Molecular surveillance and genetic divergence of rotavirus A antigenic epitopes in Gabonese children with acute gastroenteritis.

BACKGROUND: Rotavirus A (RVA) causes acute gastroenteritis in children <5 years of age in sub-Saharan Africa. In this study, we described the epidemiology and genetic diversity of RVA infecting Gabonese children and examined the antigenic variability of circulating strains in relation to available vaccine strains to maximize the public health benefits of introducing rotavirus vaccine through the Expanded Programme on Immunization (EPI) in Gabon. METHODS: Stool samples were collected consecutively between April 2018 and November 2019 from all hospitalized children <5 years with gastroenteritis and community controls without gastroenteritis. Children were tested for rotavirus A by quantitative RT-PCR and subsequently sequenced to identify circulating rotavirus A genotypes in the most vulnerable population. The VP7 and VP4 (VP8*) antigenic epitopes were mapped to homologs of vaccine strains to assess structural variability and potential impact on antigenicity. FINDINGS: Infections were mostly acquired during the dry season. Rotavirus A was detected in 98/177 (55%) hospitalized children with gastroenteritis and 14/67 (21%) of the control children. The most common RVA genotypes were G1 (18%), G3 (12%), G8 (18%), G9 (2%), G12 (25%), with G8 and G9 reported for the first time in Gabon. All were associated either with P[6] (31%) or P[8] (38%) genotypes. Several non-synonymous substitutions were observed in the antigenic epitopes of VP7 (positions 94 and 147) and VP8* (positions 89, 116, 146 and 150), which may modulate the elicited immune responses. INTERPRETATION: This study contributes to the epidemiological surveillance of rotavirus A required before the introduction of rotavirus vaccination in the EPI for Gabonese children.

Prevalence of Pathogens in Young Children Presenting to Hospital with Diarrhea from Lambaréné, Gabon.

Diarrheal disease is the second most frequent cause of mortality in children younger than 5 years worldwide, causing more than half a million deaths each year. Our knowledge of the epidemiology of potentially pathogenic agents found in children suffering from diarrhea in sub-Saharan African countries is still patchy, and thereby hinders implementation of effective preventative interventions. The lack of cheap, easy-to-use diagnostic tools leads to mostly symptomatic and empirical case management. An observational study with a total of 241 participants was conducted from February 2017 to August 2018 among children younger than 5 years with diarrhea in Lambaréné, Gabon. Clinical and demographic data were recorded, and a stool sample was collected. The samples were examined using a commercial rapid immunoassay to detect Rotavirus/adenovirus, conventional bacterial culture for Salmonella spp., and multiplex real-time PCR for Cryptosporidium spp., Giardia lamblia, Cyclospora cayetanensis, enterotoxigenic Escherichia coli (ETEC), and enteroinvasive Escherichia coli (EIEC)/Shigella. At least one infectious agent was present in 121 of 241 (50%) samples. The most frequently isolated pathogens were EIEC/Shigella and ETEC (54/179; 30.2% and 44/179; 24.6%, respectively), followed by G. lamblia (33/241; 13.7%), Cryptosporidium spp. (31/241; 12.9%), and Rotavirus (23/241; 9.5%). Coinfection with multiple pathogens was observed in 33% (40/121) of the positive cases with EIEC/Shigella, ETEC, and Cryptosporidium spp. most frequently identified. Our results provide new insight into the possible causes of diarrheal disease in the Moyen-Ogooué region of Gabon and motivate further research on possible modes of infection and targeted preventive measures.