A first report of rotavirus B from Zambian pigs leading to the discovery of a novel VP4 genotype P[9].

Background: Rotavirus B (RVB) causes diarrhea in humans and pigs. Although various RVB strains were identified in humans and various animals globally, little is known about the epidemiology RVB infection in Africa. In this study, we attempted to examine the prevalence of RVB infection in pig populations in Zambia.

Methods: Metagenomic analyses were conducted on pig feces collected in Zambia to detect double stranded RNA viruses, including RVB. To clarify the prevalence of RVB infection in pig populations in Zambia, 147 fecal samples were screened for the RVB detection by RT-qPCR. Full genome sequence of a detected RVB was determined by Sanger sequencing and genetically analyzed.

Results: The metagenomic analyses revealed that RVB sequence reads and contigs of RVB were detected from one fecal sample collected from pigs in Zambia. RT-qPCR screening detected RVB genomes in 36.7% (54/147) of fecal samples. Among 54 positive samples, 13 were positive in non-diarrheal samples (n = 48, 27.1%) and 41 in diarrheal samples (n = 99, 41.4%). Genetic analyses demonstrated that all the segments of ZP18-18, except for VP4, had high nucleotide sequence identities (80.6-92.6%) with all other known RVB strains detected in pigs. In contrast, the VP4 sequence of ZP18-18 was highly divergent from other RVB strains (< 64.6% identities) and formed a distinct lineage in the phylogenetic tree. Notably, the VP8 subunit of the VP4 showed remarkably low amino acid identities (33.3%) to those of known RVB strains, indicating that the VP8 subunit of ZP18-18 was unique among RVB strains. According to the whole genome classification for RVB, ZP18-18 was assigned to a genotype constellation, G18-P[9]-I12-R4-C4-M4-A8-N10-T5-E4-H7 with the newly established VP4 genotype P[9].

Conclusions: This current study updates the geographical distribution and the genetic diversity of RVB. Given the lack of information regarding RVB in Africa, further RVB surveillance is required to assess the potential risk to humans and animals.