The large-scale outbreaks of severe diarrhea caused by viruses have occurred in pigs since 2010, resulting in great damage to the pig industry. However, multiple infections have contributed to the outbreak of the disease and also resulted in great difficulties in diagnosis and control of the disease. Thus, a Luminex xTAG multiplex detection method, which was more sensitive and specific than general multiplex PCR method, was developed for the detection of 11 viral diarrhea pathogens, including PKoV, PAstV, PEDV, PSaV, PSV, PTV, PDCoV, TGEV, BVDV, PoRV, and PToV. To investigate the prevalence of diarrhea-associated viruses responsible for the outbreaks, a total of 753 porcine stool specimens collected from 9 pig farms in Shanghai during 2015–2018 were tested and the pathogen spectrums and co-infections were analyzed. As a result, PKoV, PAstV and PEDV were most commonly detected viruses in diarrheal pigs with the rate of 38.65% (291/753), 20.32% (153/753), and 15.54% (117/753), respectively. Furthermore, multiple infections were commonly seen, with positive rate of 28.42%. Infection pattern of the viral diarrhea pathogens in a specific farm was changing, and different farms had the various diarrhea infection patterns. A longitudinal investigation showed that PEDV was the key pathogen which was closely related to the death of diarrhea piglets. Other pathogens might play synergistic roles in the pathogenesis of diarrhea disease. Furthermore, the surveillance confirmed that variant enteropathogenic viruses were leading etiologic agents of porcine diarrhea, either mono-infection or co-infections of PKoV were common in pigs in Shanghai, but PEDV was still the key pathogen and multiple pathogens synergistically complicated the infection status, suggesting that controlling porcine diarrhea might be more complex than previously thought. The study provides a better understanding of diarrhea viruses in piglets, which will aid in better preventing and controlling epidemics of viral porcine diarrhea.

Porcine epidemic diarrhea virus (PEDV) is prevalent in most parts of the world. Owing to its antigenic variation, prevention of the diseases caused by this virus is difficult. In this study, two PEDV isolates with similar growth kinetics were successfully propagated in Vero cells. Complete genome sequence analysis showed that they have a 49nt deletion in the ORF3 gene and were classified into Group 1, the same group that includes the classical CV777 strain. Recombination analysis revealed that the event had occurred in the ORF1a gene, at 3596-6819 nt, among the two PEDV isolates and the CV777 and DR13 strains. During their continuous propagation, 14 nonsynonymous mutations occurred in the spike (S) gene of strain JS-2/2014 between generations G5 and G90, but there were no changes between G90 and G100. We assumed that strain JS-2/2014 might be attenuated by the 90th generation. Piglets orally fed with JS-2/2014 G90 showed no clinical symptoms, and no virus was detected in the feces and nasal fluid. In conclusion, JS-2/2014 was successfully identified by screening, was attenuated after propagation in Vero cells, and may serve as a candidate virus for vaccine preparations.

BackgroundPorcine sapelovirus (PSV) infections have been associated with a wide spectrum of symptoms ranging from asymptomatic infection to clinical signs including diarrhoea, pneumonia, reproductive disorders, and polioencephalomyelitis. Although it has a global distribution, studies on PSV in domestic have been relatively few so far which goes against for this pathogen's research and disease prevention. MethodsIn this study, we isolated a PSV strain, SHCM2019, from the swine faecal specimens with PK-15 cells. To investigate its molecular characteristics and pathogenicity, the genomic sequence of the SHCM2019 strain was analysed, and further the clinical manifestations and pathological changes exhibited following inoculation of the neonatal piglets were observed. ResultsThe strain isolated with PK-15 cells, was identi ed as PSV by RT-PCR, IFA and TEM assays. Sequencing results showed that the full-length genome of the SHCM2019 strain was 7567 nucleotides including a 27nucloetude poly (A) tail. Phylogenetic analysis demonstrated that the virus isolate belonged to PSV and was classi ed into the Chinese strain cluster. Virus recombination analysis indicated that there might be a recombination break point upstream of the 3D region in PSVs. Pathogenicity research demonstrated that the virus isolate could cause diarrhoea and pneumonia in piglets. ConclusionThis study presented the isolation of a recombinant PSV strain, SHCM2019, and demonstrated the isolate was pathogenic. Our results may provide a reference for future researches of the pathogenic mechanism and evolutionary characteristics of PSV.