Department of Clinical Studies, Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Virol J. 2011 Sep 13;8:437. doi: 10.1186/1743-422X-8-437.
Porcine circovirus type 2 is the primary etiological agent associated with a group of complex multi-factorial diseases classified as Porcine Circovirus Associated Diseases (PCVAD). Sporadic cases reported in Malaysia in 2007 caused major economic losses to the 2.2 billion Malaysian ringgit (MYR) (approximately 0.7 billion US dollar) swine industry. The objective of the present study was to determine the association between the presence of PCV2 and occurrences of PCVAD.
This study showed that 37 out of 42 farms sampled were positive for PCV2 using PCR screening. Thirteen whole genome of PCV2 isolates from pigs with typical PCVAD symptoms were successfully sequenced. These isolates shared 98.3-99.2% similarities with sequences of isolates from The Netherlands. All thirteen isolates fell into the same clade as PCV2b isolates from other countries. Amino acid sequence analysis of the putative capsid protein (ORF2) of the PCV2 revealed that there are three clusters found in Malaysia, namely cluster 1C and 1A/1B. Of interest, three of the isolates (isolates Mal 005, Mal 006 and Mal 010) had a proline substitution for arginine or isoleucine encoded at nt. position 88-89. Eight of the isolates had mutations at the C terminus of the putative capsid protein suggestive of higher pathogenicity which may account for the high reports of PCVAD clinical symptoms in 2007.
Phylogenetic study suggests that there may be a link between movements of animals by import of breeders into the country being the route of entry of the virus. While it is not possible to eradicate the virus from commercial pigs, the swine industry in Malaysia can be safeguarded by control measures implemented throughout the country. These measures should include improved biosecurity, disease surveillance; vaccination as well as enforcement of regulations formulated to control and prevent the spread of this disease on a national scale.
猪圆环病毒 2 型是与一类复杂的多因素疾病相关的主要病原，这些疾病被归类为猪圆环病毒相关疾病（PCVAD）。2007 年在马来西亚零星报告的病例给价值 22 亿林吉特（约合 7 亿美元）的生猪产业造成了重大经济损失。本研究的目的是确定 PCV2 的存在与 PCVAD 发生之间的关联。
本研究显示，使用 PCR 筛选，在 42 个采样农场中有 37 个呈 PCV2 阳性。从具有典型 PCVAD 症状的猪中成功分离出 13 株全基因组 PCV2 分离株进行测序。这些分离株与来自荷兰的分离株的相似度为 98.3-99.2%。所有 13 个分离株都与来自其他国家的 PCV2b 分离株属于同一分支。对 PCV2 假定衣壳蛋白（ORF2）的氨基酸序列分析表明，马来西亚存在三个聚类，即聚类 1C 和 1A/1B。有趣的是，其中 3 个分离株（分离株 Mal 005、Mal 006 和 Mal 010）在 nt 位置 88-89 处发生精氨酸或异亮氨酸取代脯氨酸。8 个分离株在假定衣壳蛋白的 C 末端发生突变，提示更高的致病性，这可能是 2007 年 PCVAD 临床症状高报告的原因。
系统发育研究表明，动物的进口（如种猪的引进）可能是病毒传入的途径，这两者之间可能存在联系。虽然不可能从商业猪中根除该病毒，但可以通过在全国范围内实施控制措施来保护马来西亚的养猪业。这些措施应包括加强生物安全、疾病监测、疫苗接种以及执行旨在控制和预防这种疾病在全国范围内传播的法规。
