Rose Crane and Stephanie Wilmore make argue their case well.  Make sure you also read their elective report of their time in Gai

At 2am on August 17^th in Gai, Eastern Kenya, we were awake, pacing the floor. The source of our worries: 3700 Long-Lasting Insecticide-treated Nets (LLINs) suspended in transit between here and Nairobi.  Three hours previously, over a crackling line, the truck driver had announced he was going to park for the night and sleep.  Preoccupied with the fate of our precious cargo and 50km from the nearest internet cafe, we were unaware that, just hours previously, the WHO had released a ground-breaking Position Statement (1) relevant to the very task we had set out to accomplish.  Three weeks later, by the time we had safely delivered our nets to 1318 households in 23 villages and returned to the UK, this Statement had sparked news interest as far and wide as the Hindu Times (2) to the magazine ‘Africa Today’. (3)

The WHO Statement of August 16^th anticipated the publication of a longitudinal study of the impact of the recent scaling-up of bednet coverage in Kenya. (4) Its timing - ahead of the paper’s peer review and publication - sparked controversy.(5-6)  In contrast to the WHO, now emphatically endorsing free distribution of nets to all community members (not just children and pregnant women), a Lancet Comment published alongside the Kenya study favoured programme diversity: a combination of free mass distributions, social marketing, and the retail sector. (7)

These findings of Fegan and colleagues renewed debate on how best to deliver nets.  The study aimed to calculate the effect of ITN use on child survival in four rural districts of Kenya. Social marketing and free distribution had been employed to achieve high ITN coverage in some areas.  A 44% reduction in child mortality was found, albeit with a wide 95% confidence interval of 3 to 96% (p=0.04).  These findings, thanks to the WHO Position Statement, received extensive press coverage and may impact heavily on future bednet distribution strategies.  

Net use in Kenyan children under five rose dramatically from 7% in 2004, to 23.5% in 2005, to 67% in 2006.(8) The initial progress was achieved through social marketing: the selling goods for the benefit of society.  Greater subsidies for children and pregnant women were introduced by the NGO Population Services International (PSI) in 2004. (9) [4] Healthcare facilities were invited to buy each net for 30 Kenyan Shillings (£0.21) and sell it on to a pregnant mother or child attending an appointment for immunisation or ante-natal care at a small mark-up for 50 Shillings.

A nominal fee is said to increase perception of quality, but this limits the subsidised sale to those who can afford to pay. In July this year Teklehaimanot called for all malaria-endemic countries to abandon social marketing; that ITNs should be viewed as public goods and distributed free to all. (10)

Our experience in Gai echoed these conclusions: even these heavy subsidies are often inadequate. 50 Shillings was impractical for many families. The nearby clinic at Katakani did not have a second fridge, and therefore could not store vaccines. No vaccine appointments, no PSI nets, and the children of Katakani missed out. We estimated coverage in the Gai area at 17% in August 2006, and our pilot distribution of 300 nets at that time revealed high demand for more. We were surprised that even most of the clinic staff - comparatively well-off and alerted to the benefits of ITN use - did not own one. Awareness was high: most wanted a net but lacked funds for one.

A national malaria strategy was launched by the Ministry of Health of Kenya in 2001.   Increasing ITN coverage was a main feature.  Five years later the Global Fund, the world’s largest financier of bednets, donated US$17 million towards 3.4 million LLINs for Kenyan children. (10) The government distributed these for free over two weeks through vaccination campaigns, schools and door-to-door.   In areas where social marketing had hitherto achieved only 3% coverage amongst the poorest children, this increased to two thirds of all children irrespective of wealth. (8) It is at these kinds of densities of net use that a second beneficial effect starts to be felt: the ‘mass effect’.

The action of treated nets extends beyond personal protection.   When many are in use the chance of a mosquito living long enough for the Plasmodium sporozoite to mature (12 days) is reduced.  The proportion of infective mosquitoes decreases, and those who do not sleep under a net are protected too. This is the ‘community-wide’ or ‘mass effect’ and is comparable to the concept of herd immunity in public health vaccination campaigns. 

Fegan and colleagues classified each of their 3,500 children into four quartiles depending upon the percentage bednet coverage in each child’s community.  The top end of the fourth quartile was just 62% coverage: none of their study sites had coverage close to 100%.  This figure is less than the level of coverage cited by Killeen et al as a minimum to bring about a significant mass effect. (11) perhaps this is what Fegan and colleagues allude to when they acknowledge that the impact of ITNs may be greater in districts of Kenya that have achieved higher coverage.  This may also be why no evidence for a mass effect was found prior to their standardisation for level of community coverage: the level of coverage in these districts is not high enough for the full mass effect to take place.

If true, this finding can only strengthen the case for free mass distribution: this is the only way to achieve sustained high density net coverage, to maximise the impact of a single mosquito net on malaria morbidity and mortality not only amongst the person who is lucky enough to be sleeping under it but also amongst his neighbour who is nearly as lucky to be sleeping in a village with high net coverage and a low mosquito population.

The people of Gai wanted nets but could not afford them. We hope that, as the evidence grows for the efficacy of free mass distribution, more malaria-endemic villages in Africa can benefit from this necessity.

Stephanie MS Wilmore and Rose J Crane
Royal Free and University College Medical School,
London WC1E 6BT
s.wilmore@ucl.ac.uk, and  r.crane@ucl.ac.uk

(1) World Health Organisation News Release. WHO releases new guidance on insecticide-treated mosquito nets. 16/08/2007.

(2) Xan Rice 20/08/07 The Hindu (ePaper) Nets halve child deaths from malaria. http://www.thehindu.com/2007/08/20/stories/2007082059731800.htm (Accessed: 30/09/2007)

(3) Akpata-Ohohe B. Kenya: new course of action on ITN, Africa Today. , 31/08/07 <http://africatoday.eh7.co.uk/cgi-bin/public.cgi?sub=news&action=one&cat=65&id=1153>

(4) Fegan GW, Noor AM, Akhwale WS, Cousens S, Snow RW, Effect of expanded insecticide-treated bednet coverage on child survival in rural Kenya: a longitudinal study. Lancet 2007; 370: 1035-39.

(5) Science at WHO and UNICEF: the corrosion of trust. Lancet Editorial 2007; 370: 1007.

(6) Kochi A. Science at WHO. Lancet Editorial published online October 1 2007 DOI: 10.1016/s0140-6736(07)61518-9.

(7) Lengeler C. Programme diversity is the key to success of insecticide-treated bednets. Lancet 2007; 370: 1009-10.

(8) Noor AM, Amin AA, Akhwale WS, Snow RW. Increasing access and decreasing inequity to insecticide-treated net use among rural Kenyan children. PLoS Med 2007; 4: e255.

(9) Population Service International Malaria Control Kenya Brief. Mosquito net coverage of vulnerable groups reaches 50% in Kenya. April 2006. <http://www.psi.org/malaria/pubs/Kenya-ITN-program.pdf>

(10)Teklehaimanot A, Sachs JD, Curtis C. Malaria control needs mass distribution of insecticidal bednets. Lancet 2007; 369: 2143-36.

(11) Killeen GF, Smith TA, Ferguson HM, Mshinda H, Abdulla S, Lengeler C, Kachur SP. Preventing childhood malaria in Africa by protecting adults from mosquitoes with insecticide-treated nets. PLoS Med 2007; 4(7): e229.

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