台灣地區豬第三型環狀病毒於豬群橫斷面之病毒分佈、基因特性及與豬第二型環狀病毒之相關性分析

豬環狀病毒 (Porcine circovirus) 於豬隻產業具有重要之影響，而豬第三型環狀病毒 (Porcine circovirus type 3; PCV3) 為近年來新發現之環狀病毒。先前研究發現PCV3和豬呼吸道疾病綜合症 (Porcine respiratory disease complex; PRDC) 有關，對於保育豬及肥育豬極具重大影響。關於PCV3於呼吸道症狀及病毒動態分布之影響許多國家已有研究，但台灣卻少有PCV3之相關研究。為了解台灣地區PCV3於不同週齡豬群之病毒動力學、及具呼吸道症狀之保育豬及肥育豬之PCV3檢出率及與鄰近國家PCV3之基因親緣關係，本研究蒐集送檢至國立屏東科技大學動物疾病診斷中心之母豬與不同週齡肉豬之血清，另蒐集具呼吸道症狀保育豬及肥育豬之血清，使用即時定量聚合酶連鎖反應檢測PCV3。選擇PCV3高病毒血症之陽性檢體進行PCV3全長基因序列分析，並參考2017年至2020年國外發表之PCV3病毒株序列進行交叉比對；為確定蒐集之檢體為PCV3感染所造成之病變，本研究另選擇PCV3陽性病例之肺臟與肺門淋巴結進行PCV3 in-situ hybridization染色。橫斷面調查結果顯示母豬PCV3之檢出率 (45/90; 50%) 顯著高於4週齡以下豬隻 (9/100; 9%)、4-12週齡豬隻 (25/260; 9.6%) 及12週齡以上豬隻 (77/460; 16.7%) 之檢出率 (p<0.05)；而母豬及各週齡豬隻PCV3病毒量為0-10^5.46 copies/μL。具呼吸道症狀豬隻之PCV3檢出率及病毒量於保育豬及肥育豬則無顯著差異 (p>0.05)，但PCV3陽性病例常見豬生殖與呼吸綜合症病毒 (Porcine reproductive and respiratory syndrome virus; PRRSV) 或豬第二型環狀病毒 (Porcine circovirus type 2; PCV2) 之混合感染；原位雜合染色結果顯示於肺門淋巴結組織中呈現PCV3陽性訊號。序列分析後顯示台灣PCV3病毒株與國內外病毒株其全長序列之核苷酸相似度為98.4-99.8%，而ORF2全長序列之核苷酸相似度為98.0-99.9%。PCV3於台灣豬場普遍可見且全年齡豬隻皆可感染，其中以母豬檢出率為最高。而台灣PCV3病毒株與國內外文獻PCV3病毒序列極為相似。PCV3對於台灣豬隻呼吸道疾病中檢驗比例較少但混合感染PRRSV或PCV2之情況常見。

關鍵字

豬第三型環狀病毒；豬第二型環狀病毒；豬呼吸道疾病綜合症；豬；台灣

並列摘要

Porcine circovirus has an important influence in the swine industry. Porcine circovirus type 3 (PCV3) is a newly emerging circovirus. In previous studies, PCV3 is related to porcine respiratory disease complex (PRDC). PRDC has great impacts on nursery and growing pigs. The impact of PCV3 in respiratory symptoms and the dynamic of viremia profiles of PCV3 had been reported in many countries, but there is limited relevant research of PCV3 in Taiwan. The purpose of this study is to understand the detection rate of PCV3 in cross-sectional pigs, and to understand PCV3 detective rate of nursery and growing pigs with respiratory symptoms and the phylogenetic relationship in Taiwan compared with different PCV3 isolates in neighbor countries. The serum samples from 3 to 31 weeks old and sows, and the serum samples from nursery and growing pigs with respiratory signs were collected in Animal Disease Diagnostic Center of National Pingtung University of Science and Technology. All serum samples were screened for PCV3 by real-time PCR. The whole genome sequences of high viral load samples were analyzed and compared with different PCV3 isolates in different countries. To confirm the samples infected by PCV3, the lungs and hilar lymph nodes from PCV3 positive cases were performed in-situ hybridization. The results of cross-sectional pigs showed PCV3 detection rate was significantly (p<0.05) higher of sow (45/70; 50%) than in pigs below 4 weeks old (9/100; 9%), pigs with 4-12 weeks old (25/260; 9.6%) and pigs over 12 weeks old (77/460; 16.7%). PCV3 viral loads ranged from 0-10^5.46 copies/μL in sow and different aged pigs. No significant differences of PCV3 detectione rate and viral load were observed among the cases with respiratory signs in nursery and growing pigs. However, most PCV3 positive cases were co-infected with porcine reproductive and respiratory syndrome virus or porcine circovirus type 2. PCV3 positive signals could be observed in hilar lymph nodes with in situ hybridization. Taiwanese PCV3 strains share 98.4-99.8% and 98.0-99.9% nucleotide identity in the complete genome and ORF2, respectively, compared with reference PCV3 strains. PCV3 is widely spread and can infect all aged pigs in Taiwan. Phylogenetic analysis of two PCV3 strains shows a high nucleotide identity with the reference PCV3 strains. PCV3 has less detection rate on respiratory disease in Taiwan but coinfection with PRRSV or PCV2 is common in pig herds.

並列關鍵字

Porcine circovirus type 3 ； Porcine circovirus type 2 ； porcine respiratory disease complex ； pig ； Taiwan

參考文獻

邱明堂、蘇保誠、莊孟修、林昭男 (2004) 台灣地區罹病豬隻中第二型豬環狀病毒感染狀況之調查。台灣獸醫學雜誌。30: 163-168

Google Scholar

曾家筠 (2018) 臺灣地區第三型豬環狀病毒之調查及序列分析。國立屏東科技大學碩士論文。

Google Scholar

Afghah, Z., Webb, B., Meng, X. J., and Ramamoorthy, S. (2017). Ten years of PCV2 vaccines and vaccination: is eradication a possibility? Vet Microbiol 206: 21-28.

Google Scholar

Arruda, B., Pineyro, P., Derscheid, R., Hause, B., Byers, E., Dion, K., Long, D., Sievers, C., Tangen, J., Williams, T., and Schwartz, K. (2019). PCV3-associated disease in the United States swine herd. Emerg Microbes Infect 8: 684-698.

Google Scholar

Bera, B. C., Choudhary, M., Anand, T., Virmani, N., Sundaram, K., Choudhary, B., and Tripathi, B. N. (2020). Detection and genetic characterization of porcine circovirus 3 (PCV3) in pigs in India. Transbound Emerg Dis 67: 1062-1067.

Google Scholar

主題瀏覽