Reduction in confirmed malaria cases in Zambia: The effect of IRS in matched intervention and control districts

Zambia reinstated Indoor Residual Spraying (IRS) in selected districts in 2004 as an intervention against malaria resurgence, in addition to nationwide promotion and distribution of insecticide treated bednets, use of intermittent preventive treatment, and artemisinin-based combination therapy. To assess the role of IRS in reduction of malaria cases, a facility-based review was conducted in May 2009. Confirmed malaria cases as a proportion of all tested cases in one IRS intervention district were compared to those of an epidemiologically similar non-intervention district. Malaria cases confirmed by microscopy or HRP2-RDT were extracted from laboratory registers from three health facilities in each district from 2003 through 2008. The study showed reduction in confirmed cases as a proportion of all tested cases from 40.7% to 6.3% (84.5% reduction) in the IRS district of Kabwe and from 61.5% to 31.6% (51.4% reduction) in the non-IRS district of Mkushi. The observed reduction in proportion of confirmed cases in the non-IRS district may be attributed to other anti-malarial interventions which are present in all districts (ITNs, ACT, IPT). The data suggest that the addition of IRS to other interventions led to additional reductions in confirmed cases. The proportion of confirmed cases was lower among children under five than in those five and over, possibly due to increasing use of ITNs in this age group, as found in the Malaria Indicator Survey 2008. Recommendations: Consistent RDT use for confirming and reporting malaria cases; Attention to the correct diagnosis and treatment of other fever cases; Appropriate expansion of IRS.