|摘要: ||豬環狀病毒相關症(Porcine circovirus-associated disease, PCVAD)由豬第二型環狀病毒(Porcine circovirus type 2, PCV2)誘發的多因子疾病，與PCVAD風險因子誘起豬隻亞臨床感染症狀。PCVAD的病徵主為造成消瘦、離乳後死亡率增加，以及使8~16週齡間豬隻混合其他病原之感染率上升，而使養豬產業嚴重經濟損失。除環境管理改善外，國外普遍使用商用PCV2疫苗控制PCVAD，皆呈現良好的效益。然而，台灣養豬型態及潛在疾病流行狀態與國外有所不同，對於台灣使用商用疫苗進行關注評估。首先評估使用PCV2 ORF2次單位疫苗(IngelvacR CircoFLEX™) 控制PCVAD之效益，此試驗於台灣中部一場有PCVAD病史之牧場進行田間試驗。實驗選用連續批次的豬隻(對照1組、免疫組、對照2組)進行試驗，免疫組於21日齡肌肉注射PCV2疫苗。於保育結束時及上市肉豬時期統計消瘦率、死亡率以及肉豬體重，採集試驗豬隻8及12週齡血液進行病毒載量檢測。結果顯示免疫組豬隻於保育及肥育階段分別降低10.4%及7.0%之死亡/消瘦率，在平均上市體重(平均200日齡)中免疫組相較未免疫組可增加8.07公斤體重。然而，與未免疫豬隻相較，PCV2免疫組群在12週齡有較低病毒血症(55%比100%)及病毒載量 (3.16± 3.03比7.38±1.04 log10)，此外，在試驗牧場放線桿菌胸膜肺炎之盛行率降低。由問卷及橫斷面病毒血症監控長時間PCV2免疫牧場，顯示長期使用PCV2疫苗後皆無高病毒載量發生。試驗二主軸比較兩個商用PCV2病毒疫苗(IngelvacR CircoFLEX™和SuvaxynR PCV2)對豬群發生PCVAD之效益。此試驗在另一牧場進行，選用連續3批次仔豬進行分組(Ingelvac組、對照組、Suvaxyn組)及疫苗免疫，結果顯示二疫苗免疫組相對於對照組在肉豬前期階段，皆能有效降低8.7%之死亡/消瘦率及降低病毒載量。在肥育前期的PCV2病毒血症及降低死亡/消瘦率方面，兩個疫苗間並無差異性。綜上所述，台灣新上市兩種PCV2疫苗可以有效控制PCVAD及提升肥育豬生長性能，然而環境及管理因素仍會明顯影響PCV2疫苗控制PCVAD效益。|
Porcine circovirus-associated disease (PCVAD) is a multifactor disease caused by porcine circovirus type 2 (PCV2) sub-clinically infected pigs triggered with PCVAD risk factors. PCVAD is characterized by weight loss, increasing post-weaning mortality and co-infection with other pathogens between 8~16 weeks of age and causes serious economic loss in pig industry. Besides improvement of management, several commercial PCV2 vaccines have been used in controlling PCVAD and displayed good protective efficacy in PCVAD control. However, the types of swine production and disease endemic in Taiwan are different from other countries. The efficacies of those vaccines used in Taiwan are particularly concerned. The first field trial was to evaluate the PCV2 ORF subunit vaccines (IngelvacR CircoFLEX™) in PCVAD Control 1n a farm with PCVAD history. Three consequent batches of experimental pigs (Control 1, Vaccination, and Control 2 groups) were used in the study, in which piglets in vaccination group were intramuscularly vaccinated with PCV2 vaccine once (1 mL) at 21 days of age. The percentage of the pigs with wasting syndrome, mortality, and the body weight were evaluated at the end of nursery stage and market day. The PCV2 viral loads in blood of experimental pigs at 8 and 12 weeks of age were tested by quantitative PCR. The results displayed that there were 10.4% and 7.0% decreases in dead/wasting pigs during the nursery and finishing periods of vaccinated pigs, respectively, compared to controls. The mean body weight at market (200 days of age) in the immunized group was 8.07 kg heavier than those of the non-vaccinated controls. Moreover, compared with non-immune pigs, PCV2 vaccination pigs at 12 weeks of age showed lower viremia rate (55% versus 100%) and less virus loads (3.16� 3.03 versus 7.38�1.04). Besides, the prevalence of Actinobacillus pleuropneumoniae in the experimental farms was also obviously reduced. The questionnaire and cross-sectional monitoring of viremia in PCV2 vaccinational farms showed there was no high viral load in vaccination pigs after long-term PCV2 vaccination. The aim of trial 2 was to compare the efficacy of two commercial PCV2 vaccines (IngelvacR CircoFLEX™ and SuvaxynR PCV2) in PCVAD control. The experiment was conducted in the second farm using 3 consequent batches of piglets (Group Ingelvac, control group, and group Suvaxyn). The results showed that both vaccination groups displayed 8.7% decrease in death/wasting rates and viral loads during pre-finishing periods were also descreased, compared to the non-immune pigs. There were no differences in PCV2 viral loads and the reduction of death/wasting rate in pre-finishing stage of experimental pigs in both vaccines. Taken together, both PCV2 vaccines newly launched in Taiwan can efficiently control PCVAD and improve finishing performance. However the efficacy of PCV2 vaccine in PCVAD Control 1s also significantly influenced by the quality of environmental and management factors of farms.