篇名:
台灣豬第二型環狀病毒之特徵Characterization of Porcine Circovirus Type 2 in Taiwan
作者:
王?;黃天祥;黃金城;涂堅;鍾明華;林士鈺;賴秀穗
中文摘要:
為了解台灣地區豬第二型環狀病毒基因體變異及流行率,我們進行豬第二型環狀病毒基因體全長定序及收集2000年至2002年之間豬隻血清進行檢測。總計收集623個出現各種臨床症狀之檢體並已聚合?鏈反應進行檢測,結果有309個檢體呈現陽性反應(49.6%)。比較台灣所分離的8株豬第二型環狀病毒分離株基因體,可發現有95%至99%核酸序列相似性。將台灣與世界各國40株豬第二型環狀病毒進行演化樹分析,可發現所有豬第二型環狀病毒被歸類為一大族群,其中包括2較小之亞群,台灣分離株被分為主要2個亞群。由全國各養豬場收集不同豬齡的豬隻血清進行檢測,PCV2陽性率為83.5%。其中肉豬具有高抗體力價,而9週齡之仔豬抗體力價最低。豬第二型環狀病毒感染在台灣養豬豬場已十分普遍。
英文摘要:
In a effort to understand the genetic diversity of porcine circovirus type 2 (PCV2) and the prevalence of PCV2 infection in Taiwanese herds, we have sequenced the complete genomes from PCV2-infected specimens and individually measured the antibody titer against PCV2 from pigs reared in Taiwan between the years 2000 and 2002. A total of 623 specimens originating from pigs displaying varied clinical signs were screened with the polymerase chain reaction (PCR). Results showed that 309 pigs (49.6%) tested positive for PCV2. Eight of the positive specimens were used for the amplification of the complete viral genome. Sequence comparison of the complete genomes indicated that the 8 Taiwanese PCV2 isolates shared 95-99% similarity. Phylogenetic analysis of all 40 PCV2 isolates from North America, Europe, Asia and Taiwan revealed that those isolates were grouped together in one large group containing two minor subgroups. The Taiwanese PCV2 isolates were classified into the two minor subgroups. The prevalence of serum antibodies to PCV2 in pigs was investigated, and results showed that approximately 83.5% of the pigs in Taiwan were seropositive. Finishing pigs possess the highest titers of antibodies, while 9-week-old pigs contained the lowest titers for specific antibodies. Our results suggest that PCV2 infections have become common in Taiwanese pig farms.
備註:
年份:西元 2003 年
期別:第 39 期
詳細內容:
Porcine circovirus (PCV) is non-enveloped virus with a size of 17 nm and contains a single-stranded circular DNA genome [9, 21]. PCV was classified as a member of Circoviridae family [3]. The other six animal members in Circoviridae are chicken anemia virus [21], psittacine beak-and-feather disease virus [21], human transfusion-transmitted virus [18], goose circovirus [30], pigeon circovirus [30] and canary circovirus [22]. Porcine circovirus type 1 (PCV1) and type 2 (PCV2) have two major open reading frames (ORF1 and ORF2). ORF1 is believed to code for the replication-associated protein [16], while ORF2 encodes a major structural capsid protein [20]. Sequence differences between PCV1 and PCV2 are mainly located in ORF2 [5, 9, 16]. PCV2 can be distinguished from PCV1 on the basis of genome sequence and antigenicity [2, 5, 9, 14].  PCV1 has been isolated from a contaminant in the PK-15 cell line [6]. This virus is not considered to be pathogenic to pigs [3, 29]. PCV2 infection has been strongly correlated as the causative agent of postweaning multisystemic wasting syndrome (PMWS), porcine dermatitis nephropathy syndrome (PDNS), congenital tremors, and reproductive failure in pigs [2, 8, 17, 25]. PMWS was first reported in western Canada [7]. PMWS is now known to occur in pig farms in Europe, North America and Asia [2, 11, 19, 26]. However, PCV2 has been identified in pigs even when typical clinical and histological lesions were absent [12]. Serological surveys employing indirect immunofluorescence assays (IFA), indirect immunoperoxidase monolayer assays (IPMA) and enzyme linked immunosorbent assays (ELISA) revealed that antibodies to PCV1 were common in North American and European swine populations [6, 28, 29]. Other studies have shown that cross-reaction exists between PCV1 and PCV2 [13, 14, 23], and that PVC2 appears to be the main PCV type circulating amongst pig populations [13].  PMWS has been reported in Taiwaese pigs [4]. The affected pigs display weight loss, dyspnea and jaundice. Gross lesions include lymphadenopathy, interstitial pneumonia, interstitial hepatitis and nephritis. Histopathological lesions include macrophage infiltration, depletion of lymphoid cells, variable numbers of syncytial cell formation in the lymphoid tissues, and characteristic basophilic intracytoplasmic inclusions are present in macrophage cells. The purpose of this study was to detect PCV2 in various clinical cases using polymerase chain reaction (PCR) assays, compare the complete genomes of Taiwanese PCV2 isolates and realize the seroprevalence of antibodies to PCV2 in pig populations.
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附件名稱:
台灣豬第二型環狀病毒之特徵
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