| The outbreak of severe diarrhea in swine has caused enormous economic loss in China since 2010. While pathogens contributing to diarrhea are remain elusive and well-established strategies for prevention are urgently needed. In this study we employed a two-year survey(2013~2014) to understand the etiology of diarrhea in China and totally 2,456 samples were collected from 16 provinces including northern, north east, north west and south west China. 63 fecal samples were randomly selected to detect PEDV, TGEV, PRV and PoRV, respectively, using PCR or RT-PCR. Positive samples were further analyzed with Vero cells for isolation of certain viruses and RT-PCR was introduced to discover the variation of S gene in PEDV. Our data indicated that diarrhea still confers huge threat to swine population health even though the overall incidence of diarrhea has fallen slightly. We further observed a higher disease incidence in South west area compared with others and piglets are the major targets of severe diarrhea. Interestingly, most diarrhea occurred during winter and spring seasons and less diarrhea were identified in large swine farms in this study. Based on a clinical investigation, live vaccine works better than killed vaccine to prevent this disease. To date, it is unclear that how many pathogens can lead to severe diarrhea in China despite most cases were caused by virus including PEDV, PoRV, PRV and TGEV. These four pathogens are widely distributed and a combination of two pathogens contributed to most of diseases while incidence for PEDV+PRV can goes up to 9.52%. Finally, 32 PEDV S gene sequences are available to do phylogenetic analysis with 88.5-100% nucleotide identity from each other and 83.5-100% identity in amino acids. Our results demonstrated that GD3 was derived in major branches from traditional strains CV777 and DR13 while other 31 mutant strains were located at G1-1 branch which is a distal branch from original strains. In summary, our study herein described the dynamic distribution of diarrhea in China with a focus on characterizing transmission and evolution of PEDV and there is no doubts that this will contribute to strategies finalization. |
