Comparative epidemiology of porcine circovirus type 3 in pigs with different clinical presentations

Shao-Lun Zhai,Tao Lin,Ben M Hause,Dan Wang,Qin-Ling Chen,He Zhang,Xia Zhou,Dian-Hong Lv,Xiao-Hui Wen,Feng Li,Wen-Kang Wei,Runxia Liu

doi:10.1186/s12985-017-0892-4

Abstract

BackgroundPorcine circovirus type 3 (PCV3), as an emerging circovirus species, was reported to be widely circulating in the United States, China, South Korea and Poland. Previous studies revealed that PCV3 was mainly concentrated in sick animals with respiratory disease, skin disease, reproductive disorders and so on. However, the circulating status of PCV3 in pigs with other clinical presentations (especilly asymptomatic or diarrhea) was not well established.FindingsIn this study, to conduct a comparative epidemiological survey of PCV3, 80 weaned pig serum samples with severe respiratory disease (SRD), 175 weaned pig serum samples with mild respiratory disease (MRD), 216 asymptomatic weaned pig serum samples, 35 diarrheal weaned pig samples and 35 non-diarrheal weaned pig samples were collected from eight provinces of China. Via qPCR testing, PCV3 was circulating in all sampling provinces, with total positive rates varying from 1.04% to 100%. Interestingly, the PCV3-positive rate was significantly higher in weaned pigs with SRD (63.75%, 51/80) than in those weaned pigs with MRD (13.14%, 23/175) and asymptomatic pigs (1.85%, 4/216) (P < 0.01). Similarly, the PCV3-positive rate was significantly higher in diarrheal weaned pigs (17.14%, 6/35) than in non-diarrheal weaned pigs (2.86%, 1/35) (P < 0.05). Moreover, the lower Ct values of qPCR were frequently found in those weaned pigs or fattening pigs with respiratory disease and diarrhea rather than that in asymptomatic pigs. Sequence analysis showed that low genetic diversity existed among those PCV3 sequences collected from pigs with different clinical presentations.ConclusionsThe present study further extends evidence that newly described PCV3 widely circulates in six additional provinces of Southern and Northern China and has high similarity to previously reported isolates. As an emerging virus of swine, although the present case-control study reveals that PCV3 has a potential association with swine respiratory disease and diarrhea, further investigations into the pathogenesis are needed to ascertain the role of PCV3 in swine health.

Highlights

Porcine circovirus type 3 (PCV3), as an emerging circovirus species, was reported to be widely circulating in the United States, China, South Korea and Poland
As an emerging virus of swine, the present case-control study reveals that PCV3 has a potential association with swine respiratory disease and diarrhea, further investigations into the pathogenesis are needed to ascertain the role of PCV3 in swine health
After testing by quantitative PCR (qPCR), PCV3 was circulating in all sampling provinces, with total positive rates of 100% (8/8) in Jilin, 44.29% (62/140) in Guangdong, 7.69% (2/26) in Shandong, 3.75% (6/160) in Gansu, 8.82% (3/34) in Guangxi, 13.85% (9/65) in Sichuan, 1.04% (1/96) in Yunnan and 23.33% (7/30) in Neimenggu, respectively

Summary

Introduction

Porcine circovirus type 3 (PCV3), as an emerging circovirus species, was reported to be widely circulating in the United States, China, South Korea and Poland. Previous studies revealed that PCV3 was mainly concentrated in sick animals with respiratory disease, skin disease, reproductive disorders and so on. The circulating status of PCV3 in pigs with other clinical presentations (especilly asymptomatic or diarrhea) was not well established. Small non-enveloped DNA circoviruses of concern to animal and human health are classified in two genera (Circovirus and Cyclovirus) in the Circoviridae family. PCV1 can infect and replicate in swine, but is not known to cause any obvious disease [2]. PCV2 can cause porcine circovirus disease (PCVD) or porcine circovirusassociated disease (PCVAD), which is characterized by postweaning multisystemic wasting syndrome (PMWS), porcine dermatitis and nephrotic syndrome (PDNS), interstitial pneumonia, and reproductive disorders [5, 6]

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Conclusion