2.1 Sample information
From 2015 to 2019, tissue samples (n = 93) and serum samples (n = 164) of pigs were collected from 15 swine farms in Nanning, Guilin, Fangchenggang, Beihai, Baise, and Hezhou in Guangxi Province, China (Figure 1). Of these, 17 tissue samples and 11 serum samples were from swine with severe clinical signs, including respiratory disease, lymphadenopathy and PDNS. This study received animal ethics approval (No. Xidakezi2000138) from Guangxi University (see ethics approval and consent to participate).