Vladimir Cruz-Chan

Bio: Vladimir Cruz-Chan is an academic researcher from Universidad Autónoma de Yucatán. The author has contributed to research in topics: Triatoma dimidiata & EcoHealth. The author has an hindex of 5, co-authored 5 publications receiving 144 citations.

Eco-Bio-Social Determinants for House Infestation by Non-domiciliated Triatoma dimidiata in the Yucatan Peninsula, Mexico

Abstract: Background: Chagas disease is a vector-borne disease of major importance in the Americas. Disease prevention is mostly limited to vector control. Integrated interventions targeting ecological, biological and social determinants of vector-borne diseases are increasingly used for improved control. Methodology/principal findings: We investigated key factors associated with transient house infestation by T. dimidiata in rural villages in Yucatan, Mexico, using a mixed modeling approach based on initial null-hypothesis testing followed by multimodel inference and averaging on data from 308 houses from three villages. We found that the presence of dogs, chickens and potential refuges, such as rock piles, in the peridomicile as well as the proximity of houses to vegetation at the periphery of the village and to public light sources are major risk factors for infestation. These factors explain most of the intra-village variations in infestation. Conclusions/significance: These results underline a process of infestation distinct from that of domiciliated triatomines and may be used for risk stratification of houses for both vector surveillance and control. Combined integrated vector interventions, informed by an Ecohealth perspective, should aim at targeting several of these factors to effectively reduce infestation and provide sustainable vector control

An innovative ecohealth intervention for Chagas disease vector control in Yucatan, Mexico

Abstract: Received 7 August 2014; revised 13 October 2014; accepted 13 October 2014Background:Non-domiciliated (intrusive) triatomine vectors remain a challenge for the sustainability ofChagas disease vector control as these triatomines are able to transiently (re-)infest houses. One of the best-characterizedexamplesisTriatomadimidiatafromtheYucatanpeninsula,Mexico,whereadultinsectsseasonallyinfest houses between March and July.Methods: We focused our study on three rural villages in the state of Yucatan, Mexico, in which we performeda situation analysis as a first step before the implementation of an ecohealth (ecosystem approach to health)vector control intervention.Results: The identification of the key determinants affecting the transient invasion of human dwellings byT. dimidiata was performed by exploring associations between bug presence and qualitative and quantitativevariables describing the ecological, biological and social context of the communities. We then used a participa-tory action research approach for implementation and evaluation of a control strategy based on window insectscreens to reduce house infestation by T. dimidiata.Conclusions: This ecohealth approach may represent a valuable alternative to vertically-organized insecticidespraying. Further evaluation may confirm that it is sustainable and provides effective control (in the sense oflimiting infestation of human dwellings and vector/human contacts) of intrusive triatomines in the region.Keywords: Chagas disease, Community participation, Triatoma dimidiata, Vector control

Non-randomized controlled trial of the long-term efficacy of an Ecohealth intervention against Chagas disease in Yucatan, Mexico.

Abstract: Non-domiciliated intrusive triatomine vectors are responsible for a low but significant transmission of Trypanosoma cruzi to humans. Their control is a challenge as insecticide spraying is of limited usefulness, and alternative strategies need to be developed for a sustainable control. We performed a non-randomized controlled trial of an Ecohealth intervention based on window insect screens and community participation to reduce house infestation by Triatoma dimidiata in two rural villages in Yucatan, Mexico. Efficacy of the intervention was measured over a three years follow-up period and entomological indicators showed that the proportion of triatomines found inside houses was significantly reduced in houses with insect screens, which effectively kept more bugs on the outside of houses. Using a previously developed model linking entomological data to the prevalence of infection in human, we predicted that the intervention would lead to a 32% reduction in yearly incidence and in the prevalence of T. cruzi infection. The cost for the coverage of all the windows of a house was of comparable magnitude to what families currently spend on various domestic insecticide, and most screens were still in good conditions after three years. In conclusion, the Ecohealth approach proposed here is effective for the long-term and sustainable control of intrusive T. dimidiata vectors in the Yucatan peninsula, Mexico. This strategy may also be easily adapted to other intrusive triatomine species as well as other regions/countries with comparable eco-epidemiological settings, and would be an excellent component of a larger integrated program for the control of a variety of other vector-borne diseases, bringing additional benefits to the communities. Our results should encourage a further scaling-up of our implementation strategy in additional villages in the region.

Una intervención innovadora de ecosalud para el control vectorial de la enfermedad de Chagas en Yucatán, México

Abstract: Introduccion. Los triatominos no-domiciliados (intrusivos), siguen siendo un desafio para el control sostenido de los vectores de la enfermedad de Chagas, debido a que estos tienen la capacidad de (re-)infestar las casas de forma transitoria. Uno de los ejemplos mejor caracterizado es el de Triatoma dimidiata en la peninsula de Yucatan, Mexico, donde los insectos adultos infestan las casas de forma estacional entre marzo y julio Metodos. Enfocamos nuestro estudio en 3 pueblos, realizando inicialmente un analisis de la situacion antes de implementar una intervencion de control vectorial con un enfoque de ecosalud (enfoque ecosistemico aplicado a la salud). Resultados. La identificacion de los determinantes claves que influyen sobre la infestacion estacional de las casas por T. dimidiata fue realizada explorando asociaciones entre la presencia de chinches y variables cualitativas y cuantitativas que describen el contexto ecologico, biologico y social de las comunidades. Posteriormente, utilizamos un abordaje de investigacion-accion participativa para la implementacion y evaluacion de una estrategia de control basada en el uso de mosquiteros para reducir la infestacion de las casas por T. dimidiata. Conclusiones. Este enfoque de ecosalud parece ser una alternativa valiosa al rociado de insecticidas organizado de forma vertical. Una evaluacion mas profunda deberia confirmar que esta intervencion es sostenible y proporciona un control efectivo (en el sentido de limitar la infestacion de las casas y los contactos vector/humano) de los triatominos intrusivos en la region.

사회사업에서의 Participatory Action Research(PAR)와 Action Research(AR) 모델 적용 필요성에 관한 연구

Abstract: 사회사업 조사연구는 복잡하고 다양한 인간의 욕구와 문제들을 해결하고 예측하기 위하여 과학적 방법론을 적극 활용하여 왔다. 과학적 방법론은 인간행동의 기준을 설정하고 결과를 제시하는데 객관성을 제공한다는 이유로 선호되고 있다. 그러나 이러한 과학적 방법론을 사회사업실천영역에서 사용하는데 있어서 간과해서 안 될 점은 클라이언트를 중심에 놓고 조사연구를 실행할 수 있어야 한다는 것이다. 즉, 개입을 계량화하는데 초점을 두지 않고 클라이언트를 중심에 두고 역량 강화할 수 있는 방법이 필요한 것이다. 이러한 맥락에서 본 연구는 사회사업 본연의 가치인 클라이언트 중심의 조사연구 접근과 이론과 실천의 간극을 메우는 하나의 교량으로서 실행연구(AR: action research)와 참여적 실행연구(PAR: participatory action research)의 개념과 과정을 소개하고 한국 사회사업실천에의 적용가능성을 모색하였다. AR과 PAR의 개념과 역사, 실행과정을 분석하고 사회사업실천에의 필요성과 적용점을 분석해본 결과, 필요성에 있어서는 실천현장에서의 적용용이성, 지역사회기반의 일반주의 실천접근과의 적합성, 조사연구와 실천의 통합, AR기술의 실천기술로서의 활용성 등으로 나타났다. 적용상의 이점으로는 클라이언트 문제와 욕구에 대한 보다 깊은 이해, 다각적인 맥락에 의거한 해결방법 모색, 조사자 곧 실천가 자신의 반성과 성장, 임파워먼트 실행의 촉매제로서의 기능, 조사연구의 확대가능성, 지역사회기반의 조사연구 확대, 효과적인 사회복지 조직관리에 있어서의 적용 등인 것으로 나타났다. 마지막으로 한국 현장에 AR을 도입하기 위해서 유의할 점으로 조사연구자로서의 실천가의 역량강화, 공동협력연구의 필요, 현장과 실천중심 연구를 강조하는 인센티브 제공, 구체적인 액션리서치의 한국형 모델 구축 등 4개의 과제를 제언하였다.

Chagas Disease in the United States: a Public Health Approach.

Abstract: Trypanosoma cruzi is the etiological agent of Chagas disease, usually transmitted by triatomine vectors. An estimated 20 to 30% of infected individuals develop potentially lethal cardiac or gastrointestinal disease. Sylvatic transmission cycles exist in the southern United States, involving 11 triatomine vector species and infected mammals such as rodents, opossums, and dogs. Nevertheless, imported chronic T. cruzi infections in migrants from Latin America vastly outnumber locally acquired human cases. Benznidazole is now FDA approved, and clinical and public health efforts are under way by researchers and health departments in a number of states. Making progress will require efforts to improve awareness among providers and patients, data on diagnostic test performance and expanded availability of confirmatory testing, and evidence-based strategies to improve access to appropriate management of Chagas disease in the United States.

Intrusive versus domiciliated triatomines and the challenge of adapting vector control practices against Chagas disease

Abstract: Chagas disease prevention remains mostly based on triatomine vector control to reduce or eliminate house infestation with these bugs. The level of adaptation of triatomines to human housing is a key part of vector competence and needs to be precisely evaluated to allow for the design of effective vector control strategies. In this review, we examine how the domiciliation/intrusion level of different triatomine species/populations has been defined and measured and discuss how these concepts may be improved for a better understanding of their ecology and evolution, as well as for the design of more effective control strategies against a large variety of triatomine species. We suggest that a major limitation of current criteria for classifying triatomines into sylvatic, intrusive, domiciliary and domestic species is that these are essentially qualitative and do not rely on quantitative variables measuring population sustainability and fitness in their different habitats. However, such assessments may be derived from further analysis and modelling of field data. Such approaches can shed new light on the domiciliation process of triatomines and may represent a key tool for decision-making and the design of vector control interventions.

Detailed ecological associations of triatomines revealed by metabarcoding and next-generation sequencing: implications for triatomine behavior and Trypanosoma cruzi transmission cycles.

Abstract: Trypanosoma cruzi is the agent of Chagas disease, transmitted by hematophagous triatomine vectors. Establishing transmission cycles is key to understand the epidemiology of the disease, but integrative assessments of ecological interactions shaping parasite transmission are still limited. Current approaches also lack sensitivity to assess the full extent of this ecological diversity. Here we developed a metabarcoding approach based on next-generation sequencing to identify triatomine gut microbiome, vertebrate feeding hosts, and parasite diversity and their potential interactions. We detected a dynamic microbiome in Triatoma dimidiata, including 23 bacterial orders, which differed according to blood sources. Fourteen vertebrate species served as blood sources, corresponding to domestic, synantropic and sylvatic species, although four (human, dog, cow and mice) accounted for over 50% of blood sources. Importantly, bugs fed on multiple hosts, with up to 11 hosts identified per bug, indicating very frequent host-switching. A high clonal diversity of T. cruzi was detected, with up to 20 haplotypes per bug. This analysis provided much greater sensitivity to detect multiple blood meals and multiclonal infections with T. cruzi, which should be taken into account to develop transmission networks, and characterize the risk for human infection, eventually leading to a better control of disease transmission.