Spatial Profiling Of Malaria Epidemiology In A Highland Area Of Low Endemicity: Transmission, Diagnosis And Malarial Anaemia In Nandi County-Kenya

ABSTRACT

Malaria remains prevalent in many parts of Kenya but areas in the highlands of Nandi North sub-county have reported declining incidences of malaria infection and disease burden, and between April 2007 and March 2008 a possible interruption of transmission was reported. Given the low transmission intensity in the current study sites, it is not clear if fever and/or a combination of other symptoms are accurate predictors of malaria diagnosis. Relationship between malaria and anaemia is well documented. However, spatial autocorrelation of malaria and anaemia before and after reported interruption of transmission is not well understood. After a reported interruption of transmission in the current study sites between April 2007 and April 2008, new malaria cases have been documented. It is not clear if these cases are newly imported or are representative of an existing transmission reservoir. The study objectives were to: determine the predictive value of fever and/or other malaria symptoms for P. falciparum parasitemia among individuals seeking treatment in highland areas of very low transmission; determine spatial association between anaemia prevalence and previous malaria incidence before and after reported interruption of transmission and; determine if new malaria cases reflect existence of transmission hotspots in highland areas of very low malaria transmission. The study design used both retrospective (2003-2009) and prospective (2010-2012) review and monitoring of clinical, climatic, demographic and entomologic data respectively. A total of 3420 asymptomatic individuals and 1682 households were sampled. Sensitivity, specificity likelihood ratios were analyzed using STATA and R, spatial autocorrelation was determined using ArcGIS and SaTScan while correlation was determined using STATA. Malaria hotspots were determined using ArcGIS and SaTScan. P