National Veterinary Institute, The Technical University of Denmark, DK-1790 Copenhagen V, Denmark.
Vet Microbiol. 2009 Nov 18;139(3-4):219-26. doi: 10.1016/j.vetmic.2009.06.001. Epub 2009 Jun 11.
Post-weaning Multisystemic Wasting Syndrome (PMWS) has been identified in most swine-producing countries worldwide. The disease has resulted in significant health challenges and economic damage to the swine industry. The aim of this study was to determine horizontal transmission of porcine circovirus type 2 (PCV2) and to examine viral dynamics in pigs in a controlled PMWS transmission study. In the study pigs from PMWS-affected herds and non-affected herds were permitted to have close contact (same pen), nose-to-nose contact (to pigs in neighbouring pens) or no physical contact (pen across the aisle and pens in other compartments). By DNA sequence analysis, eight variants of genotype PCV-2b were identified in the research facility. From the spread of these PCV2-variants it was concluded that PCV2 primarily infects through close contact and nose-to-nose contact. PCV2 genome sequences were obtained from selected pigs at arrival to the research facility and again when the same pigs developed PMWS. This analysis showed that pigs from PMWS-affected herds developed PMWS caused by the same variant of PCV2 as they carried when entering the research facility. In contrast, pigs from non-affected herds developed PMWS with PCV2-variants identified in pigs from PMWS-affected herds. This was probably connected to at least 10(3) higher mean serum-titer of PCV2 in pigs from PMWS-affected herds as compared to pigs from non-affected herds at the beginning of the transmission study. The study further showed that pigs able to control the PCV2 infection, as measured by the PCV2-titer in serum, recovered clinically (pigs from PMWS-affected herds) or stayed healthy (pigs from non-affected herds). Like this, pigs with a PCV2 titer below 5x10(8) copies/ml serum during the study period had a chance of recover from the PCV2 infection whereas pigs with PCV2 titers above 5x10(8) copies/ml serum at any time point generally died from PMWS.
断奶后多系统消耗综合征 (PMWS) 已在世界上大多数养猪国家被发现。该疾病给养猪业带来了重大的健康挑战和经济损失。本研究的目的是确定猪圆环病毒 2 型 (PCV2) 的水平传播，并在控制 PMWS 传播研究中检查猪中的病毒动态。在该研究中，来自 PMWS 感染和未感染猪场的猪被允许进行密切接触（同一猪舍）、鼻对鼻接触（相邻猪舍的猪）或无身体接触（过道对面的猪舍和其他隔栏中的猪舍）。通过 DNA 序列分析，在研究设施中鉴定出 8 种基因型 PCV-2b 的变体。从这些 PCV2 变体的传播情况来看，PCV2 主要通过密切接触和鼻对鼻接触进行感染。从选定的猪在进入研究设施时以及在同一猪出现 PMWS 时获得了 PCV2 基因组序列。该分析表明，来自 PMWS 感染猪场的猪发生 PMWS 是由其进入研究设施时携带的相同 PCV2 变体引起的。相比之下，来自未感染猪场的猪发生 PMWS 是由来自 PMWS 感染猪场的猪中鉴定出的 PCV2 变体引起的。这可能与在传播研究开始时，来自 PMWS 感染猪场的猪的血清 PCV2 平均滴度比来自未感染猪场的猪高至少 10（3）倍有关。该研究进一步表明，能够控制 PCV2 感染的猪（通过血清中的 PCV2 滴度来衡量）在临床上恢复（来自 PMWS 感染猪场的猪）或保持健康（来自未感染猪场的猪）。因此，在研究期间血清 PCV2 滴度低于 5x10（8）拷贝/ml 的猪有机会从 PCV2 感染中恢复，而任何时间点血清 PCV2 滴度高于 5x10（8）拷贝/ml 的猪通常会死于 PMWS。
