The Impact of Three Years of Targeted Indoor Residual Spraying with Pirimiphos-Methyl on Household Vector Abundance in a High Malaria Transmission Area of Northern Zambia

View More View Less
  • 1 Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland;
  • 2 W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland;
  • 3 Macha Research Trust, Choma, Zambia;
  • 4 The Tropical Diseases Research Centre, Ndola, Zambia;
  • 5 Department of Public Health, Michael Chilufya Sata School of Medicine, The Copperbelt University, Kitwe, Zambia

The global malaria burden has decreased substantially, but gains have been uneven both within and between countries. In Zambia, the malaria burden remains high in northern and eastern regions of the country. To effectively reduce malaria transmission in these areas, evidence-based intervention strategies are needed. Zambia’s National Malaria Control Centre conducted targeted indoor residual spraying (IRS) in 40 high-burden districts from 2014 to 2016 using the novel organophosphate insecticide pirimiphos-methyl. The Southern and Central Africa International Centers of Excellence for Malaria Research conducted an evaluation of the impact of the IRS campaign on household vector abundance in Nchelenge district, Luapula Province. From April 2012 to July 2017, field teams conducted indoor overnight vector collections from 25 to 30 households per month using Centers for Disease Control light traps. Changes in indoor anopheline counts before versus after IRS were assessed by species using negative binomial regression models with robust standard errors, controlling for geographic and climatological covariates. Counts of Anopheles funestus declined by approximately 50% in the study area and within areas targeted for IRS, and counts of Anopheles gambiae declined by approximately 40%. Within targeted areas, An. funestus counts declined more in sprayed households than in unsprayed households; however, this relationship was not observed for An. gambiae. The moderate decrease in indoor vector abundance indicates that IRS with pirimiphos-methyl is an effective vector control measure, but a more comprehensive package of interventions is needed with sufficient coverage to effectively reduce the malaria burden in this setting.

Author Notes

Address correspondence to Marisa A. Hast, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St. Baltimore, MD 21205. E-mail: marisahast@gmail.com

Financial support: This work was supported by funds from the National Institutes of Health awarded Southern and Central Africa International Centers of Excellence in Malaria Research (ICEMR) 3U19AI089680, the Bloomberg Philanthropies, and the Johns Hopkins Malaria Research Institute (JHMRI).

Authors’ addresses: Marisa A. Hast, Timothy Shields, William J. Moss, and Douglas E. Norris, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, E-mails: mhast2@jhu.edu, tshields@jhu.edu, wmoss1@jhu.edu, and douglas.norris@jhu.edu. Jennifer C. Stevenson, Macha Research Trust, Choma, Zambia, E-mail: jennyc.stevenson@macharesearch.org. Mbanga Muleba, Mike Chaponda, and Jean-Bertin Kabuya, Tropical Diseases Research Centre, Ndola, Zambia, E-mails: mulebam@tdrc.org.zm, chapondam@tdrc.org.zm, and kabuyaj@tdrc.org.zam. Modest Mulenga, The Copperbelt University, Kitwe, Zambia, E-mail: m.mulenga@hotmail.com.

Save