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

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.

Pupal productivity of dengue vectors in Kolkata, India: implications for vector management.

Background & objectives: Entomological surveillance of the dengue vectors using pupal productivity as indicators can be helpful in effective management. On this basis, an assessment was made on the relative importance of the larval habitats of Aedes mosquitoes in Kolkata, an endemic zone for dengue in West Bengal, India. Methods: Monthly collection of larvae and pupae of Aedes from larval habitats categorized as earthen, plastic and porcelain containers and tyres, was carried out from selected sites. Pupal weight was recorded and degree of sexual dimorphism was calculated. The data on pupal weight, sexual dimorphism and immature density were used for regression analysis. Results: The number of positive sites for each type of larval habitats varied with months and mosquito species. Based on mean density per month, the plastic containers were the most productive habitats and the tyres were least productive for both Aedes species. The pupal weight of both Ae. aegypti and Ae. albopictus varied with the relative density and type of larval habitats. Significant differences in pupal productivity, positive sites and the proportion of pupae were observed in the habitats. Species-specific differences in the degree of dimorphism were noted with the females being larger in size than males, irrespective of the habitats. Interpretation & conclusions: Pupal productivity of Aedes mosquitoes in Kolkata differed in terms of the type of the larval habitats with the immature density affecting the body size of the adults. This habitat-based study is a pioneer effort considering Kolkata and calls for a management plan for source reduction of these habitats to minimize Aedes mosquitoes and thus potential risk of dengue.

Global status of DDT and its alternatives for use in vector control to prevent disease: [review] / Estado global do DDT e suas alternativas para utilização no controle de vetores para prevenção de doenças: [revisão]

Neste artigo, revisei o estado do dicloro-difenil-tricloroetano (DDT) utilizado no controle de doenças causadas por vetores, e seus benefícios e riscos em relação às alternativas disponíveis. Dados atuais sobre o uso de DDT foram obtidos através de questionários e relatórios, assim como uma busca Scopus para resgatar artigos publicados. Quase 14 países utilizam DDT para controle de doenças, e diversos outros o estão reintroduzindo. A preocupação sobre o uso contínuo de DDT é abastecida por relatórios recentes dos altos níveis de exposição humana associada com a pulverização em recintos fechados, acumulando evidências sobre efeitos crônicos a saúde. Existem sinais de que mais vetores da malária estão se tornando resistentes à ação tóxica do DDT. Métodos químicos efetivos estão disponíveis como alternativas imediatas ao DDT, mas o desenvolvimento da resistência está diminuindo a eficácia das ferramentas de insetização. Métodos não químicos são potencialmente importantes, mas sua efetividade no programa necessita de estudos urgentes. O controle integrado de vetores fornece uma estrutura para o desenvolvimento e a implementação de tecnologias e estratégias efetivas como alternativas sustentáveis à dependência ao DDT.

In this article I reviewed the status of dichlorodiphenyltrichloroethane (DDT), used for disease vector control, and its benefits and risks in relation to the available alternatives. Contemporary data on DDT use were obtained from questionnaires and reports as well as a Scopus search to retrieve published articles. Nearly 14 countries use DDT for disease control, and several others are reintroducing DDT. Concerns about the continued use of DDT are fueled by recent reports of high levels of human exposure associated with indoor spraying amid accumulating evidence on chronic health effects. There are signs that more malaria vectors are becoming resistant to the toxic action of DDT. Effective chemical methods are available as immediate alternatives to DDT, but the development of resistance is undermining the efficacy of insecticidal tools. Nonchemical methods are potentially important, but their effectiveness at program level needs urgent study. To reduce reliance on DDT, support is needed for integrated and multipartner strategies of vector control. Integrated vector management provides a framework for developing and implementing effective technologies and strategies as sustainable alternatives to reliance on DDT.

Integrated Vector Management- A New Strategy for Vector-Borne Disease Control - / 国際保健医療

 Integrated Vector Management (IVM) is defined as "a rational decision-making process for the optimal use of resources for vector control". The approach seeks to improve the efficacy, cost-effectiveness, ecological soundness and sustainability of disease-vector control. The ultimate goal of IVM is to prevent the transmission of vector-borne diseases such as malaria, dengue, lymphatic filariasis, leishmaniasis, schistosomiasis and Chagas disease.<br> WHO promotes the principles of IVM as set out in the “Global strategic framework for integrated vector management”. It lists five key elements of IVM: capacity building; advocacy and social mobilization; legislation framework; evidence-based decision-making; and integrated approaches. This framework is in line with the global plan for 2008-2015 to combat neglected tropical diseases through delivery of multi-intervention packages, which also promotes the IVM approach. <br> In 2008, WHO produced the position statement on IVM to support the advancement of IVM as an important component of vector-borne disease control. The member states are invited to accelerate the development of national policies and strategies, while international organizations, donor agencies and other stakeholders are encouraged to support the capacity strengthening necessary for implementation of IVM. <br> In order to take the next step and to transform the framework and policies into actual implementation, the first IVM stakeholders meeting was held in Geneva in November 2009. The meeting developed a roadmap aimed at strengthening evidence-based decision-making for new initiatives and recommended the establishment of a partnership mechanism to facilitate effective information sharing and foster better collaboration with regards to the implementation of IVM.<br> This paper introduces the IVM position statement in Japanese language with the aim of disseminating the concept and approach of IVM in Japan.