Impact Of Indoor Residual Spraying (Irs) On Malaria Parasitaemia In Obuasi Metropolis

ABSTRACT Background: Malaria remains a significant source of morbidity and mortality in Ghana. The AngloGold Ashanti mining company in Obuasi in the Ashanti Region of Ghana concerned about the threats malaria poses to its operations instituted a comprehensive malaria control programme including Indoor Residual Spraying (IRS) in 2006. This district wide intervention against malaria needs to be evaluated and this report presents such analysis of the effect of the intervention on malaria parasitaemia in school children in the district. Methods: A cross-sectional survey was conducted prior to the IRS intervention in 2006 and two others after the intervention in 2007 and 2011 with the aim of evaluating the impact of IRS on parasitaemia levels in the Obuasi Municipality. In all, 2173 school aged children (from Kindergarten to JHS 3) were sampled. Data for this analysis was obtained from the pre (2006) and post IRS intervention surveys (2007 and 2011) that had been conducted by the Noguchi Memorial Institute for Medical Research Institution (NMMRI) over the five-year period. Simple proportions were used to determine the age-specific parasitaemia before and after IRS, the percentages of participants, who had fever or anaemia as well as parasitaemia for the different surveys that were conducted. The Logistic regression was also used to model the odds of parasitaemia before and after IRS to determine the association between the prevalence of parasitaemia and the number of spraying. Results: Of the 2173 school aged children sampled, 710, 828 and 635 children were recruited for the 2006, 2007 and 2011 surveys respectively. Parasite prevalence was v 45.5% (323 of 710) of children surveyed prior to the implementation of IRS (May, 2006), 22.66% (182 of 806) screened in the first survey after IRS (June, 2007) and 17.2% (109 of 633) screened in the second survey after IRS (November, 2011). Children in the 0 – 5 years age group had the least parasitaemia levels across all three survey periods. However, the highest parasitaemia levels were recorded among the 11 – 15 years age group before the spraying whereas >15 and 6 – 10 years age groups were found to have the highest parasitaemia levels during the first and second post intervention surveys respectively. After spraying two and eight times, there was a significant reduction in the malaria parasitaemia levels [0.50 (95% CI: 0.43 – 0.58) and 0.38 (95% CI: 0.31 – 0.46) respectively]. After adjusting for age and sex, a significant reduction again was observed; 0.48 (0.42 – 0.56) after two times of spraying and 0.40 (0.33 – 0.48) after eight more times of spraying. Conclusion: The IRS which was just one aspect of the comprehensive intervention programme instituted by the AngloGold Ashanti company, has proven to be effective in reducing the incidence of malaria in school aged children, since parasitaemia levels were significantly lower after its implementation (p