台灣豬瘟之群體免疫狀態

豬瘟 (Classical swine fever)是世界動物衛生組織 (World Organizations for Animal Health)列出之重要疾病。台灣於1938年首次爆發豬瘟疫情，自從1958年乾燥兔化豬瘟疫苗研發成功並常規施打後，豬瘟發生率顯著下降。為因應近年來台灣政府正積極執行豬瘟撲滅計劃，豬瘟免疫適期與免疫成效監控之探討具有其重要性。本研究目的為探討近期台灣豬瘟之群體免疫狀況。研究分成兩部分進行，第一部分試驗為分析仔豬施打疫苗後6至10週之免疫成效 (post immunization efficacy, PIE)；第二部分試驗為了解上市年齡豬隻之免疫保護強度 (finisher pig immunization efficacy, FPE)。血液樣本收集期間為2018年1月至2021年12月，各豬場均收集完整之牧場資料。豬瘟特異性抗體選用IDEXX CSFV Ab ELISA診斷試劑套組檢測，並以群體抗體陽性率、抗體力價平均值及抗體力價平均值之變異係數等三項指標進行免疫成效結果評估。之後再以chi-squared test及Fisher’s exact test針對年度、牧場分佈區域、牧場飼養規模、豬瘟疫苗廠牌和免疫計劃等因素進行分析。第一部分試驗共收集136場，1,188個血液樣本，免疫成效良好的牧場數為90場 (66.2%)；而第二部分試驗收集79場，761個血液樣本，其中33場 (41.8%)為免疫成效良好。第一部分試驗顯示不同年度、豬瘟疫苗廠牌間、母豬每空胎補強疫苗，其仔豬於不同時間施打一劑疫苗及母豬產前補強疫苗，其仔豬於不同時間施打一劑疫苗之免疫成效，組別間均無顯著差異 (P > 0.05)；中北部牧場免疫成效良好率顯著高於南部牧場 (P < 0.05)；飼養1,000-1,999母豬頭數之牧場免疫成效良好率顯著高於飼養201-499母豬頭數之牧場 (P < 0.05)，除外，飼養500-999及1,000-1,999母豬頭數之牧場免疫成效良好率顯著高於飼養 ≥2,000母豬頭數之牧場 (P < 0.05)；免疫計劃的部分，母豬每空胎補強疫苗，其仔豬於4-5週齡施打第一劑疫苗和7-9週齡補強第二劑疫苗組別之免疫成效良好率顯著高於0-1日齡施打第一劑疫苗和4-6週齡補強第二劑疫苗組別，以及3週齡施打第一劑疫苗和6-8週齡補強第二劑疫苗組別 (P < 0.05)。第二部分試驗在不同年度、牧場分佈區域、牧場飼養規模、免疫計劃之免疫成效並無顯著差異 (P > 0.05)；然而豬瘟疫苗廠牌間有統計上之顯著差異 (P < 0.05)。綜上所述，本研究顯示母豬產前補強次單位疫苗，其仔豬於9-12週齡施打一劑疫苗和母豬每空胎補強減毒活毒疫苗，其仔豬於5-8週齡施打一劑疫苗為較適合之免疫適期。最後，台灣部分豬群之豬瘟疫苗免疫成效仍有持續改善之空間。

關鍵字

豬瘟；豬瘟免疫成效；豬瘟群體免疫狀態

並列摘要

Classical swine fever (CSF) has been identified as a crucial disease by the World Organizations for Animal Health. The first outbreak of CSF in Taiwan was in 1938. With the routine application of the lapinized Chinese C-strain vaccine since 1958, the prevalence of CSF has decreased considerably. With the implementation of the Taiwanese government’s CSF eradication program, monitoring the effectiveness of immunization and discussion of appropriate CSF vaccination program are crucial. For these reasons, this study investigated CSF immunity in Taiwan in two parts. The first part was analyzing post immunization efficacy (PIE) after 6 to 10 weeks; the second part was evaluating the immune efficacy of finisher pigs (FPE). Blood samples with complete farm information were collected from January 2018 to December 2021. Samples were tested using an IDEXX CSFV Ab ELISA kit and evaluated in terms of the herd antibody positive rate, mean blocking value of ELISA, and coefficient value of the mean blocking value of ELISA. The data were analyzed through a chi-squared test and Fisher’s exact test on the basis of year, farm location, herd size, CSF vaccine brand, and vaccination program. A total of 1,188 serum samples were collected from 136 PIE herds; 90 herds (66.2%) exhibited satisfactory immune efficacy. A total of 761 serum samples from 79 FPE herds were analyzed; 33 (41.8%) exhibited satisfactory immune efficacy. Factors including year of collection, vaccine brand, sows being vaccinated while not pregnant and piglets receiving one shot of the vaccine, sows being vaccinated during the pre-farrowing stage and piglets receiving one shot of the vaccine did not statistically significantly differ in terms of PIE (P > 0.05). However, the herds from northern and central Taiwan exhibited an immune efficacy that was significantly higher than that of the herds from the south (P < 0.05). The rate of satisfactory immune efficacy in herds of 1,000-1,999 sows was significantly higher than that in herds of 201-499 sows (P < 0.05). The rates of satisfactory immune efficacy in herds of 500-999 and 1,000-1,999 sows were significantly higher than that in herds of ≥2,000 sows (P < 0.05). When sows were vaccinated while not pregnant, piglets vaccinated at 4-5 and 7-9 weeks of age exhibited satisfactory immune efficacy that was significantly higher than that in herds for which piglets were vaccinated at 0-1 day, 4-6 weeks of age and 3, 6-8 weeks of age (P < 0.05). For the FPE, year of collection, farm location, herd size, and vaccination program did not create significant differences (P > 0.05), whereas vaccine brand created significant differences. This study showed appropriate vaccination program are as follows: 1) Swine herds vaccinate sows at the pre-farrowing stage, most likely with CSF-E2 subunit vaccine, and vaccinate piglets at 9 to 12 weeks old; 2) Swine herds vaccinate sows during non-pregnant stage, most commonly with live attenuated vaccines, and vaccinate piglets at 5 to 8 weeks old. The unsatisfactory herd immunity to CSF in Taiwan highlights room for improvement.

並列關鍵字

Classical swine fever ； Classical swine fever immune efficacy ； Classical swine fever herd immunity status ； IDEXX CSFV Ab ELISA

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