The Impact of 3 Years of Targeted Indoor Residual Spraying With Pirimiphos-Methyl on Malaria Parasite Prevalence in a High-Transmission Area of Northern Zambia

Abstract

Malaria transmission in northern Zambia has increased in the past decade, despite malaria control activities. Evidence-based intervention strategies are needed to effectively reduce malaria transmission. Zambia’s National Malaria Control Centre conducted targeted indoor residual spraying (IRS) in Nchelenge District, Luapula Province, from 2014 to 2016 using the organophosphate insecticide pirimiphos-methyl. An evaluation of the IRS campaign was conducted by the Southern Africa International Centers of Excellence for Malaria Research using actively detected malaria cases in bimonthly household surveys carried out from April 2012 to July 2017. Changes in malaria parasite prevalence after IRS were assessed by season using Poisson regression models with robust standard errors, controlling for clustering of participants in households and demographic, geographical, and climatological covariates. In targeted areas, parasite prevalence declined approximately 25% during the rainy season following IRS with pirimiphos-methyl but did not decline during the dry season or in the overall study area. Within targeted areas, parasite prevalence declined in unsprayed households, suggesting both direct and indirect effects of IRS. The moderate decrease in parasite prevalence within sprayed areas indicates that IRS with pirimiphos-methyl is an effective malaria control measure, but a more comprehensive package of interventions is needed to effectively reduce the malaria burden in this setting.

Malaria Outbreak Facilitated by Appearance of Vector-Breeding Sites after Heavy Rainfall and Inadequate Preventive Measures: Nwoya District, Northern Uganda, February–May 2018

“…A study in northern Uganda reported that whereas malaria prevalence reduction was realized within 3 months of IRS, the effects started to wane by the fourth month [44]. Another study in Zambia reported that IRS effectiveness using a specific insecticide was more effective during the rainy season than the dry season [45]. erefore, whereas IRS has positive gains in reducing malaria transmission, it should be applied consistently to sustain such gains.…”

Performance of IRS on malaria prevalence and incidence using pirimiphos-methyl in the context of pyrethroid resistance in Koulikoro region, Mali

“…3 Results of the stepwise multivariate logistic regression model between independent explanatory variables and parasitemia during October 2016 survey in the two study areas to the added value of the IRS in the IRS area. Indeed, it is of common knowledge that each of the LLINs [9,18,19] and IRS [20][21][22] significantly reduce malaria burden when deployed separately. Thus, their integration is expected and supported by many studies [7,21,[23][24][25] to make more reduction in malaria burden compared to their respective single impact.…”

“…Since the two areas are comparable in terms of malaria epidemiology and interventions, this difference can be attributed to the added value of the IRS in the IRS area. Indeed, it is of common knowledge that each of the LLINs [ 9 , 18 , 19 ] and IRS [ 20 – 22 ] significantly reduce malaria burden when deployed separately. Thus, their integration is expected and supported by many studies [ 7 , 21 , 23 – 25 ] to make more reduction in malaria burden compared to their respective single impact.…”

Performance of IRS on malaria prevalence and incidence using pirimiphos-methyl in the context of pyrethroids resistance in Koulikoro region, Mali

“…Since the two areas are comparable in terms of malaria epidemiology and interventions, this difference can be attributed to the added value of the IRS in the IRS area. Indeed, it is of common knowledge that each of the LLINs [9,18,19] and IRS [20][21][22] signi cantly reduce malaria burden when deployed separately. Thus, their integration is expected and supported by many studies [21,[23][24][25][26] to make more reduction in malaria burden compared to their respective single impact.…”