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Integrated Vector Control

Read Chadwick Sikaala and Mark Hoppé describe how an integrated approach to vector control, looking at the wider system, can offer many advantages.
© University of Basel

Integrated Vector Control (IVC) and Integrated Vector Management (IVM), whilst having overlapping principles, are sometimes erroneously used interchangeably.

The WHO defines IVM as “A rational decision-making process for the optimal use of resources for vector control”. IVC, on the other hand, has a more general meaning, which can perhaps best be described as taking a holistic or systems approach to reducing the burden of vector-borne disease (VBD), and is the subject of this article.

An integrated system

The use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS) aren’t the only activities that are employed for the control of malaria mosquitoes, or which place a selection pressure on them for insecticide resistance development.

Other insecticide-based vector control activities may be employed alongside, or in place of, ITNs and IRS. For example: the use of larvicides to prevent mosquito larvae developing into adults; the use of space sprays or fogs to control adult mosquitoes; spatial repellents, which use volatile insecticides that repel or kill mosquitoes in a limited zone around the source.

Other approaches that are being developed, and show promise, include: Attractive Targeted Sugar Baits (ATSB), which provide a toxic sugar-based bait in a device that only mosquitoes can access; and eave tubes, which expose mosquitoes to an insecticide deposit when they try to enter a modified house.

One aspect of IVC is to integrate the use of such insecticide-based interventions to increase the overall impact of the programme. This may also have an IRM benefit if insecticides with different modes of action are used.

Non-insecticidal interventions

However, there are also interventions that don’t rely on insecticides that can impact mosquito numbers and their interaction with humans. For example, environmental modifications that minimise the water bodies that the larvae develop in. This could include draining or filling holes left in the ground after construction work, tyre tracks etc., careful water storage, minimising standing water in irrigated crops, or careful management of water in paddy rice.

Various house designs and modifications have also been shown to minimise the number of mosquitoes that enter. This is not meant to be an exhaustive list of activities that can reduce mosquito numbers, but are examples to show that there are other activities that can be undertaken, without necessarily increasing the selection pressure for a less insecticide-susceptible mosquito population. Where feasible, they should always be included as part of vector control programmes.

Unintentional exposure

Mosquitoes can be exposed to insecticides in situations not directly related to their control. The agricultural and horticultural use of pesticides can unintentionally expose both adult and larval mosquitoes to selection pressure. This is particularly concerning when the insecticides used in agriculture are from the same mode of action groups as those used in vector control.

An integrated approach to vector control needs to engage with those involved with agriculture to minimise the number of mosquitoes associated with it. By limiting breeding sites, and minimising the potential for exposure to the agricultural use of insecticides, the overall number of mosquitoes can be reduced and selection pressure for insecticide resistance minimised.

The wider system

Malaria vector control doesn’t occur in isolation; it is part of a wider healthcare environment. In many malaria-endemic regions, there are other vector-borne diseases present. Dengue, chikungunya, yellow fever etc., are viral diseases vectored by Aedes species mosquitoes. Both malaria and these viral diseases, and their mosquito vectors, may be present in the same location. Activities aimed at controlling malaria vectors may impact the vectors of the viral diseases, and vice versa.

An integrated approach to vector control needs to take a holistic view and consider the use of all insecticide-based interventions, to maximise the impact on the mosquito populations, and to minimise the selection pressure for reduced susceptibility in all vector species present. This may become an increasingly important consideration with the spread of Anopheles stephensi in East Africa. Anopheles stephensi is a malaria vector that is well adapted to living in urban areas in similar habitats to the Aedes vectors of viral diseases.

Stakeholder engagement

Vector control programmes are undertaken to protect people from vector-borne disease. People are therefore at the heart of the ‘system’. A programme that fails to integrate the people – individuals, families, and communities – into its design and implementation, is missing a key component of the system.

While vector control programmes are coordinated at the national, regional, provincial or district levels, we must remember that interventions are deployed at the community level. Integration of efforts, for the optimal use of resources for vector control, needs to occur at all scales.

This means optimising not only the control of the mosquito vectors today, but also minimising the selection pressure for resistance development, ensuring they can be used successfully tomorrow.

A case study is presented as additional reading in the download section, looking at integrated efforts at the community and international scales.

Authors: Chadwick Sikaala and Mark Hoppé

© University of Basel
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The Resistant Mosquito: Staying Ahead of the Game in the Fight against Malaria

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