Insecticide-treated net coverage in Africa: mapping progress in 2000-07

Abstract

Background: Insecticide-treated bednets (ITNs) provide a means to improve child survival across Africa. Sales figures of these nets and survey coverage data presented nationally mask inequities in populations at biological and economic risk, and do not allow for precision in the estimation of unmet commodity needs. We gathered subnational ITN coverage sample survey data from 40 malaria-endemic countries in Africa between 2000 and 2007.

Methods: We computed the projected ITN coverage among children aged less than 5 years for age-adjusted population data that were stratified according to malaria transmission risks, proximate determinants of poverty, and methods of ITN delivery.

Findings: In 2000, only 1.7 million (1.8%) African children living in stable malaria-endemic conditions were protected by an ITN and the number increased to 20.3 million (18.5%) by 2007 leaving 89.6 million children unprotected. Of these, 30 million were living in some of the poorest areas of Africa: 54% were living in only seven countries and 25% in Nigeria alone. Overall, 33 (83%) countries were estimated to have ITN coverage of less than 40% in 2007. On average, we noted a greater increase in ITN coverage in areas where free distribution had operated between survey periods.

Interpretation: By mapping the distribution of populations in relation to malaria risk and intervention coverage, we provide a means to track the future requirements for scaling up essential disease-prevention strategies. The present coverage of ITN in Africa remains inadequate and a focused effort to improve distribution in selected areas would have a substantial effect on the continent's malaria burden.

Figure 1. Availability of insecticide-treated bednet (ITN) data for two study periods, delivery methods, poverty mapping, and risk of malaria

National boundaries are shown in black and first-level administrative boundaries are shown in white. (A) First-level administrative units used to define ITN use between 2000 and 2007. Countries shown in grey are those where no baseline or matched follow-up data were available (Botswana, Cape Verde, Comoros, Gabon, Liberia, and Reunion) or that were not at risk of Plasmodium falciparum malaria (Algeria, Egypt, Lesotho, Libya, Morocco, Tunisia, and seven provinces in South Africa). (B) Main delivery methods adopted by countries after 2000 and before follow-up national surveys as indicated in table 1. Light green is cost recovery through public sector or subsidised private or public sector; middle green is highly subsidised routine distribution through public sector; and dark green is free mass campaigns, either localised or nationally, or routine free distribution through public sector. (C) Poverty map showing the least poor quintile (light blue), the two moderately poor quintiles (middle blue), and the two poorest quintiles (dark blue), based on the mean brightness of night-time lights in the fi rst-level administration unit. (D) Map of malaria showing areas of no malaria risk (white) and those under unstable (light pink) and stable (dark pink) transmission.

Figure 2

Insecticide-treated bednet (ITN) coverage among children under the age of 5 years reported in (A) 1999-2003 (baseline) and (B) 2004-07 (follow-up), and (C) projected to July, 2007 (target period)

Figure 3. Insecticide-treated bednet (ITN) use among children under the age of 5 years in 2007 by the main country ITN delivery mechanism

The box indicates the IQR (25% and 75%); the thick line within the box represents the median; and the error bars represent the 2·5% and 97·5% centiles; and outliers are plotted as circles outside this range. ITN distribution was free (n=117), moderately or highly subsidised (n=117), and full cost recovery (n=50). The two malaria-endemic first-level administration units (ADMIN1) in South Africa (KwaZulu Natal and Mpumalanga) are not included. Median ITN coverage among children less than 5 years of age was higher in ADMIN1 without free distribution than in those with routine subsidised delivery (ANOVA p=0·05) or full cost recovery (p=0·02).