Netting the problem: how effective are insecticide-treated bednets against malaria?

Could widespread use of insecticide-treated bednets (ITNs) have a major and sustainable impact on the Africa rural malaria problem?  Is there a negative impact on older children who have not build up resistance to the disease because of protection when they were younger?  Would providing ITNs free of charge cost-effective? The London School of Hygiene and Tropical Medicine, together with the Tanzanian National Institute of Medical Research, studied how effective nets, treated with insecticide, were against malaria in children in Tanzanian villages, 3-4 years after the nets were introduced. 

ITNs were given to everybody living in the eight Tanzanian villages takingpart in the study.  During the course of the study the nets were retreated with insecticide (alphacypermethrin) each year.  The survey compared children aged between six months and 13 years whose nets were intact or torn and children with no nets in the villages where most people had nets. More than 90 per cent of the children responded to the surveys which took place in February 1999 and April 2000.  Four nearby villages at the same altitude of 200 metres which had not received the ITNs were chosen to act as controls.

 The study found that:

• the number of infective mosquito bites was greatly reduced in netted villages
• children from the eight villages, aged between six months and two years, were up to 75 per cent less likely to have fever with high malaria parasitaemia (the infection of the blood with parasites) and anaemia than children in other villages. Within the netted villages the children who did not themselves have nets were nearly as well protected as those with their own nets as a result of the community-wide effect on the mosquito population.
• the benefits for older children were less clear.  However there was no evidence to suggest that older children were more likely to suffer the effects of malaria because they had not built up resistance to the disease when they were younger.

Thus the benefits to the community of using ITNs continued over the four years of the study. The report concludes that:

• it is important to provide the ITNs free of charge since relying on the marketing does not provide sufficient coverage in rural areas to achieve the full potential of treated nets to reduce the mosquito population in the community
• urban areas have little malaria and a thriving market in ITNs, but subsistence farmers in lowland areas have little spare cash to spend
• providing ITNs every four years and re-treating them annually costs about US$ 1 per person per year. In light of this, the few hundred million dollars a year necessary to protect the whole of rural Africa would be money well-spent.

 

Source(s):
‘Effect of community-wide use of insecticide-treated nets for 3-4 years on malarial morbidity in Tanzania’, Tropical Medicine and International Health 7(12): 1003-1008, by C.A. Maxwell et al, 2002 
HINARI subscribers can access the full-text article here. Full document.

Funded by: British Medical Research Council

id21 Research Highlight: 23 April 2003

Further Information:
 Chris Curtis
London School of Hygiene and Tropical Medicine
Keppel Street
London 
WC1E 7HT
UK

Tel: +44 (0)207 927 2339
Fax: +44 (0)207 636 8739
Contact the contributor: chris.curtis@lshtm.ac.uk

London School of Hygiene and Tropical Medicine, UK

Tanzanian National Institute for Medical Research

Other related links:
'A small price to pay: preventing malaria in rural Afghanistan'

'Net cost - affording bednets in rural highland Kenya'

'Casting the net – free bednets for pregnant Kenyan women'

'Control panel - tools to prevent malaria epidemics in highland Africa'

See id21's collection of links relevant to infectious diseases.