Serological evidence of exposure to Rift Valley, Dengue and Chikungunya Viruses among agropastoral communities in Manyara and Morogoro regions in Tanzania: A community Survey
Authors: Budodo Rule M. , Horumpende Pius G. , Mkumbaye Sixbert I. , Mmbaga Blandina T. , Mwakapuja Richard S. , Chilongola Jaffu O. 
Published: January 2020

Introduction

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.

Methodology

The community-based cross-sectional study was conducted in Magugu in Manyara region and Mvomero 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 conducted using SPSSv22.

Results

A total of 191 individuals from both sites participated in the study. Only one CHIKV was detected in Magugu site but none of the 69 participants from Magugu site was seropositive or positive for RVFV and DENV. Of the 122 individuals from Wami-Dakawa site, 16.39% (n=20) had recent exposure to RVFV while 9.83% (n=12) were recently infected by Chikungunya virus. All samples were negative by RVFV and CHIKV qPCR. Neither Infection nor exposure to DENV was observed in participants from Wami-Dakawa. Risk factors associated with RVFV and DCHIKV seropositivity were being more than 5 in a household, having no formal education and having recently travelled to an urban area.

Conclusion

We report an active circulation of RVFV and CHIKV in humans in Wami-Dakawa, in Mvomero district of Morogoro region during dry season, a higher rate of exposure to RVFV compared to CHIKV and an absence of circulating RVFV, DENV and CHIKV in humans in Magugu site in Manyara region.

Author Summary

Dengue, Chikungunya, rift valley and other viruses constitute an important group of etiologies of fever in Tanzania. In the past decade, Tanzania has experienced DENV and RVFV at different times. While RVFV outbreaks have occurred cyclically in approximately ten-year periods in Tanzania, DENV outbreaks have been more frequent since 2010. CHIKV infection is an important but largely unrecognized illness in Tanzania. In this study, we aimed to generate baseline data on the exposure and infection status of DENV, RVFV and CHIKV by detecting antibodies to the viruses and detecting the viruses in human subjects in two geo-ecological distinct sites. Neither infection nor exposure to the viruses were in observed in Magugu site in Manyara region, northern Tanzania. There was a significant exposure to RVFV (16.39%) and CHIKV (9.83%) in Wami-Dakawa but not to DENV in either site. None of the viruses was detected by PCR in any of the sites. Potential risks for exposure to CHIKV and RVFV were Larger numbers of household members, having no formal education and having recently travelled to an urban destination. Since arbovirus outbreaks are usually unpredictable, it is crucial to undertake active surveillance for RVFV, DENV, CHIKV and other viral agents in Tanzania.