译者的话：<<

研究表明，ASFV、CSFV和PRV在跨洋运输环境条件下都能在饲料原料中存活。3种外来动物疫病病毒均能在一般的豆粕和猪肉香肠肠衣中存活。ASFV在猪群自然摄入被污染的液体和饲料后，可通过口路传播，通过植物性饲料感染需要更高的剂量。病毒衰减试验证明，所有饲料原料中ASFV的稳定性均高于培养基中的稳定性，所有饲料原料中ASFV的平均半衰期估计为12.2天。综上所述，这些研究为饲料在猪外来疫病跨国传播中的潜在作用提供了证据。

介绍Introduction<<

作者 Author:

M. C. Niederwerder, DVM, PhD 兽医，博士

美国堪萨斯州，堪萨斯州立大学，兽医学院，诊断医学/病理学系

Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas

引言 Introduction

自从2013年猪流行性腹泻病毒（PEDV）在美国爆发以来，饲料和饲料原料一直被认为有跨国界传播生猪疫病的风险。在外来动物疫病疫源国进行饲料原料生产后，由于市场的全球分布和出口活动，使得饲料具有在非疫源国引入和传播疫病的风险。在美国和世界其他国家，非洲猪瘟病毒（ASFV）、经典猪瘟病毒（CSFV）、变异株伪狂犬病毒（PRV）是三种最严重的猪生产疫病威胁。本研究的目的就是调查饲料和饲料原料引入和传播非洲猪瘟病毒（ASFV）、经典猪瘟病毒（CSFV）、变异株伪狂犬病毒（PRV）的风险。本研究目的通过三个试验方法达成：1）模拟横跨大洋运输的各类环境条件，检测外来动物疫病在该种条件下于饲料和饲料原料中的存活情况；2）调查外来动物疫病通过自然摄入被污染饲料而传播的可能性以及所需的饲料摄入量；3）减少饲料和饲料原料中外来动物疫病传播风险的评估工具。

Since the incursion of porcine epidemic diarrhea virus (PEDV) into the United States in 2013, feed and feed ingredients have been recognized as a risk for transboundary spread of swine diseases. The global distribution and export market for ingredients manufactured in countries with circulating foreign animal diseases (FAD) make feed a risk for disease introduction and transmission into naïve countries. African swine fever virus (ASFV), classical swine fever virus (CSFV) and variant pseudorabies virus (PRV) are three of the most significant threats to pork production in the US and around the world. The objective of this research was to investigate feed and feed ingredients as a risk for ASFV, CSFV, and PRV introduction and transmission. This objective was targeted with a three part approach, including 1) determining the survival of FAD in feed and feed ingredients subjected to varying environmental conditions simulating trans-oceanic shipment, 2) investigating the probability and dose necessary for FAD transmission through the natural consumption of contaminated feed, and 3) assessing tools for mitigating the risk of FAD transmission in feed and feed ingredients.

材料与方法 Materials and methods<<

所有猪群和病毒相关操作均在位于堪萨斯州立大学校区内部的生物安全3级实验室，即生物安全研究所进行。为了检测外源动物疫病病毒在进口饲料原料中的稳定性，研究使用了环境舱以模拟越洋运输情况下的温度变化和湿度条件。试验探究了12种饲料或饲料原料中非洲猪瘟病毒（格鲁吉亚2007毒株，Georgia 2007）、经典猪瘟病毒（布雷西亚毒株，Brescia）以及变异型伪狂犬病毒（HeN1 株）在30-37天跨洋运输条件下的稳定性。病毒稳定性通过定量PCR、病毒分离和滴度测定以及生猪活体鉴定来确定。采用保育猪自然采食少量被特定剂量非洲猪瘟病毒污染的液体或饲料的方法，鉴定非洲猪瘟病毒通过饲料的传播特性。所饲喂的非洲猪瘟病毒滴度区间为 10⁰TCID50到10⁸ TCID50，猪群通过重力给水的水嘴自然采食液体、通过不锈钢料槽自然采食饲料。5天之后，通过多种检测方法确认了非洲猪瘟感染。通过30天的越洋运输模型实验，鉴定发现非洲猪瘟病毒在9种饲料原料中会出现病毒衰变；基于适中的温度和湿度条件，研究预测了非洲猪瘟病毒的半衰期（附带标准误（SE）和置信区间（CI））。在污染后1、8、17和30天进行了病毒滴度测定。

All work with pigs and viruses was performed at the Biosecurity Research Institute, a biosafety level 3 laboratory housed on the Kansas State University campus. To investigate stability of FAD through imported feed ingredients, an environmental chamber was used to simulate fluctuating temperature and humidity conditions in transoceanic shipment models. Stability of ASFV Georgia 2007, CSFV Brescia strain, and variant PRV HeN1 were investigated in 12 feeds or feed ingredients in 30-37 day trans-oceanic models. Viral stability was determined through quantitative PCR, virus isolation and titration, and swine bioassays. Transmission of ASFV through feed was investigated in nursery pigs through the natural consumption of small volumes of liquid and feed contaminated with specific doses of ASFV. Doses administered ranged between 100 TCID50 and 108 TCID50. Pigs naturally consumed liquid in gravity-fed drinkers and naturally consumed feed in stainless steel creep feeders. ASFV infection was detected after 5 days using multiple diagnostic assays. Viral decay of ASFV was characterized in 9 feed ingredients over the course of a 30-day transoceanic shipment model to estimate viral half-life with SE and CI at moderate temperature and humid-ity conditions. Viral titrations were performed at 1, 8, 17 and 30 days post-contamination. 

结果和讨论 Results and discussion<<

ASFV、CSFV和PRV在跨洋运输环境条件下都能在饲料原料中存活；与ASFV和PRV相比，CSFV能存活的饲料原料种类较少。3种外来动物疫病病毒均能在一般的豆粕和猪肉香肠肠衣中存活。ASFV在猪群自然摄入被污染的液体和饲料后，可通过口路传播，通过植物性饲料感染需要更高的剂量。病毒衰减试验证明，所有饲料原料中ASFV的稳定性均高于培养基中的稳定性，所有饲料原料中ASFV的平均半衰期估计为12.2天。综上所述，这些研究为饲料在猪外来疫病跨国传播中的潜在作用提供了证据。

ASFV, CSFV and PRV were all capable of surviving in feed ingredients subjected to transoceanic environmental conditions, with CSFV surviving in fewer ingredients compared to ASFV and PRV. All 3 foreign animal diseases survived in conventional soybean meal and pork sausage casings. ASFV was transmissible through the oral route after the natural consumption of contaminated liquid and feed, with higher doses required for infection through plant-based feed. Stability of ASFV was increased in all feed ingredients when compared to viral decay in media, with the average half-life of ASFV in all feed ingredients estimated at 12.2 days. Taken together, these studies provide evidence for the potential role of feed in the transboundary spread of foreign ani-mal diseases of swine.

参考文献 References<<

1. Dee, S. A., F. V. Bauermann, M. C. Niederwerder, A. Singrey, T. Clement, M. de Lima, C. Long, G. Patterson, M. A. Sheahan, A. M. M. Stoian, V. Petrovan, C. K. Jones, J. De Jong, J. Ji, G. D. Spronk, L. Minion, J. Christopher-Hennings, J. J. Zim-merman, R. R. R. Rowland, E. Nelson, P. Sundberg and D. G. Diel. Survival of viral pathogens in animal feed ingredients under transboundary shipping models. PLoS One 2018;13(3): e0194509.

2. Niederwerder, M. C., A. M. M. Stoian, R. R. R. Rowland, S. S. Dritz, V. Petrovan, L. A. Constance, J. T. Gebhardt, M. Olcha, C. K. Jones, J. C. Woodworth, Y. Fang, J. Liang and T. J. Hefley. Infectious Dose of African Swine Fever Virus When Consumed Naturally in Liquid or Feed. Emerg Infect Dis 2019;25(5): 891-897.

3. Stoian, A. M. M., J. Zimmerman, J. Ji, T. J. Hefley, S. Dee, D. G. Diel, R. R. R. Rowland and M. C. Niederwerder. Half-Life of African Swine Fever Virus in Shipped Feed. Emerg Infect Dis 2019;25(12): 2261-2263.

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