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.

Host-feeding sources and habitats jointly affect wing developmental stability depending on sex in the major Chagas disease vector Triatoma infestans.

Fluctuating asymmetry (FA), a slight and random departure from bilateral symmetry that is normally distributed around a 0 mean, has been widely used to infer developmental instability. We investigated whether habitats (ecotopes) and host-feeding sources influenced wing FA of the hematophagous bug Triatoma infestans. Because bug populations occupying distinct habitats differed substantially and consistently in various aspects such as feeding rates, engorgement status and the proportion of gravid females, we predicted that bugs from more open peridomestic habitats (i.e., goat corrals) were more likely to exhibit higher FA than bugs from domiciles. We examined patterns of asymmetry and the amount of wing size and shape FA in 196 adult T. infestans collected across a gradient of habitat suitability and stability that decreased from domiciles, storerooms, kitchens, chicken coops, pig corrals, to goat corrals in a well-defined area of Figueroa, northwestern Argentina. The bugs had unmixed blood meals on human, chicken, pig and goat depending on the bug collection ecotope. We documented the occurrence of FA in wing shape for bugs fed on all host-feeding sources and in all ecotopes except for females from domiciles or fed on humans. FA indices for wing shape differed significantly among host-feeding sources, ecotopes and sexes. The patterns of wing asymmetry in females from domiciles and from goat corrals were significantly different; differences in male FA were congruent with evidence showing that they had higher mobility than females across habitats. The host-feeding sources and habitats of T. infestans affected wing developmental stability depending on sex.

Derivación biliopancreática de Larrad. Descripción de un modelo experimental en la rata / Larrad biliopancreatic diversion. Description of an rat experimental model

Objetivo. Validar un modelo experimental de derivación biliopancreática de Larrad (DBPL) y analizar las modificaciones ponderales y mortalidad en los animales operados alimentados con dieta estándar no suplementada. Material y metodo. Se utilizan 6 animales control y 10 operados, machos de la cepa Wistar. Se interviene al grupo de ratas operado con una adaptación de la técnica de Larrad en humanos: gastrectomía subcardial, canal biliopancreático corto creado a 5 cm del ángulo de Treitz y canal común a 5 cm de la válvula ileocecal. Tras un período de recuperación de 7 días las ratas se alimentan ad libitum con una dieta estándar no suplementada (sin proteínas, minerales o vitaminas), y se analiza el porcentaje de peso ganado o perdido. Resutados. Los animales control ganan peso progresivamente desde un 13,1 ± 2,4% en el día 7 hasta un 58 ± 9,2% en el día 63, momento en el que se los sacrificaba. Tras la DBPL la mortalidad es del 50% a los 25 ± 17,5 (rango, 14-56) días, sin diferencias significativas en el porcentaje de peso perdido entre los animales que sobrevivieron (­38,9 ± 14,2%) y los que fallecieron (­29 ± 5,6%; p = 0,192). El 80% de los animales que sobrevivieron perdieron peso progresivamente hasta alcanzar la máxima pérdida entre los 63 (­42,3 ± 8%) y 70 (­44,1 ± 9,7%) días. Un 20% de las ratas supervivientes perdieron peso hasta el día 35 y posteriormente recuperaron hasta un 7% el día del sacrificio (día 147). Conclusiones. El modelo experimental de DBPL es técnicamente factible. La mortalidad y el porcentaje de peso perdido no se encuentran directamente relacionados. El mecanismo de adaptación intestinal justificaría la recuperación de peso de los animales operados (AU)

Objective. To validate the experimental model of Larrad-biliopancreatic diversion (LBPD) and to analyze weight gain and mortality in rats fed with non­ supplemented diets. Material and method. Control (6) and experimental (10) male Wistar rats were used. The experimental group was operated on using the human LBPD adapted for rats: Subcardial gastrectomy, a short biliopancreatic channel created at 5 cm from Treitz angle and common channel at 5 cm from ileocecal valve. After surgery recovery (7 days) the rats were fed ab libitum with a standard non-supplemented diet (without proteins, minerals or vitamins). Percentage of weight lost or gained up to the end of the experiment was analyzed. Results. The control animals gained weight progressively from 13.1 ± 2.4% at day 7 to 58 ± 9.2% at day 63, when the animals were sacrificed. After LBPD, mortality was 50% at day 25 ± 17.5(range, 14-56), no significant differences in the percentage of weight lost being found between surviving (­38.9 ± 14.2%) and non-surviving rats (­29 ± 5.6%; p = 0.192). Of the surviving animals, 80% progressively lost weight reaching a maximum loss between day 63 (­42.3 ± 8%) and 70 (­44.1 ± 9.7%), and 20% lost weight until day 35 and gained over 7% of body weight until sacrifice (day 147). Conclusions. An experimental model of LBPD in rats is technically feasible. Both mortality and percentage weight loss are not directly related. The bowel adaptation mechanism could mediate the percentage of weight regain in operated rats (AU)