Dataset Information

Triatomine infestation in Guatemala: spatial assessment after two rounds of vector control.

ABSTRACT: In 2000, the Guatemalan Ministry of Health initiated a Chagas disease program to control Rhodnius prolixus and Triatoma dimidiata by periodic house spraying with pyrethroid insecticides to characterize infestation patterns and analyze the contribution of programmatic practices to these patterns. Spatial infestation patterns at three time points were identified using the Getis-Ord Gi*(d) test. Logistic regression was used to assess predictors of reinfestation after pyrethroid insecticide administration. Spatial analysis showed high and low clusters of infestation at three time points. After two rounds of spray, 178 communities persistently fell in high infestation clusters. A time lapse between rounds of vector control greater than 6 months was associated with 1.54 (95% confidence interval = 1.07-2.23) times increased odds of reinfestation after first spray, whereas a time lapse of greater than 1 year was associated with 2.66 (95% confidence interval = 1.85-3.83) times increased odds of reinfestation after first spray compared with localities where the time lapse was less than 180 days. The time lapse between rounds of vector control should remain under 1 year. Spatial analysis can guide targeted vector control efforts by enabling tracking of reinfestation hotspots and improved targeting of resources.

SUBMITTER: Manne J

PROVIDER: S-EPMC3284360 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Triatomine infestation in Guatemala: spatial assessment after two rounds of vector control.

Manne Jennifer J Nakagawa Jun J Yamagata Yoichi Y Goehler Alexander A Brownstein John S JS Castro Marcia C MC

The American journal of tropical medicine and hygiene 20120301 3

In 2000, the Guatemalan Ministry of Health initiated a Chagas disease program to control Rhodnius prolixus and Triatoma dimidiata by periodic house spraying with pyrethroid insecticides to characterize infestation patterns and analyze the contribution of programmatic practices to these patterns. Spatial infestation patterns at three time points were identified using the Getis-Ord Gi*(d) test. Logistic regression was used to assess predictors of reinfestation after pyrethroid insecticide administ ...[more]

PMID: 22403315

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Project description:BackgroundFailure to detect a disease agent or vector where it actually occurs constitutes a serious drawback in epidemiology. In the pervasive situation where no sampling technique is perfect, the explicit analytical treatment of detection failure becomes a key step in the estimation of epidemiological parameters. We illustrate this approach with a study of Attalea palm tree infestation by Rhodnius spp. (Triatominae), the most important vectors of Chagas disease (CD) in northern South America.Methodology/principal findingsThe probability of detecting triatomines in infested palms is estimated by repeatedly sampling each palm. This knowledge is used to derive an unbiased estimate of the biologically relevant probability of palm infestation. We combine maximum-likelihood analysis and information-theoretic model selection to test the relationships between environmental covariates and infestation of 298 Amazonian palm trees over three spatial scales: region within Amazonia, landscape, and individual palm. Palm infestation estimates are high (40-60%) across regions, and well above the observed infestation rate (24%). Detection probability is higher ( approximately 0.55 on average) in the richest-soil region than elsewhere ( approximately 0.08). Infestation estimates are similar in forest and rural areas, but lower in urban landscapes. Finally, individual palm covariates (accumulated organic matter and stem height) explain most of infestation rate variation.Conclusions/significanceIndividual palm attributes appear as key drivers of infestation, suggesting that CD surveillance must incorporate local-scale knowledge and that peridomestic palm tree management might help lower transmission risk. Vector populations are probably denser in rich-soil sub-regions, where CD prevalence tends to be higher; this suggests a target for research on broad-scale risk mapping. Landscape-scale effects indicate that palm triatomine populations can endure deforestation in rural areas, but become rarer in heavily disturbed urban settings. Our methodological approach has wide application in infectious disease research; by improving eco-epidemiological parameter estimation, it can also significantly strengthen vector surveillance-control strategies.

Project description:BACKGROUND:Improved access to health care and quality of services require integrated efforts and innovations, including community empowerment and participation in transformation processes. Chagas disease is a neglected tropical disease that is generally controlled by insecticide spraying. To achieve community empowerment in a health program, actions for social innovations may include: community-based research, interdisciplinary and intersectoral participation, community perception of direct benefits and participation in health or environmental improvements. The aim of this study was to describe and analyze the processes by which an interdisciplinary team, in collaboration with communities of Comapa, Guatemala, developed an effective solution to address the risk for Chagas disease. METHODS:A qualitative study involving interviews semi-structured and direct observation was conducted using a case study approach to describe and understand the community-based research and intervention process developed by researchers from the Laboratory of Applied Entomology and Parasitology of the Universidad de San Carlos of Guatemala (Laboratorio de Entomologia y Parasitologia Aplicada). Nine interviews were conducted with the investigators, innovators, members of the community in which the intervention had been implemented. NVivo software (version 12) was used for the emergent coding and analysis of the interviews. RESULTS:Processes of social transformation were evident within households, and the communities that transcended the mere improvement of walls and floors. New social dynamics that favored the household economy and conditions of hygiene and home care that positively impacted the health of the community. We describe how the integration of criteria of social innovation into a home improvement strategy for Chagas disease control, can generate processes of transformation in health by considering sociocultural conditions, encouraging dialogue between public health approaches and traditional practices. We identify and discuss processes for Social Innovations in Health and identify their potential in improving community health in Latin America. CONCLUSIONS:When social innovation criteria are included in a health control initiative, the community-based research and the interdisciplinary and intersectoral participation facilitate the implementation of the control strategy, the perceived benefits by the community and its empowerment to sustain and share the strategy. The case study provided understanding of the intersectoral and interdisciplinary dynamics in particular contexts, and documented the relevance of innovation criteria in health processes.

Project description:BackgroundAn estimated 2·5 billion people are at risk of dengue. Incidence of dengue is especially high in resource-constrained countries, where control relies mainly on insecticides targeted at larval or adult mosquitoes. We did epidemiological and economic assessments of different vector control strategies.MethodsWe developed a dynamic model of dengue transmission that assesses the evolution of insecticide resistance and immunity in the human population, thus allowing for long-term evolutionary and immunological effects of decreased dengue transmission. We measured the dengue health burden in terms of disability-adjusted life-years (DALYs) lost. We did a cost-effectiveness analysis of 43 insecticide-based vector control strategies, including strategies targeted at adult and larval stages, at varying efficacies (high-efficacy [90% mortality], medium-efficacy [60% mortality], and low-efficacy [30% mortality]) and yearly application frequencies (one to six applications). To assess the effect of parameter uncertainty on the results, we did a probabilistic sensitivity analysis and a threshold analysis.FindingsAll interventions caused the emergence of insecticide resistance, which, with the loss of herd immunity, will increase the magnitude of future dengue epidemics. In our model, one or more applications of high-efficacy larval control reduced dengue burden for up to 2 years, whereas three or more applications of adult vector control reduced dengue burden for up to 4 years. The incremental cost-effectiveness ratios of the strategies for two high-efficacy adult vector control applications per year was US$615 per DALY saved and for six high-efficacy adult vector control applications per year was $1267 per DALY saved. Sensitivity analysis showed that if the cost of adult control was more than 8·2 times the cost of larval control then all strategies based on adult control became dominated.InterpretationSix high-efficacy adult vector control applications per year has a cost-effectiveness ratio that will probably meet WHO's standard for a cost-effective or very cost-effective intervention. Year-round larval control can be counterproductive, exacerbating epidemics in later years because of evolution of insecticide resistance and loss of herd immunity. We suggest the reassessment of vector control policies that are based on larval control only.FundingThe Fulbright Programme, CAPES (Brazilian federal agency for post-graduate education), the Miriam Burnett trust, and the Notsew Orm Sands Foundation.

Dataset Information

Triatomine infestation in Guatemala: spatial assessment after two rounds of vector control.

Publications

Triatomine infestation in Guatemala: spatial assessment after two rounds of vector control.

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