Evaluation of the minimum infectious dose of porcine epidemic diarrhea virus in virus-inoculated feed
Evaluation of the minimum infectious dose of porcine epidemic diarrhea virus in virus-inoculated feed
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DOI：
10.2460/ajvr.77.10.1108
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发表时间：
2016-10-01
影响因子：
1
通讯作者：
Dritz, Steve S.
中科院分区：
文献类型：
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作者：
Schumacher, Loni L.;Woodworth, Jason C.;Dritz, Steve S.
目的研究猪流行性腹泻病毒（PEDV）在猪饲料中的最小感染量。方法将猪流行性腹泻病毒（PEDV）的组织培养物稀释成8个10倍的系列稀释液。将一等份储备病毒（5.6 × 10（5）TCID 50/mL）和每个系列PEDV稀释液混合到4.5-kg批次的饲料中，以产生9个PEDV接种的饲料剂量;还产生1个病毒阴性剂量的饲料中的培养基。通过经口给予PEDV接种饲料对猪进行攻毒暴露，并采集粪便拭子样本。所有猪在攻击暴露后7天被安乐死;收集新鲜组织并用于PCR测定、组织学检查和免疫组织化学分析。与在组织培养基中稀释的等效PEDV的结果相比，当将PEDV加入饲料中时，PCR循环阈值（Ct）降低约10。当用4种最高浓度（引起感染的最低浓度，5.6 × 10（1）TCID 50/g;组织培养基中的Ct = 27，饲料中的Ct = 37）进行攻击时，猪被PEDV感染。饲料中最低感染性PEDV剂量的Ct为37，这可能高于一些诊断实验室使用的PEDV PCR测定法所建立的检测限。总体而言，结果表明5.6 X 10（1）TCID 50/g是在本研究条件下可导致10日龄猪感染的饲料中的最小PEDV剂量。
OBJECTIVETo determine the minimum infectious dose of porcine epidemic diarrhea virus (PEDV) in virus-inoculated feed.ANIMALS30 crossbred 10-day-old pigs.PROCEDURESTissue culture PEDV was diluted to form 8 serial 10-fold dilutions. An ali-quot of stock virus (5.6 X 10(5) TCID50/mL) and each serial PEDV dilution were mixed into 4.5-kg batches of feed to create 9 PEDV-inoculated feed doses; 1 virus-negative dose of culture medium in feed was also created. Pigs were challenge exposed via oral administration of PEDV-inoculated feed, and fecal swab specimens were collected. All pigs were euthanized 7 days after challenge exposure; fresh tissues were collected and used for PCR assay, histologic examination, and immunohistochemical analysis.RESULTSThe PCR cycle threshold (Ct) decreased by approximately 10 when PEDV was added to feed, compared with results for equivalent PEDV diluted in tissue culture medium. Pigs became infected with PEDV when challenge exposed with the 4 highest concentrations (lowest concentration to cause infection, 5.6 X 10(1) TCID50/g; Ct = 27 in tissue culture medium and 37 in feed).CONCLUSIONS AND CLINICAL RELEVANCEIn this study, PEDV in feed with detectable Ct values of 27 to 37 was infective. The Ct was 37 for the lowest infective PEDV dose in feed, which may be above the limit of detection established for PEDV PCR assays used by some diagnostic laboratories. Overall, results indicated 5.6 X 10(1) TCID50/g was the minimum PEDV dose in feed that can lead to infection in 10-day-old pigs under the conditions of this study.