Epidemiology and vaccine of porcine epidemic diarrhea virus in China: a mini-review

SUN, Dongbo; WANG, Xinyu; WEI, Shan; CHEN, Jianfei; FENG, Li

After the PEDV outbreaks in 2010, detailed studies of the molecular epidemiology and evolution of PEDV were conducted in China, which led to the accumulation of a large amount of data (Table 1) . From February 2011 to March 2014, a long-term investigation showed that PEDV was circulating in 29 provinces in China, excluding Tibet and Hainan (Fig. 1A) ; the positive rates of samples varied from 61.10% to 78.49%, and the positive rates of pig farms varied from 71.43% to 83.47% (Fig. 1B) [10, 45] . The positive rates of PEDV in samples or farms were significantly [20] higher compared with earlier PEDV outbreaks in China and other countries. In addition to the PEDV, swine transmissible gastroenteritis virus, porcine rotavirus, porcine kobuvirus, porcine bocavirus, porcine enterovirus, porcine teschovirus, Lawsonia intracellularis and porcine deltacoronavirus have also been found in diarrhea samples from pigs [10, 12, 44] . These data demonstrated that PED occurred extensively among the pig population in China and that PEDV was the major cause of viral diarrheal diseases in swine during the recent outbreaks. However, co-infections of other intestinal pathogens with PEDV should also be monitored dynamically in future studies in China. The S1 regions of the spike (S) protein-encoding gene of 99 selected PEDV strains were divided into two groups (GI and GII) in a phylogenetic tree. The GI group consists of two subgroups (GIa and GIb), while the GII group also consists of two subgroups (GIIa and GIIb) (Fig. 2 ). Ten Chinese PEDV strains isolated from 2004 to 2015, which exhibited Several reports indicated that for PEDV field strains, the neutralizing epitopes of the major antigenic protein, the S protein, showed high conservation and were highly similar to that of the vaccine strain CV777 [2, 15, 33] . These data suggest that in China, the traditional PEDV vaccine strain (CV777) still could prevent infections by PEDV field strains and provide effective cross-protection. However, the protective effect of the PEDV vaccine needs to be dynamically monitored in future due to the increasing trend of PEDV variants in China.