Severe Diarrhea Outbreaks in Newborn Piglets in China Associated With Porcine Rotavirus B.

Rotavirus B (RVB) is among the enteric pathogens that can cause gastroenteritis in humans and various animals. However, severe diarrhea in newborn piglets has rarely been reported to be linked to porcine RVB (PoRVB). From 2023 to 2024, outbreaks of newborn piglet diarrhea with 20%-50% morbidity and 4%-10% mortality occurred in three herds situated in Anhui, Liaoning, and Jilin provinces of China. Notably, all samples from these herds tested negative for porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), PoRVA and transmissible gastroenteritis virus (TGEV). To identify the causative pathogens of the severe diarrhea in newborn piglets, high-throughput sequencing (HTS) was performed on pooled and individual samples collected from each farm. The results revealed that there were 783,546-1,237,231 mammalian virus reads per pooled sample, with PoRVB being the overwhelmingly dominant virus. A high prevalence of PoRVB (83.3%-100%) was detected in all the affected farms, indicating the association between PoRVB strains and the outbreak of severe piglet diarrhea in the sampled farms. Analysis of de novo assembled whole genomes from individual samples revealed that the PoRVB strains AHLW1/2023, JLCG2/2024, and LNDC5/2024 exhibited 81.8%-95.6% nucleotide and 88.9%-99.0% amino acid sequence identities of all 11 gene segments when compared to the most similar reference PoRVB strains. The genotype constellation of AHLW1/2023 was assigned to G34-P[4]-I13-R4-C4-M7-A8-N10-T4-E4-H7, which differs from JLCG2/2024 by one genotype (R7) and from LNDC5/2024 by three genotypes (G16, R7, and M4). This study demonstrated that PoRVB is the primary etiological agent responsible for severe diarrheal outbreaks in newborn piglets. It also highlights the importance of conducting continuous surveillance to effectively control PoRVB infections.