A malaria control trial using insecticide-treated bed nets and targeted chemoprophylaxis in a rural area of The Gambia, West Africa

Abstract

A large-scale malaria intervention programme using insecticide-treated bed nets and chemoprophylaxis administered to children was introduced into a rural area of The Gambia. The operation was carried out using the existing primary health care (PHC) service in the region. Training of the village health workers, sensitization of the communities, and implementation of net impregnation and the drug delivery programme are described. This delivery system resulted in over 90% of nets being treated with insecticide and 80% of children receiving over 90% of their tablets during the rainy season. There was considerable variation in the distribution of permethrin on a bed net and between individual nets, which is likely to facilitate the spread of insecticide resistance in the local mosquito populations. Bed nets made from heavier fabrics tended to absorb more insecticide than those made from lighter materials. Four months after dipping, 89% of the insecticide had been lost from treated nets. This was probably due mainly to women washing their nets, an activity carried out on average once every 2 months during the rainy season. The high number of insecticide-treated bed nets in the study area demonstrated that a malaria control programme operated through a PHC system can be implemented successfully.

Rebound mortality and the cost‐effectiveness of malaria control: potential impact of increased mortality in late childhood following the introduction of insecticide treated nets

“…The maximum reported estimates of malaria specific mortality rates in African children under 5 years range from 11 to 19 per 1000 children (Snow & Marsh 1995;Lengeler et al 1997). Excluding children less than one year of age, the highest reported malaria mortality rates in the 1-4 years age class are around 11 per 1000 children per year (Greenwood et al 1987;Alonso et al 1993b;Nájera & Hempel 1996). The data on malaria mortality in children 5-9 years of age are more scarce.…”

“…A linear relationship was assumed between compliance and effectiveness, such that zero compliance results in zero effectiveness, and 65% compliance results in the reductions in mortality and morbidity found in the meta-analysis. The retreatment rates under programme conditions are likely to be much lower than under trial conditions, and were given a range between 20% and 80% (Chavasse et al 1999), while between 50% and 97% of children were assumed to correctly use the net (Alonso et al 1993a;D'Alessandro et al 1995a;Binka et al 1996;Nevill et al 1996;Habluetzel et al 1997). These two estimates were multiplied together to calculate actual compliance.…”

“…The size of the reduction in all-cause mortality in children under 5 years using ITNs found in the WHO/TDR trials was greater than would have been expected from data on malaria specific mortality alone, possibly due to a reduction in indirect malaria mortality. Moreover, reductions in deaths attributed to acute respiratory infections, acute gastroenteritis and malnutrition were also found in the trials (Alonso et al 1993b;Binka et al 1996). The extent of indirect malaria mortality is very difficult to measure and is not well understood, but it is thought to be less likely to occur among older children.…”

“…The efficacy of insecticide treated nets (ITNs) for the control of malaria in children less than five years of age in subSaharan Africa (SSA) has recently been demonstrated by several large-scale trials (Alonso et al 1993b;D'Alessandro et al 1995a;Binka et al 1996;Nevill et al 1996;Habluetzel et al 1997). A reduction in all-cause mortality among children less than 5 years of age ranging from 14 to 63% has been recorded across a range of malaria transmission intensities,…”

A simple field test for detecting pyrethroids on impregnated nets

“…However, in routine Table 2 Sensitivity of a modified Beilstein test after impregnation with permethrin 50 EC at a dose of 0.5 ga.i./m 2 , using different materials and sizes of netting material and for 3 different extraction times (n ϭ 10 for each situation, N ϭ 300) Percentage of positive bed net samples (95% Confidence Intervals) unwashed (U), washed with water (W) and washed with soap (WS) using 2 ml to 10ml acetone (combined data). (Alonso et al 1993;Lines 1996). With different netting materials and different sizes of bednets available, it is difficult to define the exact amount of water that will be absorbed.…”