Impact of Indoor Residual Spraying with Lambda-Cyhalothrin on Malaria Parasitemia and Anemia Prevalence among Children Less than Five Years of Age in an Area of Intense, Year-Round Transmission in Malawi

The American Journal of Tropical Medicine and Hygiene, Jun 2012

Jacek Skarbinski, Dyson Mwandama, Adam Wolkon, Madalitso Luka, James Jafali, Alison Smith, Themba Mzilahowa, John Gimnig, Carl Campbell, John Chiphwanya, et al.

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Impact of Indoor Residual Spraying with Lambda-Cyhalothrin on Malaria Parasitemia and Anemia Prevalence among Children Less than Five Years of Age in an Area of Intense, Year-Round Transmission in Malawi

0 ters for Disease Control and Prevention , 4770 Buford Highway NE, Mailstop F22, Atlanta, GA 30341 1 Dyson Mwandama , Adam Wolkon, Madalitso Luka, James Jafali, Alison Smith, Themba Mzilahowa, John Gimnig, Carl Campbell, John Chiphwanya, Doreen Ali, and Don P. Mathanga Malaria Branch, and Entomology Branch , Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention , Atlanta , Georgia; Malaria Alert Centre, and Department of Community Health, College of Medicine , Blantyre , Malawi; Center for Tropical and Global Emerging Diseases, University of Georgia , Athens , Georgia; National Malaria Control Programme, Ministry of Health , Lilongwe , Malawi Little is known about the impact of indoor residual spraying (IRS) in areas with intense malaria transmission such as sub-Saharan Africa. In Malawi, IRS with lambda-cyhalothrin has been applied annually in an area of intense year-long transmission since 2007. We evaluated the impact of IRS on parasitemia and anemia prevalence in children less than five years of age by using a cross-sectional household survey conducted in 2009, six months after the second IRS spray round. We measured malaria parasitemia and anemia (hemoglobin level < 11 g/dL) in 899 children less than five years of age and used binomial regression to assess the impact of IRS by comparing children living in a household sprayed with IRS (direct IRS) with those in a household not sprayed with IRS, but in an IRS area (indirect IRS) and those living in a household not sprayed with IRS and not in an IRS area (no IRS). In the IRS area, 77% of households reported receiving IRS. Adjusting for bed net use, house construction, and socioeconomic status, we found that receiving direct IRS and indirect IRS were significantly associated with a 33% (95% confidence interval [CI] = 1-54%) and 46% (95% CI = 20-64%) reduction in parasitemia and a 21% (95% CI = 4-34%) and 30% (95% CI = 12-45%) reduction in anemia prevalence, respectively. - Vector control interventions such as insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are key malaria control tools.1,2 Both of these strategies depend on the action of insecticide either sprayed onto the wall or applied to the netting material to kill adult female anopheline mosquitoes either before or after a blood meal and reduce both the size and longevity of the adult mosquito population. In addition, some insecticides, including the synthetic pyrethroids, also repel mosquitoes from households, leading to reduced humanmosquito contact and increased mortality of adult mosquitos.3 Lastly, bed nets provide a physical barrier to humanmosquito contact. Both ITNs and IRS are most effective for endophagic and endophilic mosquito vectors, where they provide a community-wide effect; thus persons who do not receive personal protection can still benefit from these interventions in their communities.35 Insecticide-treated nets have proven effective in a large number of field trials and have been shown to reduce mortality in children 159 months of age, asexual malaria parasitemia, and anemia prevalence, as well as uncomplicated malaria and severe malaria incidence.6 In recent years, because of their proven efficacy and relative ease of implementation, ITNs have become the predominant vector control strategy in many malaria-endemic areas of the world.2 Evidence of IRS efficacy in reducing or interrupting malaria transmission has been available since the 1940s, and many historical examples of successful IRS programs exist from the Global Malaria Eradication Program era in the 1950s to 1970s.7 However, IRS was not a major component of malaria control as part of the Global Malaria Eradication Program or afterwards in areas with intense, year-round transmission such as most of sub-Saharan Africa. Much of our early data on IRS efficacy in areas with intense, year-long malaria transmission comes from relatively small scale demonstration projects and cluster randomized trials.812 More recently, IRS use has increased in sub-Saharan Africa and has had demonstrated impact in a number of different transmission settings.1321 In 2006, the World Health Organization has revised its recommendation for the use of IRS and endorsed IRS use in all malaria transmission zones, including much of sub-Saharan Africa.1 Although some historical examples of IRS use in high transmission settings exist,9,10,22 there is a paucity of recent data on IRS use in areas of intense, year-long malaria transmission. Although IRS and ITNs have been shown to be effective at reducing malaria transmission,6,11 there are unanswered questions about their relative efficacy8 and cost effectiveness,2325 as well as the additional protection afforded by the combined use of IRS and ITNs.11,26 There are few head-to-head comparisons of ITN and IRS efficacy, and the data thus far are mixed. A review of six previously conducted studies across sub-Saharan Africa and South Asia concluded that I (...truncated)


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Jacek Skarbinski, Dyson Mwandama, Adam Wolkon, Madalitso Luka, James Jafali, Alison Smith, Themba Mzilahowa, John Gimnig, Carl Campbell, John Chiphwanya, Doreen Ali, Don P. Mathanga. Impact of Indoor Residual Spraying with Lambda-Cyhalothrin on Malaria Parasitemia and Anemia Prevalence among Children Less than Five Years of Age in an Area of Intense, Year-Round Transmission in Malawi, The American Journal of Tropical Medicine and Hygiene, 2012, pp. 997-1004, 86/6, DOI: 10.4269/ajtmh.2012.11-0621