Impact of DDT re-introduction on malaria transmission in KwaZulu-Natal.

OBJECTIVES: To determine whether the re-introduction of DDT in KwaZulu-Natal had any effects on malaria transmission in the province. DESIGN, SETTING AND SUBJECTS: The 2000 malaria epidemic in KwaZulu-Natal has been attributed to pyrethroid-resistant anopheles mosquitoes in the area. Previous studies have shown that these mosquitoes are still susceptible to DDT. To determine whether DDT re-introduction had any impact on malaria transmission in KwaZulu-Natal, the following variables (pre- and post-epidemic) were investigated: (i) the number of reported cases; and (ii) the distribution of Anopheles funestus in relation to the insecticides sprayed. OUTCOME MEASURES: The notified malaria cases and the distribution of A. funestus were measured to determine the effects of DDT re-introduction on malaria transmission. RESULTS AND CONCLUSION: After DDT re-introduction, the number of malaria cases decreased to levels lower than those recorded before the epidemic. A. funestus appears to have been eradicated from the province. The combination of an effective insecticide and effective antimalarial drugs in KwaZulu-Natal has resulted in a 91% decline in the malaria incidence rate. Unfortunately the continued exclusive use of DDT within the malarious areas of the province is threatened by the emergence of insecticide resistance.

Comparison of the cost and cost-effectiveness of insecticide-treated bednets and residual house-spraying in KwaZulu-Natal, South Africa.

Residual house-spraying (RHS) has been the mainstay of South African malaria prevention for more than 50 years, but it has been argued that insecticide-treated bednets (ITBN) could be a more effective and appropriate method of control. To provide a rational basis for choosing between the interventions, a trial was conducted during 1998 and 1999 in northern KwaZulu-Natal to collect comparable data on the effectiveness, acceptability and cost of the two interventions. The current practice of house-spraying once a year was compared with ITBN, distributed free to households and retreated annually at several specific centres. The base case results show ITBN to be significantly more effective in preventing malaria cases than RHS (overall adjusted rate ratio of 0.69), and also more costly, with an incremental economic cost per person of ITBN compared with RHS of R8.68 (US$1.42) per year, giving a gross incremental cost per case averted of R111 ($18) (1999 prices). Estimating the number of deaths averted, based on the average case fatality rate, gave a gross incremental cost per death averted of R11 718 ($1915). The additional cases averted were estimated to lead to drug cost savings of around R1 ($0.16) per capita per year, giving a net cost per case averted of R98 ($16), and net cost per death averted of R10 377 ($1696). Although the finding that the economic costs of ITBN were higher than those for RHS was relatively robust to parameter variations, the extent of the cost margin was sensitive to changes in the price and useful life of the net, and the price of the insecticide. Moreover, a switch to ITBN could lead to net financial savings if the price per net fell below $3.57 (R21.85), or if a change in policy allowed a significant reduction in the number of permanent full-time malaria control staff. In view of the greater effectiveness of ITBN, policy makers may view ITBN as a cost-effective use of resources, even if the economic costs are higher. If ITBN are implemented, close monitoring will be required of use, retreatment and useful life of nets, and resistance to insecticides, to assess any change over time in relative cost-effectiveness, and any threat to the role of the programme as a barrier to the spread of malaria transmission to other areas.

Malaria control--two years' use of insecticide-treated bednets compared with insecticide house spraying in KwaZulu-Natal.

OBJECTIVES: The objective of this study was to produce data indicating whether insecticide-treated bednets should replace insecticide house spraying as a malaria control method in South Africa. We report 2 years of preliminary data on malaria incidence comparing areas receiving insecticide-treated bednets and those subjected to house spraying in northern KwaZulu-Natal. DESIGN, SETTING AND SUBJECTS: In order to measure significant reductions in malaria incidence between the two interventions, a geographical information system (GIS) was used to identify and create seven pairs of geographical blocks (areas) in the malaria high-risk areas of Ndumu and Makanis in Ingwavuma magisterial district, KwaZulu-Natal. Individual blocks were then randomly allocated to either insecticide-treated bednets or house spraying with deltamethrin. Malaria cases were either routinely recorded by surveillance agents at home or were reported to the nearest health facility. RESULTS AND CONCLUSIONS: The results show that 2 years' use of insecticide-treated bednets by communities in Ndumu and Makanis, KwaZulu-Natal, significantly reduced the malaria incidence both in 1997 (rate ratio (RR) = 0.879, 95% confidence interval (CI) 0.80-0.95, P = 0.04) and in 1998 (RR = 0.667, CI 0.61-0.72, P = 0.0001). Using a t-test, these significant reductions were further confirmed by an assessment of the rate of change between 1996 and 1998, showing a 16% reduction in malaria incidence in blocks using treated bednets and an increase of 45% in sprayed areas (t = 2.534, P = 0.026 (12 df)). In order to decide whether bednets should replace house spraying in South Africa, we need more data on the efficacy of treated bednets, their long-term acceptability and the cost of the two interventions.