Malaria Control

Overview

Malaria remains a serious global health problem with half of the world’s population at risk. The greatest burden is in sub-Saharan Africa where over 800,000 lives are lost each year. In the past five years, the level of resources and the degree of national and international commitment to malaria control has been scaled up dramatically. The impact of this is now being felt in many malaria endemic regions. For the first time in a generation, malaria is on the decline in some parts of Africa. This is principally due to the scale up of two indoor vector control interventions, long lasting insecticide impregnated bednets (LLINs) and indoor residual spraying with insecticides (IRS), coupled with effective antimalarial drug treatment.

Indoor insecticide based interventions such as LLINs and IRS are particularly effective in Africa because they intentionally target the behavioural characteristics of the two major mosquito vectors, Anopheles gambiae s.s and Anopheles funestus. LLINs work because these vectors generally feed at night when people are asleep. The nets protect people from bites and kill vectors. IRS works because vectors rest inside houses after biting (blood feeding). If walls are sprayed with insecticides, vectors are killed and cannot transmit malaria.

With political and financial momentum driving the scale-up of LLINs and, to a lesser extent IRS, the role that other methods of vector control can play in contributing to the reduction in the malaria burden is sometimes overlooked. The benefits of integrating vector control strategies into national and community control programmes is not always fully realised. Targeting the larval (immature) stages of the mosquito in their aquatic habitats, either by environmental modifications or the application of larvicides, can be very effective, especially where routine treatment can be targeted at key breeding sites. However this intervention has not been implemented at large scale in Africa since the 1960’s.

Numerous vector control measures have been tested in the laboratory or in field situations but have not yet been translated into effective interventions. Some of these, such as genetic modification of vector species to make them unable to transmit the malaria parasite, are still under development and most agree that they are many years away from large-scale field trials. Further along the development pathway are tools such as entomopathogenic (insect killing) fungi that have shown potential in pilot studies and now await further demonstration of epidemiological effectiveness and sustainability. Other vector control measures, such as house screening, have performed well in large-scale trials but have not yet been implemented at programmatic level.

Limitations of current vector control strategies

Weak health systems cannot deliver proven interventions such as LLINs and IRS at the required scale and quality. This hinders vector control in Africa. However, even if universal coverage with current interventions was achieved, it is clear that this will not meet the needs of the coming decades for sustainable malaria control in Africa. Some of the major challenges include:

Summary

The methods used for malaria vector control in Africa are effective but not sufficient and face several emerging threats to their efficacy. They must be supplemented by new tools that can be integrated with existing interventions, in a range of different malaria transmission scenarios to target all vector species. They must be safe-guarded by investing in evaluating alternative insecticides or delivery mechanisms that will minimise the impact of insecticide resistance.

The AvecNet Project has been designed to meet these challenges. Further information on how this will be achieved can be found here.