Malaria control: the power of integrated action

Principles of integrated vector management

Integrated vector management is about better decision-making. Rather than relying upon blanket solutions, vector control managers – together with managers in health, agriculture, water resources, and land use – need to examine the local eco-setting of the disease vector and disease transmission patterns, and then systematically design and periodically update strategies and action plans. New scientific knowledge about the ecology and behaviour of mosquitoes and their natural predators has improved the precision of vector control methods in general, and can permit better use of more ‘environmentally friendly’ vector control methods in the IVM framework.

In particular, advances in geographical information systems (GIS) have contributed to more precise mapping of the distribution of mosquito species, their breeding areas, and disease transmission. These can be used to guide targeted control efforts, improve cost-effectiveness and minimize unwanted ecosystem disruption or damage (13,14). In addition, technical advances in knowledge about larval control have made the use of biological insecticides more practical and feasible today than in the past (15).

Choices about vector control are best considered with reference to a ‘hierarchy’ of interventions. This hierarchy follows the historic development of vector control methods and begins with environmental management strategies, which – if effective in the local setting – can yield the most sustained long-term benefits at the lowest cost.

Fig. 3 - Use of maps to predict current and future disease distributions
Fig. 3 - Use of maps to predict current and future disease distributions

Other methods – that offer higher impact, more partial, limited or shorter-term solutions – are then cumulatively added until the target or threshold set for reduction of disease transmission levels is met. This is a departure from the selective or targeted vector control approach – which maintains chemical interventions as its basis and therefore does not use the environmental, personal protection, and biological control methods to their full potential.

Use of multiple tools and strategies can impact the malaria transmission cycle along a series of vulnerable points in specific eco-settings, creating a more successful overall strategy. It should be remembered, however, that in most places where malaria thrives today – and under current conditions – reaching zero disease transmission rates is unlikely. Accordingly, IVM will be an ongoing activity.

Environmental management is a key element of IVM. Environmental management can include environmental modification, environmental manipulation, and strategies that reduce contacts between vectors and humans. [1]

  • Environmental modification usually involves capital-intensive investments in permanent infrastructure, such as better dam, water, and irrigation infrastructure design. Such modifications may either sustainably control or destroy vector habitats over the long term.
  • More time-limited environmental manipulation strategies involve recurrent activities, such as the periodic removal of aquatic weeds, or the removal of riverine vegetation to manipulate shade and sunlight conditions; alternating cycles of irrigation and dry farming; or maintenance of canal-lining to prevent seepage leading to the development of vector breeding pools.
  • A third type of environmental management strategy aims to reduce human–vector contacts through the strategic placement of settlements and housing, or better use of window screening. Originally, such strategies also included effective use of mosquito nets – until the increased popularity of insecticide-treated nets (ITNs) placed those devices into a category of their own.

IVM also aims to make effective use of biologically-based agents such as bacterial larvicides and larvivorous fish, which may 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 control methods. Chemical tools, including indoor residual sprays or space spraying, shorten or interrupt the lifespan of adult vectors, and thus reduce disease transmission rates (2,3). They remain particularly important in areas of intense disease transmission, where environmental management strategies alone cannot reduce vector densities sufficiently to actually make an impact on disease incidence.

In integrated vector management, vector control at the local ecosystem and community levels works in synergy with controls or prevention measures at the household and personal levels. For example, more frequent individual use of insecticide-treated nets has been viewed as vital to improved malaria prevention in many parts of Africa and Asia.

In addition, more than one disease can be targeted at a time. For instance, in Asia and in the Americas, improved screening of homes and water containers (sometimes with insecticide-treated nets) may help protect against dengue as well as malarial vectors.

Along with effective disease diagnosis and treatment, the careful monitoring of disease incidence is important in order to fine-tune and improve vector control strategies. Finally, community support and increased individual awareness are necessary to facilitate a more integrated approach to vector control/prevention and disease care/treatment measures, and to ensure their sustainability.