Concurrent Infection With Dengue and Chikungunya Viruses in Humans and Mosquitoes: A Field Survey in Lower Moshi, Tanzania

Introduction: Dengue and Chikungunya have re-emerged as important diseases of global concern. Co-infections with Dengue virus (DENV) and Chikungunya virus (CHIKV) could have serious outcomes if not diagnosed and managed optimally. However, the key focal points for the maintenance of CHIKV and DENV infections and the extent of their co-infection remain poorly understood in many geo-ecologically distinct parts of Tanzania. Objective: We aimed to comparatively examine the prevalence and factors for seropositivity to DENV and CHIKV and their infection rates in humans and mosquitoes Methods: A cross-sectional study was performed in the Lower Moshi area of the Kilimanjaro region from April to July 2020. DENV and CHIKV exposure was determined by detecting IgM to the viruses using enzyme linked immunosorbent assay whereas infection was determined by real time quantitative polymerase chain reaction (RT-qPCR) assay. Results: Insecticide Treated Bed Net (ITN) use (χ2=3.504; p< 0.05), being ≥7 individuals living in the same household (χ2=4.655; p<0.05) and a recent travel to an urban destination (χ2=3.39; p< 0.05) were the only factors associated with CHIKV seropositivity. ITN use was the only factor associated with CHIKV infection (χ2=5.204; p<0.05). A recent travel to an urban destination (χ2=4.401; p< 0.05) was the only factor associated with DENV seropositivity. Five (1.5%) Ae. aegypti pools were positive for CHIKV whereas 1 (0.3%) was positive for DENV. Two Cx. pipiens, pools (1.9%) were positive for CHIKV. None of the Cx. pipiens mosquitoes was positive for DENV. No associations between DENV and CHIKV seropositivity was observed in humans but DENV infection was strongly associated with CHIKV infection (χ2 = 238.45; p<0.01). CHIKV infection was observed to be consistently higher in both, humans and mosquitoes. Conclusion: Detection of DENV and CHIKV in both humans and vector mosquitoes confirms that both viruses are actively circulating in the Lower Moshi area of Kilimanjaro region in Tanzania. Our findings point out the Lower Moshi area as a potential focal point for the maintenance of the two viruses and possibly other vector borne viruses. We call upon sustained active surveillance of arboviruses and other re-emerging infections to be better prepared for possible outbreaks by the viruses.