Viral metagenomics analysis demonstrates the diversity of viral flora in piglet diarrhoeic faeces in China

To investigate the diversity of viral flora, we used metagenomics to study the viral communities in a pooled faecal sample of 27 diarrhoeic piglets from intensive commercial farms in China. The 15 distinct mammalian viruses identified in the pooled diarrhoeic sample were, in order of abundance of nucleic acid sequence, Porcine epidemic diarrhea virus (PEDV), sapovirus, porcine bocavirus-4 (PBoV-4), sapelovirus, torovirus, coronavirus, PBoV-2, stool-associated single-stranded DNA virus (poSCV), astrovirus (AstV), kobuvirus, posavirus-1, porcine enterovirus-9 (PEV-9), porcine circovirus-like (po-circo-like) virus, picobirnavirus (PBV) and Torque teno sus virus 2 (TTSuV-2). The prevalence rate of each virus was verified from diarrhoeic and healthy piglets by PCR assay. A mean of 5.5 different viruses were shed in diarrhoeic piglets, and one piglet was in fact co-infected with 11 different viruses. By contrast, healthy piglets shed a mean of 3.2 different viruses. Compared with samples from healthy piglets, the co-infection of PEDV and PBoV had a high prevalence rate in diarrhoea samples, suggesting a correlation with the appearance of diarrhoea in piglets. Furthermore, we report here for the first time the presence of several recently described viruses in China, and the identification of novel genotypes. Therefore, our investigation results provide an unbiased survey of viral communities and prevalence in faecal samples of piglets.