Chikungunya and West Nile viruses among blood donors in Rwanda: seroprevalence and distribution of mosquito vectors

Abstract

Introduction : Chikungunya virus (CHIKV) and West Nile viruses (WNV) have natural sylvatic cycles, but may move to cities to infect humans and cause epidemics with serious clinical problems. Nodata exist concerning their seroprevalence in Rwanda, despite their origin from its neighboring countries, Tanzania and Uganda. Here we report a sero-surveillance study of CHIKV and WNV and the regional distribution of their mosquito-vectors in Rwanda. Methods : Rwandan blood donors (n = 874) and Swedish (n = 199) were tested for IgG specific ELISA against CHIKV, using an in-house antigen, the E1 envelope protein, and against WNV using an ELISA commercial kit, FOCUS Diagnostics (Cypress, CA USA). Also data from Rwanda Biomedical Center on assessment of Yellow Fever virus circulation in Rwanda reported in 2014 were collected. Results : seroprevalence of CHIKV IgG was high in Rwanda (47%) compared to Sweden (4.5%), while WNV seroprevalence was 10.4% and 14.1% respectively in Rwanda and Sweden. In the latter group, 78.6% of WNV specific-IgG positive subjects were cross-reactive to Tick Borne Encephalitis virus (TBE), explaining the unexpected seroprevalence of WNV in Sweden. Regarding mosquito-vectors the Culex spp was most prevalent (82.5%) while Aedes spp was found at lower amounts (9.6%) around all Rwanda. Conclusion : in Rwanda, CHIKV is more sero-prevalent as compared to WNV, while the mosquito-vector Culex spp, and is more prevalent followed by Aedes spp. There is a high and bidirectional cross-reactivity between TBE and WNV IgG. The Eastern region of Rwanda reported the highest seroprevalence to CHIKV and WNV, and population of mosquito-vectors.