Gagnon Carl A, Tremblay Donald, Tijssen Peter, Venne Marie-Hélène, Houde Alain, Elahi Seyyed Mehdy
Service de diagnostic, Université de Montréal, St-Hyacinthe, Québec.
Can Vet J. 2007 Aug;48(8):811-9.
Since late 2004, the swine industry in the province of Quebec has experienced a significant increase in death rate related to postweaning multisystemic wasting syndrome (PMWS). To explain this phenomenon, 2 hypotheses were formulated: 1) the presence of a 2nd pathogen could be exacerbating the porcine circovirus 2 (PCV-2) infection, or 2) a new and more virulent PCV-2 strain could be infecting swine. In 2005, 13 PMWS cases were submitted to the Quebec provincial diagnostic laboratory and PCV-2 was the only virus that could be found consistently by PCR in all 13 samples. The PCR detection results obtained for other viruses revealed the following: 61.5% were positive for porcine reproductive and respiratory syndrome virus, 30.8% for swine influenza virus, 15.4% for porcine parvovirus, 69.2% for swine torque teno virus (swTTV), 38.5% for swine hepatitis E virus (swHEV) and 84.6% for Mycoplasma hyorhinis; transmissible gastroenteritis virus and porcine respiratory coronavirus (TGEV/PRCV) was not detected. Sequences of the entire genome revealed that these PCV-2 strains belonged to a genotype (named PCV-2b) that has never been reported in Canada. Further sequence analyses on 83 other Canadian PCV-2 positive cases submitted to the provincial diagnostic laboratory during years 2005 and 2006 showed that 79.5% of the viral sequences obtained clustered in the PCV-2b genotype. The appearance of the PCV-2b genotype in Canada may explain the death rate increase related to PMWS, but this relationship has to be confirmed.
自2004年末以来，魁北克省的养猪业因断奶后多系统消耗综合征（PMWS）导致的死亡率显著上升。为解释这一现象，提出了两种假设：1）第二种病原体的存在可能会加剧猪圆环病毒2型（PCV - 2）感染；2）一种新的、毒性更强的PCV - 2毒株可能正在感染猪群。2005年，13例PMWS病例被提交至魁北克省诊断实验室，通过聚合酶链反应（PCR）在所有13个样本中始终能检测到的唯一病毒是PCV - 2。对其他病毒的PCR检测结果如下：猪繁殖与呼吸综合征病毒阳性率为61.5%，猪流感病毒为30.8%，猪细小病毒为15.4%，猪圆环病毒（swTTV）为69.2%，猪戊型肝炎病毒（swHEV）为38.5%，猪鼻支原体为84.6%；未检测到传染性胃肠炎病毒和猪呼吸道冠状病毒（TGEV/PRCV）。全基因组序列显示，这些PCV - 2毒株属于一种在加拿大从未报道过的基因型（命名为PCV - 2b）。对2005年和2006年提交至省级诊断实验室的其他83例加拿大PCV - 2阳性病例进行的进一步序列分析表明，所获得的病毒序列中有79.5%聚集在PCV - 2b基因型中。PCV - 2b基因型在加拿大的出现可能解释了与PMWS相关的死亡率上升，但这种关系有待证实。
