Sero-prevalence of yellow fever and related Flavi viruses in Ethiopia: a public health perspective

Abstract

BackgroundYellow fever (YF) is a viral hemorrhagic fever, endemic in the tropical forests of Africa and Central and South America. The disease is transmitted by mosquitoes infected with the yellow fever virus (YFV). Ethiopia was affected by the largest YF outbreak since the vaccination era during 1960–1962. The recent YF outbreak occurred in 2013 in Southern part of the country. The current survey of was carried out to determine the YF seroprevalence so as to make recommendations from YF prevention and control in Ethiopia.MethodologyA multistage cluster design was utilized. Consequently, the country was divided into 5 ecological zones and two sampling towns were picked per zone randomly. A total of 1643 serum samples were collected from human participants. The serum samples were tested for IgG antibody against YFV using ELISA. Any serum sample testing positive by ELISA was confirmed by plaque reduction neutralization test (PRNT). In addition, differential testing was performed for other flaviviruses, namely dengue, Zika and West Nile viruses.ResultOf the total samples tested, 10 (0.61%) were confirmed to be IgG positive against YFV and confirmed with PRNT. Nine (0.5%) samples were antibody positive for dengue virus, 15(0.9%) forWest Nile virus and 7 (0.4%) for Zika virus by PRNT. Three out of the five ecological zones namely zones 1, 3 and 5 showed low levels (< 2%) of IgG positivity against YFV. A total of 41(2.5%) cases were confirmed to be positive for one of flaviviruses tested.ConclusionBased on the seroprevalence data, the level of YFV activity and the risk of a YF epidemic in Ethiopia are low. However additional factors that could impact the likelihood of such an epidemic occurring should be considered before making final recommendations for YF prevention and control in Ethiopia. Based on the results of the serosurvey and other YF epidemic risk factors considered, a preventive mass vaccination campaign is not recommended, however the introduction of YF vaccine in routine EPI is proposed nationwide, along with strong laboratory based YF surveillance.

Community-based sero-prevalence of chikungunya and yellow fever in the South Omo Valley of Southern Ethiopia

“…However, the observed overall sero-prevalence (49.5%) of IgG antibody against YFV was low compared to the results of other sero-prevalence studies conducted in YF vaccinated populations in Sudan [32], Brazil [33] and other country [34]. On the other hand, the sero-prevalence against YFV in our study was still higher than the national pooled sero-prevalence of Ethiopia [35] and Western Kenya [19]. These geographic based https://doi.org/10.1371/journal.pntd.0008549.g003…”

“…Previous studies in rural Kenya [20], Senegal [27], Tanzania [39], Bangladesh [40] and Singapore [25] reported a higher percentage of sero-prevalence of IgG antibody against many arboviruses including YFV in older individuals. Previous study in Ethiopia also showed a higher sero-prevalence of IgG antibody to YFV in individuals in the age category of 40-64 years [35]. A similar trend was also observed in the current study.…”

Dengue and Chikungunya among Febrile Outpatients in Kinshasa, Democratic Republic of Congo: a cross-sectional study

“…Since YFV vaccination is an expected cause of cross-reactions, we performed PRNT for DENV and YFV in a subset of samples, and found that the congruence between DENV ELISA and PRNT was lower than in American and Asian settings (33)(34)(35)(36)(37). A similar observation was made in another study in DRC with a certain level of discordance between ELISA and PRNT (38), and in a study in Ethiopia where crossreaction and low confirmation by PRNT was also shown (39). In our study, the majority of the samples negative with DENV PRNT was also negative with PRNT for YFV, which indicates that the high flavivirus IgG positivity was not due to YFV vaccination.…”

Yellow fever and orthotopic liver transplantation: new insights from the autopsy room for an old but re‐emerging disease

“…At the DAP‐HCFMUSP, after deparaffinisation and heat‐induced epitope retrieval, liver, kidney, pancreas, heart, spleen and testis sections were incubated for 18 h overnight with the primary antibody at 4°C. The primary antibody employed was a goat anti‐human immunoglobulin (Ig)M polyclonal anti‐YFV antigen provided by Institute Pasteur‐Dakar, originally standardised for enzyme‐linked immunosorbent assay (ELISA) and validated at the optimised dilution of 1:20 000 with positive and negative controls . Amplification of the reaction was achieved by the polymer molecules conjugated to peroxidase [Reveal – Biotin‐Free Polyvalent horseradish peroxidase diaminobenzidine (HRP DAB); Spring Bioscience, Pleasanton, CA, USA, code SPD‐125] and chromogen (Dako Liquid DAB (DAB) + substrate chromogen system; Dako, Carpenteria, CA, USA, code K3460).…”