Isolation and possibility of vertical transmission of G9P[23] and G12P[7] group A rotavirus strains in pigs.

Background: Porcine group A rotavirus (RVA) is a significant causative agent of diarrhea in piglets, leading to substantial economic losses in pig farms worldwide. While horizontal transmission of RVA among pig populations is well documented, the possibility of vertical transmission from sows to newborn piglets has not been definitively confirmed.

Results: In this study, piglet testicles, umbilical cord blood, and colostrum were collected from porcine RVA (PoRVA)-active farms for analysis. The samples presented high PoRVA-positive rates, with 70.00% in the testicle samples, 55.00% in the umbilical cord blood samples, and 73.33% in the colostrum samples. Immunohistochemical assays confirmed the presence of PoRVA in neonatal piglet testicles. Additionally, two PoRVA strains, RVA/Pig/CHN/QT/2023/G9P [23] (QT2023) and RVA/Pig/CHN/BH/2023/G12P [7] (BH2023), were isolated from newborn piglet testicles. Complete genome analyses revealed that strains QT2023 and BH2023 both presented a Wa-like backbone, with the genotype constellation of G9-P [23]-I5-R1-C1-M1-A8-N1-T1-E1-H1 and G12-P [7]-I5-R1-C1-M1-A8-N1-T1-E1-H1, respectively. While strains QT2023 and BH2023 originated from PoRVAs, sequence identities and phylogenetic analyses suggested close relationships with human rotaviruses in specific genes. Furthermore, successful viral replication of these strains in MA-104 cells was observed. Inoculation of PoRVA-negative piglets with strains QT2023 and BH2023 resulted in clinical diarrhea, fecal virus shedding, and intestinal pathological changes, highlighting the pathogenicity of these strains.

Conclusion: This study provides evidence that PoRVA can breach the placental barrier and spread to newborn piglets through vertical transmission. These discoveries enhance our understanding of the transmission route of porcine RVA and have the potential to guide the development of efficient vaccine strategies for combating this disease.