Malaria control: the power of integrated action
New strategies for malaria prevention and control are emphasizing ‘integrated vector management’ (IVM). This approach reinforces linkages between health and environment, optimizing benefits to both.
Integrated vector management is a dynamic and still-evolving field. IVM strategies are designed to achieve the greatest disease-control benefit in the most cost-effective manner, while minimizing negative impacts on ecosystems (e.g. depletion of biodiversity) and adverse side-effects on public health. Possible health risks range from acute exposures to pesticides and their residues to bio-accumulation of toxic chemicals, as well as the development of vector resistance to some widely-used pesticides and drugs.
A new WHO Global Strategic Framework for Integrated Vector Management defines IVM as a strategy to
. . . improve the efficacy, cost-effectiveness, ecological soundness and sustainability of disease vector control. IVM encourages a multi-disease control approach, integration with other disease control measures and the considered and systematic application of a range of interventions, often in combination and synergistically. (1)
Rather than relying on a single method of vector control (e.g. chemical spraying), IVM stresses the importance of first understanding the local vector ecology and local patterns of disease transmission, and then choosing the appropriate vector control tools from the range of options available.
These include environmental management strategies that can reduce or eliminate vector breeding grounds altogether, through improved design or operation of water resources development projects; and the use of biological controls (e.g. bacterial larvicides and larvivorous fish) that target and kill vector larvae without generating the ecological impacts of chemical use.
At the same time – when other measures are ineffective or not cost effective – IVM makes judicious use of chemical methods of vector control, such as indoor residual sprays, space spraying, and chemical larvicides and adulticides. These approaches reduce disease transmission by shortening or interrupting the lifespan of vectors (2,3).
IVM also provides a framework for improved personal protection/prevention strategies that combine the use of environmental management tools/physical barriers with chemical tools for new synergies, e.g. insecticide-treated nets (ITNs). Trials using insecticide-treated bednets in some malaria-endemic African countries have shown very substantial reductions in child and infant mortality (12). Finally, IVM supports more accessible and affordable disease diagnosis and treatment with effective anti-malarial drugs, within the framework of a multi-disease control approach.
IVM supports a process of ‘adaptive management’ through:
- periodic evaluation and reassessment of the ecological setting;
- monitoring of disease incidence and transmission; and
- health impact assessments of new developments to be undertaken by other sectors.
IVM therefore requires a fundamental restructuring of existing vector control programmes into a flexible, multi-pronged, multisectoral approach to vector-borne disease control that engages a range of government actors, communities, and agencies.
IVM is not a panacea for malaria – which is responsible for approximately 11% of the total disease burden in Africa (4) – or for vector-borne disease in general.
However, the large annual death toll from malaria, and the heavy burden of disease from other vector-borne diseases, the development of vector resistance to some widely-used insecticides and drugs, and the costs of developing new insecticides or insecticide-based control campaigns – all are indicators that a more multi-faceted approach to vector-borne disease is indeed warranted.
In many settings, the use of biological and environmental modification/management strategies – alongside or even in the place of insecticides – has yielded sustainable reductions in disease and transmission rates. The judicious use of insecticides, via careful and targeted application, also can preserve their long-term efficacy, slowing development of vector resistance.
In addition, a number of IVM field experiences have been documented as particularly cost effective in control of disease transmission. IVM strategies also have generated significant co-benefits to local economies in terms of development and growth – although more work is yet to be done, linking health and economic outcomes (5).
This brief provides examples of key experiences, which can provide guidance to policy-makers, together with an evaluation of their success in terms of health as well as economic costs and benefits (see Section 5, Cost-effectiveness of IVM).