Molecular epidemiology of rotaviruses in Northwest Ethiopia after national vaccine introduction

Abstract

Background: Rotaviruses mortality among infants and young children is high in Sub-Saharan Africa. Recently, Ethiopia introduced the monovalent rotavirus vaccine in its national immunization program to decrease the burden of rotavirus disease and mortality. Rotavirus surveillance in Ethiopia is based largely on data provided by sentinel hospitals in its capital Addis Ababa.

Objective: To assess rotavirus abundancy and diversity in outpatient infants and children outside of Addis Ababa in the early post-introduction period.

Method: Fecal samples were obtained from children aged less than five years presenting with diarrhea at outpatient health institutions in two cities in Northwest Ethiopia, Gondar and Bahir Dar, from November 2015 to April 2016. Basic demographic data were assessed. Real-time RT-PCR was used to detect rotavirus A RNA. Based on sequences of VP4 and VP7 gene segments phylogenetic analysis was performed.

Results: Rotavirus wildtype positivity was 25% (113/450). Rotavirus infection was less common in infants below 6 months than in children of all other age-groups. Rotavirus genotype distributions were distinct between Bahir Dar and Gondar. In total, wildtype G3P[8], G2P[4], G9P[8], G12P[8], and G3P[6] rotaviruses were detected in 68 (60.2%), 21 (18.6%), 13 (11.5%), 9 (8.0%), and 2 (1.8%) of the positive samples, respectively. Wildtype G1P[8] strains were absent. The phylogenetic analysis revealed close relatedness of current rotaviruses with Ethiopian strains of the pre-vaccination period.

Conclusion: In the early period after the introduction of vaccination, rotaviruses in Northwestern Ethiopia were frequent in children of 6-59 months and diverse. High phylogenetic relatedness with strains of the pre-vaccine era, indicate absence of early vaccine-induced strain replacement. Future surveillance studies should be carried out throughout the country to gain comprehensive data on rotavirus strain diversity and to monitor the effect of the ongoing vaccine program on the disease burden and eventual rotavirus strain replacement.

Keywords: Childhood diarrhea; Low-income country; Molecular epidemiology; Northwest Ethiopia; Rotavirus genotype; Vaccination.