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 mosquitoesMethods: 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

Serological evidence of exposure to Rift Valley, Dengue and Chikungunya Viruses among agropastoral communities in Manyara and Morogoro regions in Tanzania: A community survey.

Tanzania has recently experienced outbreaks of dengue in two coastal regions of Dar es Salaam and Tanga. Chikungunya and Rift Valley Fever outbreaks have also been recorded in the past decade. Little is known on the burden of the arboviral disease causing viruses (Dengue, Rift Valley and Chikungunya) endemically in the inter-epidemic periods. We aimed at determining the prevalence of the dengue, rift valley and chikungunya among humans in two geo ecologically distinct sites. The community-based cross-sectional study was conducted in Magugu in Manyara region and Wami-Dakawa in Morogoro region in Tanzania. Venous blood was collected from participants of all age groups, serum prepared from samples and subjected to ELISA tests for RVFV IgG/IgM, DENV IgG/IgM, and CHIKV IgM/IgG. Samples that were positive for IgM ELISA tests were subjected to a quantitative RT PCR for each virus. A structured questionnaire was used to collect socio-demographic information. Data analysis was performed by using SPSSv22. A total of 191 individuals from both sites participated in the study. Only one individual was CHIKV seropositive in Magugu, but none was seropositive or positive for either RVFV or DENV. Of the 122 individuals from Wami-Dakawa site, 16.39% (n = 20) had recent exposure to RVFV while 9.83% (n = 12) were seropositive for CHIKV. All samples were negative by RVFV and CHIKV qPCR. Neither infection nor exposure to DENV was observed in participants from both sites. Being more than 5 in a household, having no formal education and having recently travelled to an urban area were risk factors associated with RVFV and CHIKV seropositivity. We report a considerable exposure to RVFV and CHIKV among Wami-Dakawa residents during the dry season and an absence of exposure of the viruses among humans in Magugu site. In both sites, neither DENV exposure nor infection was detected