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Outbreaks of diarrhea in newborn piglets without detection of transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus (PDCoV), have been recorded in a pig farm in southern China since February 2017. Isolation and propagation of the pathogen in cell culture resulted in discovery of a novel swine enteric alphacoronavirus (tentatively named SeACoV) related to the bat coronavirus HKU2 identified in the same region a decade ago. Specific fluorescence signal was detected in Vero cells infected with SeACoV by using a positive sow serum collected in the same farm, but not by using TGEV-, PEDV- or PDCoV-specific antibody. Electron microscopy observation demonstrated that the virus particle with surface projections was 100–120 nm in diameter. Complete genomic sequencing and analyses of SeACoV indicated that the extreme amino-terminal domain of the SeACoV spike (S) glycoprotein structurally similar to the domain 0 of the alphacoronavirus NL63, whereas the rest part of S structurally resembles domains B to D of the betacoronavirus. The SeACoV-S domain 0 associated with enteric tropism had an extremely high variability, harboring 75-amino-acid (aa) substitutions and a 2-aa insertion, compared to that of HKU2, which is likely responsible for the extended host range or cross-species transmission.
The isolated virus was infectious in pigs when inoculated orally into 3-day-old newborn piglets, leading to clinical signs of diarrhea and fecal virus shedding.
These results confirmed that it is a novel swine enteric coronavirus representing the fifth porcine coronavirus.
Yongfei Pan, Xiaoyan Tian, Pan Qin, Bin Wang, Pengwei Zhao, Yong-Le Yang, Lianxiang Wang, Dongdong Wang, Yanhua Song, Xiangbin Zhang, Yao-Wei Huang. Discovery of a novel swine enteric alphacoronavirus (SeACoV) in southern China. Veterinary Microbiology 211 (2017) 15–21. http://dx.doi.org/10.1016/j.vetmic.2017.09.020
