http://idl-bnc.idrc.ca:80/dspace/handle/10625/35554 Wed, 19 Jun 2013 09:18:58 GMT 2013-06-19T09:18:58Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/50957 Title: Origins of house reinfestation with Triatoma infestans after insecticide spraying in the Argentine Chaco using wing geometric morphometry Authors: Gaspe, M. Sol; Gurevitz, Juan M.; Gürtler, Ricardo E.; Dujardin, Jean-Pierre Abstract: Identifying the origins of insect vectors collected after community-wide residual insecticide applications 24 is a relevant challenge in the Gran Chaco region where the main vector of Chagas disease Triatoma infe- 25 stans usually reinfests human dwellings. Wing geometric morphometry was used to compare the right 26 wings of 63 males and 54 females collected at 4 months post-spraying (MPS) with those from 165 males 27 and 111 females collected before full-coverage spraying with pyrethroids in a well-defined rural area in 28 Northeastern Argentina. Male and female wing centroid size resulted significantly larger at 4 MPS than 29 before interventions, but no significant changes in shape were detected. Metric disparity (variance of 30 shape) varied significantly in males but not in females. Using shape variables, a relatively large fraction 31 of post-spraying males (70%) and females (54%) could not be differentiated from those collected at the 32 same source house or at the nearest infested house before interventions. Bugs collected at 4 and 33 8 MPS in a persistently infested house were mainly assigned to the source house. These results support 34 the hypothesis of persistent bug populations that survived the insecticide application at local spatial 35 scales, and are consistent with the occurrence of vector control failures most likely related to moderate 36 pyrethroid resistance. Wing geometric morphometry is a useful tool for identifying sources of reinfesta- 37 tion, but it is limited by the spatial structure found in the reference populations. Combined with field and 38 genetic data, this approach may contribute to the understanding of the reinfestation process and 39 improvement of vector control strategies. Description: Article in press Mon, 25 Mar 2013 00:00:00 GMT http://idl-bnc.idrc.ca:80/dspace/handle/10625/50957 2013-03-25T00:00:00Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/50956 Title: Spatial heterogeneity and risk maps of community infestation by Triatoma infestans in rural Northwestern Argentina Authors: Vazquez-Prokopec, Gonzalo M.; Spillmann, Cynthia; Zaidenberg, Mario; Gürtler, Ricardo E.; Kitron, Uriel Abstract: Background: Fifty years of residual insecticide spraying to control Triatoma infestans in the Gran Chaco region of northern Argentina, Paraguay and Bolivia shows that vertically coordinated interventions aiming at full coverage have limited effects and are unsustainable. We quantified the spatial distribution of T. infestans domestic infestation at the district level, identified environmental factors associated with high infestation and then explored the usefulness of risk maps for the spatial stratification of interventions. Methods and Findings: We performed spatial analyses of house infestation data collected by the National Chagas Service in Moreno Department, northern Argentina (1999–2002). Clusters of high domestic infestation occurred in the southwestern extreme of the district. A multi-model selection approach showed that domestic infestation clustered in areas of low elevation, with few farmlands, high density of rural houses, high mean maximum land surface temperature, large NDVI, and high percentage of degraded and deforested lands. The best model classified 98.4% of the communities in the training dataset (sensitivity, 93.3%; specificity, 95.4%). The risk map evidenced that the high-risk area only encompassed 16% of the district. By building a network-based transportation model we assessed the operational costs of spatially contiguous and spatially targeted interventions. Targeting clusters of high infestation would have reached ,80% of all communities slated for full-coverage insecticide spraying, reducing in half the total time and economic cost incurred by a spatially contiguous strategy. Conclusions and Significance: In disperse rural areas where control programs can accomplish limited coverage, consideration of infestation hot spots can contribute to the design and execution of cost-effective interventions against Chagas disease vectors. If field validated, targeted vertical control in high risk areas and horizontal control in medium to low risk areas may provide both a logistically and economically feasible alternative to blanket vertical insecticide spraying when resources are limited. Tue, 14 Aug 2012 00:00:00 GMT http://idl-bnc.idrc.ca:80/dspace/handle/10625/50956 2012-08-14T00:00:00Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/50955 Title: Sylvatic transmission cycle of Trypanosoma cruzi in a rural area in the humid Chaco of Argentina Authors: Alvarado-Otegui, J.A.; Ceballos, L.A.; Orozco, M.M.; Enriquez, G.F.; Cardinal, M.V. Abstract: Little is known about the sylvatic transmission cycle of Trypanosoma cruzi in the Gran Chaco ecoregion. We conducted surveys to identify the main sylvatic hosts of T. cruzi, parasite discrete typing units and vector species involved in Pampa del Indio, a rural area in the humid Argentinean Chaco. A total of 44 mammals from 14 species were captured and examined for infection by xenodiagnosis and polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNAPCR). Ten (22.7%) mammals were positive by xenodiagnosis or kDNA-PCR. Four of 11 (36%) Didelphis albiventris (white-eared opossums) and six of nine (67%) Dasypus novemcinctus (nine-banded armadillos) were positive by xenodiagnosis and or kDNA-PCR. Rodents, other armadillo species, felids, crab-eating raccoons, hares and rabbits were not infected. Positive animals were highly infectious to the bugs that fed upon them as determined by xenodiagnosis. All positive opossums were infected with T. cruzi I and all positive nine-banded armadillos with T. cruzi III. Extensive searches in sylvatic habitats using 718 Noireau trap-nights only yielded Triatoma sordida whereas no bug was collected in 26 light-trap nights. Four armadillos or opossums fitted with a spool-and-line device were successfully tracked to their refuges; only one Panstrongylus geniculatus was found in an armadillo burrow. No sylvatic triatomine was infected with T. cruzi by microscopical examination or kDNA-PCR. Our results indicate that two independent sylvatic transmission cycles of T. cruzi occur in the humid Chaco. The putative vectors of both cycles need to be identified conclusively. Description: Article in press Tue, 26 Jun 2012 00:00:00 GMT http://idl-bnc.idrc.ca:80/dspace/handle/10625/50955 2012-06-26T00:00:00Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/50954 Title: Discrete typing units of Trypanosoma cruzi identified in rural dogs and cats in the humid Argentinean Chaco Authors: Enriquez, G.F.; Cardinal, M.V.; Orozco, M.M.; Lanati, L.; Schijman, A.G.; Gürtler, R.E. Abstract: The discrete typing units (DTUs) of Trypanosoma cruzi that infect domestic dogs and cats have rarely been studied.With this purpose we conducted a cross-sectional xenodiagnostic survey of dog and cat populations residing in 2 infested rural villages in Pampa del Indio, in the humid Argentine Chaco. Parasites were isolated by culture from 44 dogs and 12 cats with a positive xenodiagnosis. DTUs were identified from parasite culture samples using a strategy based on multiple polymerase-chain reactions. TcVI was identified in 37 of 44 dogs and in 10 of 12 cats, whereas TcV was identified in 5 dogs and in 2 cats –a new finding for cats. No mixed infections were detected. The occurrence of 2 dogs infected with TcIII – classically found in armadillos– suggests a probable link with the local sylvatic transmission cycle involving Dasypus novemcinctus armadillos and a potential risk of human infection with TcIII. Our study reinforces the importance of dogs and cats as domestic reservoir hosts and sources of various DTUs infecting humans, and suggests a link between dogs and the sylvatic transmission cycle of TcIII. Mon, 01 Oct 2012 00:00:00 GMT http://idl-bnc.idrc.ca:80/dspace/handle/10625/50954 2012-10-01T00:00:00Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/50953 Title: Detection of Trypanosoma cruzi infection in naturally infected dogs and cats using serological, parasitological and molecular methods Authors: Enriquez, G.F.; Cardinal, M.V.; Orozco, M.M.; Schijman, A.G.; Gürtler, R.E. Abstract: Domestic dogs and cats are major domestic reservoir hosts of Trypanosoma cruzi and a risk factor for parasite transmission. In this study we assessed the relative performance of a polymerase chain reaction assay targeted to minicircle DNA (kDNA-PCR) in reference to conventional serological tests, a rapid dipstick test and xenodiagnosis to detect T. cruzi infection in dogs and cats from an endemic rural area in northeastern Argentina. A total of 43 dogs and 13 cats seropositive for T. cruzi by an immunosorbent assay (ELISA) and an indirect hemagglutination assay (IHA), which had been examined by xenodiagnosis, were also tested by kDNA-PCR. kDNA-PCR was nearly as sensitive as xenodiagnosis for detecting T. cruzi-infectious dogs and cats. kDNA-PCR was slightly more sensitive than xenodiagnosis in seropositive dogs (91% versus 86%, respectively) and cats (77% against 54%, respectively), but failed to detect all of the seropositive individuals. ELISA and IHA detected all xenodiagnosis-positive dogs and both outcomes largely agreed (kappa coefficient, κ = 0.92), whereas both assays failed to detect all of the xenodiagnosis-positive cats and their agreement was moderate (κ = 0.68). In dogs, the sensitivity of the dipstick test was 95% and agreed closely with the outcome of conventional serological tests (κ = 0.82). The high sensitivity of kDNA-PCR to detect T. cruzi infections in naturally infected dogs and cats supports its application as a diagnostic tool complementary to serology and may replace the use of xenodiagnosis or hemoculture. Sun, 03 Mar 2013 00:00:00 GMT http://idl-bnc.idrc.ca:80/dspace/handle/10625/50953 2013-03-03T00:00:00Z