Dupont K, Nielsen E O, Baekbo P, Larsen L E
National Veterinary Institute, The Technical University of Denmark, Denmark.
Vet Microbiol. 2008 Apr 1;128(1-2):56-64. doi: 10.1016/j.vetmic.2007.09.016. Epub 2007 Oct 2.
Porcine circovirus type 2 (PCV2) is the primary cause of Postweaning Multisystemic Wasting Syndrome (PMWS) in pigs. PCV2, however, is found in both PMWS-affected herds and non-affected herds. The objective of this study was to clarify if PCV2 genome nucleotide sequences isolated from pigs from PMWS-affected herds and non-affected herds cluster phylogenetically in two separate groups. All isolates (45) belonged to PCV2 group 1 and shared a nucleotide sequence identity of 99.4-100% indicating a very homogeneous PCV2 population in Denmark. Phylogenetic analysis of the PCV2 isolates revealed no distinctive clustering of case- and control-herds suggesting that there is no link between PCV2 sequences and herd disease status. The appearance of only PCV2 group 1 isolates in this study (isolates from 2003/2004) led us to determine if PCV2 nucleotide sequences had changed in Denmark over time. Interestingly, all PCV2 isolates from before the first outbreak of PMWS (2001) belonged either to a new PCV2 group identified for the first time in this study and named group 3 (isolates from 1980, 1987 and 1990) or PCV2 group 2 (isolates from 1993 and 1996). The shift from PCV2 group 2 to 1 was confirmed on a more global scale by placing all full genome PCV2 sequences submitted to GenBank from 1997 to 2006 in either of the groups by phylogenetic analysis. The analysis showed that the shift happened in 2003 or even earlier. This may indicate that PCV2 group 1 is a more adapted form of PCV2 and possibly could be more pathogenic.
猪圆环病毒2型（PCV2）是猪断奶后多系统消耗综合征（PMWS）的主要病因。然而，在受PMWS影响的猪群和未受影响的猪群中均发现了PCV2。本研究的目的是阐明从受PMWS影响的猪群和未受影响的猪群中分离出的PCV2基因组核苷酸序列在系统发育上是否聚类为两个独立的组。所有分离株（45株）均属于PCV2第1组，核苷酸序列同一性为99.4-100%，表明丹麦的PCV2群体非常均匀。对PCV2分离株的系统发育分析显示，病例组和对照组猪群没有明显的聚类，这表明PCV2序列与猪群疾病状态之间没有联系。本研究（2003/2004年的分离株）中仅出现了PCV2第1组分离株，这促使我们确定丹麦的PCV2核苷酸序列是否随时间发生了变化。有趣的是，在PMWS首次爆发（2001年）之前的所有PCV2分离株要么属于本研究首次鉴定的一个新的PCV2组，命名为第3组（1980年、1987年和1990年的分离株），要么属于PCV2第2组（1993年和1996年的分离株）。通过对1997年至2006年提交给GenBank的所有PCV2全基因组序列进行系统发育分析，将其归入这两个组中的一个，在更广泛的范围内证实了从PCV2第2组到第1组的转变。分析表明，这种转变发生在2003年甚至更早。这可能表明PCV2第1组是PCV2更适应的形式，可能更具致病性。
