Surveillance of Vector-Borne Infections (Chikungunya, Dengue, and Malaria) in Bo, Sierra Leone, 2012–2013

Document Type




Publication Date



Malaria remains a significant cause of morbidity and mortality in West Africa, but the contributionof other vector-borne infections (VBIs) to the burden ofdisease has been understudied. We used rapid diagnostictests(RDTs)forthreeVBIstotestbloodsamplesfrom1,795 febrile residents of Bo City, Sierra Leone, over a1-year period in 2012–2013. In total, 24% of the tests were positive for malaria, fewer than 5% were positive formarkers of dengue virus infection, and 39% were positivefor IgM directed against chikungunya virus (CHIKV) or arelated alphavirus. In total, more than half (55%) of thesefebrile individuals tested positive for at least one of thethree VBIs, which highlights the very high burden of vector-borne diseases in this population. The prevalence ofpositives on the Chikungunya IgM and dengue tests did not vary significantly with age (P> 0.36), but higher ratesof malaria were observed in children < 15 years of age (P< 0.001). Positive results on the Chikungunya IgM RDTswere moderately correlated with rainfall (r2= 0.599). Based on the high prevalence of positive results on theChikungunya IgM RDTs from individuals Bo and its environs, there is a need to examine whether an ecologicalshift toward a greater burden from CHIKV or related alphaviruses is occurring in other parts of Sierra Leone or theWest African region