12th September, 2011
A recent paper published in The Lancet and entitled ‘Malaria morbidity and pyrethroid resistance after introduction of insecticide-treated bednets and artemisinin-based combination therapies: a longitudinal study’ has raised varied reactions across the world and doubt about the efficacy of long-term use of mosquito nets.
As an organisation working with African communities to improve their health, AMREF is greatly interested in the debate. Since 1983, AMREF has prioritised malaria control particularly at community level. It was one of the first organisations to be involved in evaluating the impact of Insecticide-Treated Nets (ITNs) at community level and is therefore keen on any issues related to the use of ITNs.
The study conducted by the Institut de Recherche pour le Developpement (IRD) showed a rebound effect of malaria incidence two years after the introduction of Long-Lasting Insecticidal Nets (LLINs) due to insecticide resistance. The findings suggest the following comments:
1. The authors have reinforced the importance of monitoring insecticide resistance within the framework of large use of LLINs and Indoor Residual Spray (IRS) in Africa. However the identification of pyrethoid resistance does not automatically mean lack of effectiveness. The concentrations of the tested product used in laboratories could be different from those used in the field.
2. Insecticide resistance is a threat to both malaria control and elimination. It must be addressed in a global manner, not viewed restrictively as malaria control. Indeed it is not unusual for the same population of mosquito to be exposed during their larvae stage to agricultural pesticides and during adult stage to domestic insecticides and other forms of vector control.
3. A combination of proven measures such
as accurate diagnosis, early treatment using ACT (Artemisinin Combination Therapy) and prevention with LLINs promotes efficacy for malaria control and prevention. As described by the authors malaria prevalence has dramatically decreased by 84% (from 16.3% in 2007 to 2.7% in 2010). The entomological inoculation rate has also fallen by 62% (from 232 in 2007 to 89, in 2010).
4. Decreasing immunity is a natural phenomenon which is expected in a population where effective control measures have significantly reduced malaria transmission. Such communities need close surveillance because any variation among factors such as rainfull may cause an increase in malaria cases. In addition, because the study was done in a short period of time and in one epidemiologic setting, further studies are needed to assess age shifts in malaria morbidity and mortality after scale-up of malaria interventions.
5. Malaria control requires the implementation of a package of proven interventions with community participation. Distributing LLINs without communications support and community commitment could not have ensured proper use of this protective tool. Given the fact that ITN coverage was 61% (less than 80%, which is the recommended rate to protect a community), there is no evidence that the study sample which did not have any contact with ITNs before 2008 – in contrast with the rest of the Senegalese population – and had no communication support, could use the nets correctly (hanging, washing, drying, tucking..). Furthermore this rebound effect was not noted in other parts of Senegal (North and South regions) with a long experience of ITN use.
6. Finally, the study was conducted in one village in rural Senegal involving 500 inhabitants, which cannot be representative of a country, with different epidemiological patterns, even less a continent.
With the excitement and reaction generated by this research, there is a risk of doubt and misinterpretation of results and discouragement of the international community in the fight against malaria and a reduction of LLIN use by communities. AMREF therefore calls for caution and reaffirms its commitment to promoting universal coverage of ITNs as an effective measure for malaria prevention. Moreover AMREF emphasises that malaria control must include a package of preventive and therapeutic measures according to local context and involving communities. Finally, both insecticides and anti-malarial drugs should be regularly monitored. Governments, civil society organisations and partners must support these activities and intensify efforts to prevent resistance.
