Effect of vector control on malaria incidence in Tororo: a case for focusing surveillance to sub-county levels

Tororo is one of the highest malaria transmission districts in Uganda. Universal distribution of LLINs in 2013 and IRS in 2014 were introduced to control malaria transmission in the district, but their effect on the disease incidence is not known and the district has no documented malaria epidemic detection thresholds. The objectives of the analysis were to describe malaria trend, assess the effect of vector control interventions and to establish a district malaria surveillance thresholds for Tororo district. A descriptive analysis of aggregate surveillance data from 2013 to 2015 from DHIS2. Data were analyzed in Microsoft excel to make weekly, monthly and annual trend graphs of malaria incidence. The number of malaria cases reported included both the laboratory and clinically diagnosed. The percentage of malaria cases in Out Patient Department per year, malaria laboratory test positivity rates and incidence by sub-county were determined. We set the district malaria surveillance threshold using the five week moving mean. Universal distribution of LLINs in 2013 reduced malaria incidence in 2014 by 10%, but did not change the high endemic transmission. A combination of IRS and LLINs caused a greater reduction in malaria incidence from 59/1000 in April 2014 to 28/1000 in April 2015 and reduced the high transmission. Malaria incidence reduction by sub-county was not uniform and needs specific thresholds. Malaria incidence in Tororo has been reducing since introduction of vector control interventions. Malaria incidence varied by sub-county. Heterogeneity of malaria transmission needs sub-county specific surveillance thresholds for early detection of epidemics.