Phylogenetic analysis of porcine circovirus 4 in Henan Province of China: A retrospective study from 2011 to 2021

Abstract

Porcine circovirus 4 (PCV4), a novel circovirus, was first discovered in April 2019 in Hunan Province of China. At present, PCV4 infection has been detected in China and South Korea. However, until 2019, there was little information about its circulating status and genetic characteristics. To further clarify the origin and prevalence of PCV4, a total of 152 clinical samples collected from 49 different swine farms of 15 cities in Henan Province of China from 2011 to 2021 were tested for the presence of PCV4 by qPCR, and the complete genome of PCV4 strains was amplified from the positive samples and sequenced. Among these samples, 45.39% (69/152) were positive for PCV4 and 86.67% (13/15) of the cities and 67.35% (33/49) of the swine farms were positive for PCV4. The genome sequences of 15 PCV4 strains were obtained, of which two PCV4 strains (HN‐ZMD‐201212 and HN‐XX‐201212) were achieved from archival samples in 2012, indicating that PCV4 has been circulating for at least 10 years in Henan Province of China. The phylogenetic analysis showed that 15 PCV4 strains in our study together with PCV4 strain HNU‐AHG1‐2019 were clustered into an identical but separate evolutionary branch, with genomic identity ranging from 98.2% to 98.8%. Our research further provides significant epidemiological information on PCV4 in China, which will help understand the origin and genetic characteristics of this new virus.

Development of a real-time TaqMan PCR assay for the detection of porcine circovirus 4

“…At present, according to research reports, PCV4 has been detected in Hunan, Guangxi, Shaanxi, Henan and Inner Mongolia provinces of China ( 3 , 6 , 13 , 14 , 20 ). This is the first study to report the successful detection of PCV4 in the Sichuan province.…”

Current knowledge on epidemiology and evolution of novel porcine circovirus 4

“…Although PCV4 was discovered in 2019 in the Hunan province of China, retrospective studies demonstrated that PCV4 DNA was present in swine samples collected in 2012 [ 4 ], implying PCV4 has been circulating in pigs for at least a decade. Since 2019, PCV4 has been reported in several provinces of China, including Hunan, Henan, Jiangsu, Anhui, Shanxi, Guangxi, and Inner Mongolia [ 3 , 4 , 10 – 14 ]. Furthermore, PCV4 was also detected in domestic swine in Korea [ 15 , 16 ].…”

“…PCV4 was detected in pigs of various age groups and in several tissues, as co-infections with other pathogens, and with a variety of clinical signs, as summarized in Table 1 . To date, PCV4 genomic DNA has been detected in pigs in several provinces in China, as well as in South Korea, with positive rates ranging from 1.6 to 45.39% [ 4 , 10 ]. PCV4 can infect almost all ages of pigs, including sucking, weanling, and fattening pigs, as well as sows and fetuses [ 4 , 10 , 11 , 15 ].…”

“…To date, PCV4 genomic DNA has been detected in pigs in several provinces in China, as well as in South Korea, with positive rates ranging from 1.6 to 45.39% [ 4 , 10 ]. PCV4 can infect almost all ages of pigs, including sucking, weanling, and fattening pigs, as well as sows and fetuses [ 4 , 10 , 11 , 15 ]. Additionally, PCV4 genome has been detected in sera and other tissues, including heart, liver, spleen, lung, kidney, lymph node, tonsil, intestine, and brain.…”

“…PCV4, a newly emerging circovirus, was first identified in 2019 in Hunan, China, in pigs with several clinical disease syndromes, including respiratory and enteric signs as well as porcine dermatitis nephropathy syndrome (PDNS) [ 3 ]. However, in retrospective studies, PCV4 genomic DNA was detected in swine tissue samples collected in 2012 from Henan, China [ 4 ], with some serum samples collected as early as 2008 from Chinese swine positive for PCV4 antibody [ 5 ]. Therefore, there is evidence that PCV4 has been present and circulating in swine herds for more than a decade.…”