2.1. Sample collection and nucleic acid extraction
The screening for PCV4 was done on 335 samples which were divided into
six groups including aborted fetuses (n = 86), suckling (n = 43), weaner
(n = 135), grower (n = 23), finisher (n = 20) and sow (n = 28). Except
testicles of healthy suckling pigs, which were submitted for herd
monitoring of PRRSV, the other pooled internal organs (lungs, spleen,
heart, kidneys) of dead pigs/ aborted fetuses were sent for detection of
common pathogens of swine. The sampling period was from August- December
2019 and January- August 2020, and covered 36 farms in nine provinces in
South Korea. The samples were homogenized, diluted 10-fold with
phosphate-buffered saline (PBS 0.1M, pH 7.4), then stored at -70℃. The
extraction of total nucleic acid was done using DNA/RNA extraction kit
(iNtRON Biotechnology, Inc. Korea). Afterward, extracted nucleic acid
samples were again stored at -70℃.