial computer-assisted analysis of parts of the data by searching for shared lexicosemantic patterns resulting from structural rather than direct borrowings.

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

BACKGROUND: The 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. METHODS: The 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. RESULTS: Over 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. CONCLUSIONS: The 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.

Centre-periphery approaches based on geography, ecology and historical climate stability: what explains the variation in morphological traits of Bulnesia sarmientoi?

BACKGROUND AND AIMS: The centre-periphery hypothesis posits that higher species performance is expected in geographic and ecological centres rather than in peripheral populations. However, this is not the commonly found pattern; therefore, alternative approaches, including the historical dimension of species geographical ranges, should be explored. Morphological functional traits are fundamental determinants of species performance, commonly related to environmental stability and productivity. We tested whether or not historical processes may have shaped variations in tree and leaf traits of the Chaco tree Bulnesia sarmientoi. METHODS: Morphological variation patterns were analysed from three centre-periphery approaches: geographical, ecological and historical. Tree (stem and canopy) and leaf (leaf size and specific leaf area) traits were measured in 24 populations across the species range. A principal component analysis was performed on morphological traits to obtain synthetic variables. Linear mixed-effects models were used to test which of the implemented centre-periphery approaches significantly explained trait spatial patterns. KEY RESULTS: The patterns retrieved from the three centre-periphery approaches were not concordant. The historical approach revealed that trees were shorter in centre populations than in the periphery. Significant differences in leaf traits were observed between the geographical centre and the periphery, mainly due to low specific leaf area values towards the geographical centre. We did not find any pattern associated with the ecological centre-periphery approach. CONCLUSIONS: The decoupled response between leaf and tree traits suggests that these sets of traits respond differently to processes occurring at different times. The geographical and historical approaches showed centres with extreme environments in relation to their respective peripheries, but the historical centre has also been a climatically stable area since the Last Glacial Maximum. The historical approach allowed for the recovery of historical processes underlying variation in tree traits, highlighting that centre-periphery delimitations should be based on a multi-approach framework.

How do habitat amount and habitat fragmentation drive time-delayed responses of biodiversity to land-use change?

Land-use change is a root cause of the extinction crisis, but links between habitat change and biodiversity loss are not fully understood. While there is evidence that habitat loss is an important extinction driver, the relevance of habitat fragmentation remains debated. Moreover, while time delays of biodiversity responses to habitat transformation are well-documented, time-delayed effects have been ignored in the habitat loss versus fragmentation debate. Here, using a hierarchical Bayesian multi-species occupancy framework, we systematically tested for time-delayed responses of bird and mammal communities to habitat loss and to habitat fragmentation. We focused on the Argentine Chaco, where deforestation has been widespread recently. We used an extensive field dataset on birds and mammals, along with a time series of annual woodland maps from 1985 to 2016 covering recent and historical habitat transformations. Contemporary habitat amount explained bird and mammal occupancy better than past habitat amount. However, occupancy was affected more by the past rather than recent fragmentation, indicating a time-delayed response to fragmentation. Considering past landscape patterns is therefore crucial for understanding current biodiversity patterns. Not accounting for land-use history ignores the possibility of extinction debt and can thus obscure impacts of fragmentation, potentially explaining contrasting findings of habitat loss versus fragmentation studies.

Genetic structure of deltamethrin-resistant populations of Triatoma infestans (Hemiptera: Reduviidae) in the Gran Chaco.

The genetic structure of natural populations offers insight into the complexities of their dynamics, information that can be relevant to vector control strategies. Microsatellites are useful neutral markers to investigate the genetic structure and gene flow in Triatoma infestans, one of the main vectors of Chagas disease in South America. Recently, a heterogeneous pyrethroid-resistant hotspot was found in the Argentine Gran Chaco, characterized by the highest levels of deltamethrin resistance found at the present time. We applied population genetics analyses to microsatellite and village data and search for associations between the genetic variability and the heterogeneous toxicological pattern previously found. We genotyped 10 microsatellite loci in 67 T. infestans from 6 villages with no, low, and high pyrethroid resistance. The most genetically diverse populations were those susceptible or with low values of resistance. In contrast, high-resistance populations had lower herozygosity and some monomorphic loci. A negative association was found between variability and resistant ratios. Global and pairwise FSTs indicated significant differentiation between populations. The only susceptible population was discriminated in all the performed studies. Low-resistance populations were also differentiated by a discriminant analysis of principal components (DAPC) and were composed mostly by the same two genetic clusters according to STRUCTURE Bayesian algorithm. Individuals from the high-resistance populations were overlapped in the DAPC and shared significant proportions of a genetic cluster. These observations suggest that the resistant populations might have a common origin, although more genetic markers and samples are required to test this hypothesis more rigorously.

Urbanisation, risk stratification and house infestation with a major vector of Chagas disease in an endemic municipality of the Argentine Chaco.

BACKGROUND: The occurrence of the major vectors of Chagas disease has historically been linked to poor rural housing, but urban or peri-urban infestations are increasingly being reported. We evaluated a simple risk index to detect houses infested with Triatoma infestans and tested whether house infestation and vector abundance increased across the urban-to-rural gradient in Avia Terai, an endemic municipality of the Argentine Chaco; whether the association between infestation and selected ecological determinants varied across the gradient; and whether urban and peri-urban infestations were associated with population settlement history. METHODS: We conducted a screening survey of house infestation in 2296 urban, peri-urban and rural dwellings to identify high-risk houses based on a simple index, and then searched for triatomines in all high-risk houses and in a systematic sample of low-risk houses. RESULTS: The risk index had maximum sensitivity and negative predictive value, and low specificity. The combined number of infested houses in peri-urban and urban areas equalled that in rural areas. House infestation prevalence was 4.5%, 22.7% and 42.4% across the gradient, and paralleled the increasing trend in the frequency of domestic animals and peridomestic structures. Multiple logistic regression analysis showed that house infestation was positively and significantly associated with the availability of poultry and bug refuges in walls, and was negatively associated with domestic insecticide use. Several pieces of evidence, including absence of spatial aggregation of house infestation, support that T. infestans has been a long-established occupant of urban, peri-urban and rural settings in Avia Terai. CONCLUSIONS: An integrated vector management strategy targeting chicken coops and good husbandry practices may provide more cost-effective returns to insecticide-based vector elimination efforts.

Genomic diversity of the human pathogen Paracoccidioides across the South American continent.

Paracoccidioidomycosis (PCM) is a life-threatening systemic mycosis widely reported in the Gran Chaco ecosystem. The disease is caused by different species from the genus Paracoccidioides, which are all endemic to South and Central America. Here, we sequenced and analyzed 31 isolates of Paracoccidioides across South America, with particular focus on isolates from Argentina and Paraguay. The de novo sequenced isolates were compared with publicly available genomes. Phylogenetics and population genomics revealed that PCM in Argentina and Paraguay is caused by three distinct Paracoccidioides genotypes, P. brasiliensis (S1a and S1b) and P. restrepiensis (PS3). P. brasiliensis S1a isolates from Argentina are frequently associated with chronic forms of the disease. Our results suggest the existence of extensive molecular polymorphism among Paracoccidioides species, and provide a framework to begin to dissect the connection between genotypic differences in the pathogen and the clinical outcomes of the disease.

[Seroprevalence of Chagas´Disease in older than 14 years old in rural Chaco areas of Santa Fe Province.] / Seroprevalencia de Chagas en mayores de 14 años de áreas rurales del Chaco Santafesino.

Introduction: Chagas´Disease (CD) is endemic en Chaco Región. It is unknown the seroprevalence in population older than 14 years old from rural Chaco areas of Santa Fe Province. This study aimed to determine the seroprevalence of and socio-environmental factors associated with CD in inhabitants >14 years old of rural Chaco areas of Santa Fe, Argentina. Methods: A cross-sectional study was conducted between 2010 and 2015, in people over 14 years old, in the rural districts of the Chaco region, in the North of Santa Fe Province, Argentina. Blood serology for Trypanosoma cruzi antibodies based on two serological tests, and a third in case of discordance, were analized. Semi-structured survey was administered. Association between CD and socio-environmental variables were analyzed using prevalence ratios with 95% confidence intervals. Results: A total of 749 individual were analyzed, with an average of 29.5 years. The seroprevalence was 24.70% (26.69% in women and 20.26% in men). Socio-environmental variables showed association with Trypanosoma cruzi seropositive. The seroprevalence was 7.83 times higher in the children of mothers who had not reached secondary education. Conclusions: Chaco region of Santa Fe is endemic for CD, as well as other provinces of the Region. The low level of education is the more important conditioning for this endemic disease.

Introducción: Introducción. La Enfermedad de Chagas (ECh) es endémica en la Región del Chaco. Se desconoce su seroprevalencia en mayores de 14 años de áreas rurales del Chaco Santafesino. El objetivo del trabajo fue determinar la seroprevalencia de ECh en mayores de 14 años de áreas rurales del Chaco Santafesino, Argentina, y su asociación con factores de riesgo epidemiológico. Métodos: Se realizó un estudio transversal entre 2010 y 2015, en personas mayores de 14 años, los distritos rurales de la región del Chaco, en el Norte de la Provincia de Santa Fe, Argentina. Se determinó la prevalencia de anticuerpos contra Trypanosoma cruzi mediante dos pruebas serológicas, realizando una tercera en caso de discordancia. Se realizaron encuestas semiestructuradas sobre variables socioambientales. Se analizó la asociación entre ECh y variables socioambientales mediante la razón de prevalencias con un intervalo de confianza del 95%. Resultados: Se estudió una muestra de 749 personas, con una media de edad de 29,5 años. La seroprevalencia fue de 24,70% (26,69% en mujeres y 20,26% en hombres). Se halló asociación estadísticamente significativa entre las variables socioambientales y la seroprevalencia. La seroprevalencia fue 7,83 veces mayor en los hijos de madres que no habían alcanzado la educación secundaria. Conclusiones: La región del Chaco Santafesino es endémica para Chagas, al igual que otras provincias de la Región. El bajo nivel de instrucción materno es el condicionante más importante para esta endemia

Modelling the association between deltamethrin resistance in Triatoma infestans populations of the Argentinian Gran Chaco region with environmental factors.

In Latin America, Triatoma infestans is the main vector of the protozoan Trypanosoma cruzi, causal agent of Chagas disease. This blood-sucking triatomine is widely distributed in the Gran Chaco ecoregion, where chemical control has failed because of the evolution of resistance to pyrethroid insecticides. Recently, we described a deltamethrin high resistant focus in Güemes Department (Chaco province) characterized by susceptible populations, populations with low resistance (without field control failures) and some of the populations with the highest resistance level detected. This toxicological heterogeneity could be a result of non-homogenous insecticide pressure and be influenced by environmental factors. The present study evaluated the association of deltamethrin resistance ratios (RR50s) of T. infestans populations with explanatory variables extracted from the WorldClim dataset and constructed from information of National Chagas Program actions during 2005-2015. Control actions were distributed throughout the analyzed period, representing a homogeneous selective pressure. The average percentage of total positive houses was 33.66%. Models that included temperature and precipitation indicators presented 65% explanation. When village size variables where added, the explanatory power reached 70%. This observational result suggests that the climate may favor directly or indirectly the development/selection for resistance, representing a valuable tool to understand the occurrence of resistance that could increase the Chagas disease in the Gran Chaco.

Medicines in the forest: Ethnobotany of wild medicinal plants in the pharmacopeia of the Wichí people of Salta province (Argentina).

ETHNOPHARMACOLOGICAL RELEVANCE: This article presents the results of a study on wild plant pharmacopeia and medical ethnobotany of the Wichí people of the South American Gran Chaco region, where native forest still persist. Few previous works on the former subjects exist, with only partial information. Traditionally, shamans are in charge of healing serious diseases and wild plants are used for treating minor problems. Some ethnobotanists believe that much of the present pharmacopeia of native peoples of the Gran Chaco comes from the Criollos (local non-native people) and that medicinal plants and uses would have been much fewer in the past. AIMS OF THE STUDY: The study aims to: a) document the wild medicinal plants used by the Wichís and the associated ethnobotanical knowledge, b) discuss the use of medicinal plants in the current sanitary, epidemiological and ethnomedical context of the Wichís, and c) analyse the similarities between the medicinal plants and uses of the Wichís and those reported for the Criollos of the study area, for the We'enhayek (Wichís of Bolivia) and for other indigenous peoples of the Gran Chaco. All of them will help to answer a general research question: are medicinal wild plants of the Wichís present pharmacopoeia long-dated or are they relatively new adquisitions? MATERIALS AND METHODS: Original data were obtained between 2005 and 2017 from 51 informants through open and semi-structured interviews, participant observation, "walks-through-the-forest" technique and gathering of plant vouchers. Consensus of Use (CU) per species, use, ailment and use-category were calculated. Species and uses of the Wichís and those reported for other groups of the region were compared confronting the data, a similarity index (Sorensen) was calculated and a cluster analysis was carried out. An interpretative analysis of the results was performed. RESULTS: Original data consist of 408 applications for which 115 plants of 48 botanical families are used for treating 68 ailments or symptoms. Species are mainly used for treating prevalent health disorders in Wichí epidemiological context (skin and digestive disorders, fever, respiratory affections) and feminine issues. CONCLUSIONS: The similarity of the current Wichí pharmacopoeia with the other ethnic groups of the region seem to respond more to a geographical proximity than to cultural affinity. Much (but not all) of their pharmacopoeia seem to be novel, resulting from a permanent seek for solutions to both old and new health problems in the native forests. Many medicinal plants, but not specific uses, seem to come from the neighbouring Criollos, whilst traditional remedies seem to be simultaneously preserved. Hence, I propose that the ethnobotanical "diversification hypothesis", slightly modified, applies in the case of wild medicinal plants of the Wichís, as new wild medicines are being added to the old ones to fill therapeutic vacancies that for several sociocultural and historical reasons appear in their traditional pharmacopoeia. Altogether, results provide novel information of interest for ethnopharmacology, medical ethnobotany and related disciplines, expand the knowledge of Wichí pharmacopoeia and constitute a baseline for future diachronic and cross-cultural studies in the Gran Chaco region.

Comparative Study of 10 X-STR Markers in Populations of Northeast Argentina.

In northeast Argentina, different Amerindian communities share territory and history with settlers, mainly Europeans. Due to miscegenation, the current Argentinean population has a particular structure that can be described through X chromosome variation. The objectives of this study were to describe the variation of 10 X-chromosome short tandem repeats (X-STRs) in urban populations of the Argentinean regions known as Gran Chaco and Mesopotamia, report the forensic parameters of these STRs, and estimate the European and indigenous genetic components in these regions. Population and forensic parameters were estimated for 419 individuals from the analyzed populations, including two indigenous groups, Wichí and Mocoví, previously reported. Population structure was estimated through FST and RST distances and analysis of molecular variance. The indigenous American and European components were assessed with STRUCTURE. X-STRs showed a high level of genetic variability in urban and indigenous populations. Indigenous people of the Gran Chaco region showed significant differentiation from the urban samples (FST = 5.5%) and among themselves (FST = 5.3%). Genetic differentiation among urban groups was almost negligible, except that the population from Misión Nueva Pompeya differed from the rest of the city populations. Forensic parameters indicate that these X-STRs are useful as a complement to paternity tests. The set of 10 STRs could be a good tool for examining population differences.

High levels of human infection with Trypanosoma cruzi associated with the domestic density of infected vectors and hosts in a rural area of northeastern Argentina.

BACKGROUND: Insecticide spraying campaigns designed to suppress the principal vectors of the Chagas disease usually lack an active surveillance system that copes with house reinvasion. Following an insecticide campaign with no subsequent surveillance over a 12-year period, we implemented a longitudinal intervention programme including periodic surveys for Triatoma infestans, full-coverage house spraying with insecticides, and selective control in a well-defined rural area of the Argentinean Chaco inhabited by Creoles and one indigenous group (Qom). Here, we conducted a cross-sectional study and report the age-specific seroprevalence of human T. cruzi infection by group, and examine the association between human infection, the onset of the intervention, the relative density of infected domestic bugs, and the household number of infected people, dogs, or cats. RESULTS: The seroprevalence of infection among 691 residents examined was 39.8% and increased steadily with age, reaching 53-70% in those older than 20 years. The mean annual force of infection was 2.5 per 100 person-years (95% CI: 1.8-3.3%). Infection in children younger than 16 years born before the intervention programme was two to four times higher in houses with infected T. infestans than in houses without them and was six times higher when there were both infected dogs or cats and bugs than when they were absent. The model-averaged estimate of the intervention effect suggests that the odds of seropositivity were about nine times smaller for those born after the onset of the intervention than for those born before it, regardless of ethnic background, age, gender, household wealth, and cohabitation with T. cruzi-infected vectors or human hosts. Human infection was also closely associated with the baseline abundance of infected domestic triatomines and the number of infected cohabitants. Two of 43 children born after interventions were T. cruzi-seropositive; since their mothers were seropositive and both resided in apparently uninfested houses they were attributed to vertical transmission. Alternatively, these cases could be due to non-local vector-borne transmission. CONCLUSIONS: Our study reveals high levels of human infection with T. cruzi in the Argentinean Chaco, and the immediate impact of sustained vector surveillance and selective control actions on transmission.

Spatial analyzes of triatomine infestation indices and their association to the actions of a Chagas disease program and environmental variables during a 5-year intervention period.

Vector control of Chagas disease in the past decades has been mainly based on chemical control. Fundación Mundo Sano is implementing an Integral Chagas Program in a rural area of the Argentinean Gran Chaco Region since 2002. The objective of this study was to analyze both, temporal and spatial variation of infestation indices and their relation to the actions of the Program and environmental variables as land and vegetation cover changes, during a 5 year intervention period (2010-2014). Triatoma infestans infestation data from five rural localities from the Province of Santiago del Estero (Argentina) was analyzed in order to detect spatial aggregation. Differences in control effectiveness were observed between the peridomicile and intradomicile: infestation indices were higher in the peridomicile, recurrent infestation was present only in the peridomicile while low level infestation clusters were absent in the peridomicile. Cluster zones with low intradomestic infestation had larger proportions of bare soil and thin vegetation. In contrast, cluster zones with high intradomestic infestation had higher forest vegetation proportions and smaller cultivated area proportions. Spatial statistics analysis detected differences in cluster patterns between intra and peridomestic infestation suggesting that control actions should be based on geographical areas and not on political units. This work brings together different approaches to analyze infestation levels at the fine spatial scale, which could be used as a base for risk spatial stratification.