A cohort study of the effectiveness of insecticide-treated bed nets to prevent malaria in an area of moderate pyrethroid resistance, Malawi

Malaria Journal

Research

Paul Howell¹  John Gimnig¹  Ryan Wiegand¹  Laura Steinhardt¹  Kim A Lindblade¹  Jacklyn Wong¹  Monica Shah¹  Dyson Mwandama²  Themba Mzilahowa²  Don P Mathanga²  Andy Bauleni²  John Chiphwanya³  John Zoya³ 

[1] Division of Parasitic Diseases and Malaria, US Centers for Disease Control and Prevention, 1600 Clifton Rd. NE MS A-06, 30333, Atlanta, GA, USA;Malaria Alert Centre, Malawi College of Medicine, Blantyre, Malawi;National Malaria Control Programme, Ministry of Public Health, Lilongwe, Malawi;

关键词: Malaria;    Insecticide-treated bed nets;    Prevention;    Vector control;    Insecticide resistance;   

DOI  :  10.1186/s12936-015-0554-1

 received in 2014-10-18, accepted in 2015-01-07,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundInsecticide-treated bed nets (ITNs) are the cornerstone of malaria control in sub-Saharan Africa but their effectiveness may be compromised by the spread of pyrethroid resistance among malaria vectors. The objective of this investigation was to assess the effectiveness of ITNs to prevent malaria in an area of Malawi with moderate pyrethroid resistance.MethodsOne deltamethrin ITN was distributed in the study area for every two individuals in each household plus one extra ITN for households with an odd number of residents. A fixed cohort of 1,199 children aged six to 59 months was seen monthly for one year and at sick visits to measure malaria infection and use of ITNs. Insecticide resistance among malaria vectors was measured. The effect of ITN use on malaria incidence was assessed, adjusting for potential confounders using generalized estimating equations accounting for repeated measures.ResultsThere were 1,909 infections with Plasmodium falciparum over 905 person-years at risk (PYAR), resulting in an observed incidence of 2.1 infections per person-year (iPPY). ITNs were used during 97% of the PYAR. The main vector was Anopheles funestus: mortality in WHO tube assays after exposure to 0.05% deltamethrin was 38% (95% confidence interval (CI) 29–47), and resistance was due to elevated oxidase enzymes. After adjusting for potential confounders, the incidence of malaria infection among ITN users was 1.7 iPPY (95% CI 1.5-2.1) and among non-bed net users was 2.6 iPPY (95% CI 2.0-3.3). Use of ITNs reduced the incidence of malaria infection by 30% (rate ratio 0.7; 95% CI, 0.5-0.8) compared to no bed nets.ConclusionITNs significantly reduced the incidence of malaria infection in children in an area with moderate levels of pyrethroid resistance and considerable malaria transmission. This is the first study to show that ITNs provide protection in areas where pyrethroid-resistant An. funestus is the major malaria vector. Malaria control programmes should continue to distribute and promote ITNs in areas with low to moderate pyrethroid resistance; however, insecticide resistance may intensify further and it is not known whether ITNs will remain effective at higher levels of resistance. There is an urgent need to identify or develop new insecticides and technologies to limit the vulnerability of ITNs to insecticide resistance.

【 授权许可】

CC BY   
© Lindblade et al.; licensee BioMed Central. 2015