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

Abstract

25Introduction: Tanzania has recently experienced outbreaks of dengue in two coastal regions of 26 Dar es Salaam and Tanga. Chikungunya and Rift Valley Fever outbreaks have also been recorded 27 in the past decade. Little is known on the burden of the arboviral disease causing viruses (Dengue, 28 Rift Valley and Chikungunya) endemically in the inter-epidemic periods. We aimed at determining 29 the prevalence of the dengue, rift valley and chikungunya among humans in two geo ecologically 30 distinct sites. 31 Methodology: The community-based cross-sectional study was conducted in Magugu in Manyara 32 region and Mvomero in Morogoro region in Tanzania. Venous blood was collected from 33 participants of all age groups, serum prepared from samples and subjected to ELISA tests for 34 RVFV IgG/IgM, DENV IgG/IgM, and CHIKV IgM/IgG. Samples that were positive for IgM ELISA tests 35 were subjected to a quantitative RT PCR for each virus. A structured questionnaire was used to 36 collect socio-demographic information. Data analysis was conducted using SPSSv22. 37 Results: A total of 191 individuals from both sites participated in the study. Only one CHIKV was 38 detected in Magugu site but none of the 69 participants from Magugu site was seropositive or 39 positive for RVFV and DENV. Of the 122 individuals from Wami-Dakawa site, 16.39% (n=20) had 40 recent exposure to RVFV while 9.83% (n=12) were recently infected by Chikungunya virus. All 41 samples were negative by RVFV and CHIKV qPCR. Neither Infection nor exposure to DENV was 42 observed in participants from Wami-Dakawa. Risk factors associated with RVFV and DCHIKV 43 seropositivity were being more than 5 in a household, having no formal education and having 44 recently travelled to an urban area. 3 45 Conclusion: We report an active circulation of RVFV and CHIKV in humans in Wami-Dakawa, in 46 Mvomero district of Morogoro region during dry season, a higher rate of exposure to RVFV 47 compared to CHIKV and an absence of circulating RVFV, DENV and CHIKV in humans in Magugu 48 site in Manyara region. 49 50 Author Summary 53 Dengue, Chikungunya, rift valley and other viruses constitute an important group of etiologies of 54 fever in Tanzania. In the past decade, Tanzania has experienced DENV and RVFV at different 55 times. While RVFV outbreaks have occurred cyclically in approximately ten-year periods in 56 Tanzania, DENV outbreaks have been more frequent since 2010. CHIKV infection is an important 57 but largely unrecognized illness in Tanzania. In this study, we aimed to generate baseline data on 58 the exposure and infection status of DENV, RVFV and CHIKV by detecting antibodies to the viruses 59 and detecting the viruses in human subjects in two geo-ecological distinct sites. Neither infection 60 nor exposure to the viruses were in observed in Magugu site in Manyara region, northern 61 Tanzania. There was a significant exposure to RVFV (16.39%) and CHIKV (9.83%) in Wami-Dakawa 62 but not to DENV in either site. None of the viruses was detected by PCR in any ...

Seroprevalence and associated risk factors of selected zoonotic viral hemorrhagic fevers in Tanzania

“…A significantly high proportion of YF, EVD and MVD seropositivity identified in our study expressed selected VHF group specificity, reacting with YF, MBV, and EVD strains. The observed seropositivity of EVD and MBV in our study support those reported elsewhere in Africa in the absence of severe clinical manifestations associated with asymptomatic or mild infections, suggesting subclinical forms of the diseases (Boisen et al, 2015;Brainard et al, 2016;Budodo et al, 2020). Similar low prevalence of VHF (including Yellow fever virus, Marburg virus, EVD virus) has been reported in Ethiopia and Uganda (Tsegaye et al, 2018;Nyakarahuka et al, 2020).…”

Detection of Rift Valley Fever virus inter-epidemic activity in Kilimanjaro Region, North Eastern Tanzania

“…aegypti to be more susceptible to RVFV infection compared with other known RVFV vectors. Evidence for RVFV transmission during IEPs has previously been reported among humans, livestock, and wild animals in Tanzania and elsewhere [ 1–4 , 6 , 23 , 30 , 32–35 , 37 , 42 , 45–48 ].…”

“…Validation tests for the test kit have shown a sensitivity of between 91% and 100% and a specificity of 100% [ 28 ]. The cELISA was performed according to the instructions of the manufacturer and as described previously [ 29 , 30 ]. To control the validity of each plate, the mean value of the two negative controls (OD NC ) was computed whereby a plate was considered valid if the OD NC was >0.7.…”

Detection of Rift Valley Fever Virus Interepidemic Activity in Lower Moshi area of Kilimanjaro Region, North Eastern Tanzania: A Community Survey

“…Validation tests for the test kit have shown a sensitivity of between 91 and 100% and a speci city of 100%. The cELISA was performed according to the instructions of the manufacturer and as described previously [23,24]. To control the validity of each plate, the mean value of the two negative controls (OD NC ) was computed whereby a plate was considered valid if the OD NC was>0.7.…”