title: Reduction in Malaria Incidence following Indoor Residual Spraying with Actellic 300 CS in a Setting with Pyrethroid Resistance: Mutasa District, Zimbabwe.
abstract: BACKGROUND
  More than half of malaria cases in Zimbabwe are concentrated in Manicaland Province, where seasonal malaria epidemics occur despite intensified control strategies. Recently, high levels of pyrethroid and carbamate resistance were detected in Anopheles funestus, the major malaria vector in eastern Zimbabwe. In response, a single round of indoor residual spraying (IRS) using pirimiphos-methyl (an organophosphate) was implemented in four high burden districts of Manicaland Province from November 1, 2014 to December 19, 2014. The objective of this study was to evaluate the effect of this programmatic switch in insecticides on malaria morbidity reported from health care facilities in Mutasa District, one of the worst affected districts in Manicaland Province.
  
  
  METHODS
  The number of weekly malaria cases for each health facility 24 months prior to the 2014 IRS campaign and in the subsequent high transmission season were obtained from passive case surveillance. Environmental variables were extracted from remote-sensing data sources and linked to each health care facility. Negative binomial regression was used to model the weekly number of malaria cases, adjusted for seasonality and environmental variables.
  
  
  RESULTS
  From December 2012 to May 2015, 124,206 malaria cases were reported from 42 health care facilities in Mutasa District. Based on a higher burden of malaria, 20 out of 31 municipal wards were sprayed in the district. Overall, 87.3% of target structures were sprayed and 92.1% of the target population protected. During the 6 months after the 2014 IRS campaign, a period when transmission would have otherwise peaked, the incidence of malaria was 38% lower than the preceding 24 months at health facilities in the sprayed wards.
  
  
  CONCLUSIONS
  Pirimiphos-methyl had a measurable impact on malaria incidence and is an effective insecticide for the control of An. funestus in eastern Zimbabwe.
authors.affiliation: Department of International Health, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Mufaro
authors.initials: M
authors.lastname: Kanyangarara
authors.affiliation: Biomedical Research Training Institute, Harare, Zimbabwe.
authors.forename: Edmore
authors.initials: E
authors.lastname: Mamini
authors.affiliation: Biomedical Research Training Institute, Harare, Zimbabwe.
authors.forename: Sungano
authors.initials: S
authors.lastname: Mharakurwa
authors.affiliation: Biomedical Research Training Institute, Harare, Zimbabwe.
authors.forename: Shungu
authors.initials: S
authors.lastname: Munyati
authors.affiliation: Biomedical Research Training Institute, Harare, Zimbabwe.|Department of Medical Laboratory Sciences, University of Zimbabwe College of Health Sciences, Harare, Zimbabwe.
authors.forename: Lovemore
authors.initials: L
authors.lastname: Gwanzura
authors.affiliation: Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Tamaki
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Timothy
authors.initials: T
authors.lastname: Shields
authors.affiliation: Department of International Health, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Luke C
authors.initials: LC
authors.lastname: Mullany
authors.affiliation: National Institute of Health Research, Harare, Zimbabwe.
authors.forename: Susan
authors.initials: S
authors.lastname: Mutambu
authors.affiliation: Biomedical Research Training Institute, Harare, Zimbabwe.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Mason
authors.affiliation: Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Frank C
authors.initials: FC
authors.lastname: Curriero
authors.affiliation: Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: William J
authors.initials: WJ
authors.lastname: Moss
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects; D006801:Humans; D015994:Incidence; D007305:Insecticide Resistance / Q000187:drug effects*; D007306:Insecticides / Q000494:pharmacology*; D008288:Malaria / Q000453:epidemiology* / Q000517:prevention & control; D009032:Mosquito Control; D009946:Organothiophosphorus Compounds / Q000494:pharmacology*; D015030:Zimbabwe / Q000453:epidemiology
chemical_list: D007306:Insecticides; D009946:Organothiophosphorus Compounds; C014153:pirimiphos methyl