译者的话：<<

PIC以其严格的生物安全闻名于世，也成为业内生物安全方面学习的典范。本文介绍了传播概率、有效接触率等基本概念，强调并非接触频率越高，疾病传播的风险就一定越大。介绍了生物安全计划实施的四个方面：风险评估、政策和指导方针、教育、基础设施。并谈到了运输生物安全计划包含四个组成部分：风险评估、车辆分开及隔离时间、清洗和消毒流程、装卸猪只流程（三段论）。以上运输生物安全的组成部分看似耗时耗力，增加了成本，但是从保护扩繁场和客户场不发病的角度来讲，这些投资必定物有所值。

介绍Introduction<<

作者 Authors:

Jean Paul Cano, DVM, PhD

A. Pitkin, DVM, MS

D. Hemker, DVM, MS

J. Geiger, DVM, MS

J. Waddell, DVM, MS

M. Clavijo, DVM, PhD

M. Rotolo, DVM, PhD

T. Riek, DVM

以上作者均来自美国田纳西州PIC公司

简介 Introduction

运输在现代养猪生产中不可或缺。在美国，每周运输猪只数量高达500多万头。运送这些猪只的车头、拖车和司机都可能感染传染性病原，如：蓝耳病毒、猪流行腹泻病毒、短螺旋菌属、口蹄疫病毒、非洲猪瘟病毒、塞内卡病毒等。种猪群的运输尤为重要，主要原因有两个：

Transportation is an essential activity in modern pig production. More than five million pigs get transferred every week in the USA. Tractors, trailers and drivers moving those pigs can become contaminated with infectious agents such as PRRSV, PEDV, Brachispira sp, FMDV, ASFV, SVA, etc. Transportation of breed-ing stock is especially critical because two main reasons:

1.         后备母猪和公猪会进入种猪群和公猪站，它们处在整个生产链条的顶端。

Replacement gilts and boars are introduced to breeding herds and boar studs, the top of the production chain.

2.         核心场和扩繁场通常是闭群的，没有猪只引入，且地处养殖密度相对较低的区域。因此，污染的运输车辆会给这些农场带来风险，相对于农场感染的总风险来讲，这个风险占比是极大的。

Genetic nucleuses and multipliers are usually closed for pig introductions and located in lower pig density regions. Therefore, the risk posed by contaminated transport vehicles represents a large component of the total risk of infection for these farms.

传播 Transmission<<

传播概率是指感染源与易感宿主接触，传染性微生物成功地在两者间传播，并引发感染的可能性。感染源和易感个体之间需要有效的接触，用公式表示为：

Transmission probability is the likelihood that the contact be-tween an infective source and a susceptible host successfully transfers the microbe causing an infection. An effective contact between the infectious and the susceptible individuals is required, and it is represented as:

β = γ × ρ

有效接触率（β）是每个时间单位的接触总数（γ）和每次接触中被感染概率（ρ）的函数。因此，农场实际感染风险为多大，是由某个事件发生的频率与每次在事件中病原感染猪只的可能性共同决定的。每次事件如（运输、人员/物料进场、饲喂、清除死亡猪只/粪便等）会将疾病引入猪群，引发感染。例如，在一个母猪场，虽然每周断奶好几次，但如果断奶仔猪装载流程操作合理且持续性好，则疾病传播的可能性就相对较低。而另一方面，虽然淘汰母猪的频率较低，但如果车辆（车头后面拉着拖车）驾驶员去售猪点或屠宰场，则接触病原体的可能性更高，即使清洗消毒和装载猪只的流程和上个例子中类似，病原传播可能性还是会更大。

The effective contact rate (β) is a function of the total number of contacts per time unit (γ) and the probability of infection in every contact (ρ). Therefore, the relationship between the frequency of an event and the likelihood that during that event a pathogen can infect a pig determines the actual risk for a production practice (transport, people/supply entry, feeding, mortality/manure removal, etc) to cause introduction of disease into a herd. For example, in a sow farm, loading weaned pigs happens several times per week but the likelihood of transmission is relatively low if the decontamination and loading process are consistently per-formed appropriately. In the other hand, culled sows are removed less often but if the tractor-trailer-driver contact a collection point or a slaughter facility exposure to pathogens is higher in-creasing the likelihood of transmission even if decontamination and loading procedures are similar. 

疾病传播可以通过传染性宿主和易感宿主之间的直接接触而发生，例如鼻对鼻传播。疾病也可以通过间接接触传播，如：在病原微生物仍具传染力时，生物或机械载体、空气、水、食物、设施、设备或被病原污染的人员与以上载体和易感宿主接触，会传播疾病。与猪流感病毒或支原体等更脆弱的病原体相比，圆环病毒2型或蛔虫等病原体在环境存活更久，感染易感猪的能力更强。通过清洗和消毒干燥，减少了易感猪只与被感染猪只污染的载体之间的接触。

Disease transmission can occur through direct contact between the infectious and the susceptible hosts, e.g. nose-to-nose, or in-direct contact when biological or mechanical vectors, air, water, food, facilities, equipment or people become contaminated by an infectious host and get exposed to a susceptible host while the microorganism is still infective. Agents with the ability to survive longer in the environment such as PCV2 or Ascaris suum are potentially capable of infecting more susceptible pigs than more fragile agents like IAV or mycoplasmas because potential longer contact opportunity. Washing-disinfecting-drying protocols reduce the access of susceptible pigs to objects contaminated by infectious pigs.

风险管理 Risk management<<

生物安全计划旨在确定和减轻传染性病原体传入猪群并传播开来的风险，它的有效实施需要以下四个方面的配合：

A biosecurity program aims to identify and mitigate the risk of introduction and dissemination of infectious agents to a population. The effective implementation of the program requires the integration of four main components:

1.         风险评估：持续不断地、系统地寻找任何可能引入疾病的机会，借此机会对风险进行半量化衡量，稽核常规流程，确定投资优先级并对团队进行培训。

Risk assessment: the continuous and systematic search for any potential opening for disease introduction is an opportunity to semi-quantify risks, audit routine processes, prioritize investments and educate teams.

2.         政策和指导方针：至关重要的是，用于制定并交流的生物安全方案，它的信息和开发工具应基于科学的基础之上、前后一致、实用性好、易于理解，完整性强。

Policy and guidelines: it is critical that the information and tools used to develop and communicate the biosecurity program are science-based, consistent, practical and easy to understand but complete.

3.         教育：要促进团队所有成员的参与度和担当力，需要适当的培训和再培训。已有多个体系在每个农场或每个上下游生产链中都找出了一个团队生物安全的宣传冠军，这样有助于传播信息，保持团队参与度。

Education: to drive engagement and accountability from all members of the organization, opportune and suitable training and retraining is required. Several systems have promoted a local biosecurity champion in each farm or flow to help dissemination of the information and keeping team engagement.

4.         基础设施：养猪生产中需使用的所有设施设备（拖车、转猪通道），或可以减轻某些风险因素（空气过滤器，加热干燥系统）的设施设备，它们虽然是一项投资，但在疾病预防中起着重要作用。如果没有适当地实施上面的三点，基础设施就成为了巨额的成本，而没有或只有很少的投资回报。

Infrastructure: all equipment and facilities that need to be used in pork production (trailers, loading chutes) or that can help to mitigate certain risk factors (air filters, TADD systems) represent an investment but play a significant role in disease prevention. Without the appropriate implementation of the three previous components, infrastructure becomes a heavy cost with no or little return on the investment.

运输生物安全的组成部分

Components of transportation biosecurity<<

PIC北美运输部门每年协调大约2100家种猪场的运输工作。在过去的27年中，只有两次是因为运输引起的发病。这向客户猪场保证了运输的生物安全，且良好的记录持续不变。这个运输生物安全计划包含四个组成部分：

PIC North American transport coordinates approximately 2,100 breeding stock shipments per year. In the last 27 years, only two disease breaks were attributed to transportation. This establishes a consistent record of biosecure transport to customer herds. This program consists of four components:

1.   风险评估Risk assessments:

a)         运输消毒设施评估工作是对所有与PIC相关的卡车清洗和消毒点做出稽核。该稽核工作会评估设施条件、非PIC清洗和消毒的车辆数量、人员生物安全培训和清洗流程（水温、压力、消毒剂类型、清洗剂的使用和干燥）。

Transportation decontamination facility assessment is used to audit all PIC associated truck wash and drying locations. This audit evaluates facility conditions, number of non-PIC washes, personnel biosecurity training, and wash procedures (water temperature, pressure, disinfectant class, detergent use, and drying).

b)        运输评估列示出每个清洗和消毒中心的运输事件及相关生物安全。它按照类别（拖车、车头、司机）评估每月运输事件的频率和细节。

Transportation assessment maps transportation events and associated biosecurity by site. It evaluates the frequency and details of transport events per month, by category of movement, for the trailer, tractor and driver.

2.   车辆分开及隔离时间：有文献记载了猪流行性腹泻病毒及最近的塞内卡病毒A型，它们会造成拍卖点和屠宰场的严重污染，这是由以上地点的功能本身决定的。车头、拖车和驾驶员在售猪点和屠宰场受到污染的可能性在上升，因此，他们在商品场和种猪场的运输之间不能存在交叉，要分开来。如果少数情况下不能分开时，则在清洗和消毒后隔离时间要延长到72小时。猪只从一辆卡车转移到另外一辆，拉猪车车头卸掉拖车后，连接另一辆拖车，这都是可以分开车辆的方式。

Fleet segregation and downtime: it has been documented for PEDV and more recently suggested for SVA that sale barns and slaughter plants are highly contaminated locations because the nature of their function. Due to the increased likelihood for contamination at collection points and slaughter facilities, tractors, trailers, and drivers are segregated between market and breeding stock movements. In the infrequent event where segregation is not feasible, an extended downtime of 72 hours is required after decontamination. Pig transfer and “drop and hook” procedures are used to facilitate segregation.

3.   清洗和消毒流程（清洗-消毒-干燥-检查）：每一个与PIC扩繁场或公猪站（GTC）接触的车辆，无论是内部还是外部农场运输，都必须在PIC认可的、遵从PIC生物安全方案的清洗和消毒中心进行清洗和消毒和干燥。清洗和消毒车辆也受到第三方检查。每次检查都是在移动设备上填写稽核内容，稽核完成后上传到一个健康数据库系统中。如果车辆未通过检查，则检查员可以提供问题区域的照片和书面评论。以上信息可用于培训员工，注意清洗中经常会错过的地方。除第三方检查外，驾驶员、农场员工和其他PIC人员都可以拒绝不符合我们清洗和消毒标准的车辆。

Decontamination process (Wash-Disinfect-Dry-Inspect): every trailer coming in contact with a PIC multiplier, for both internal and external movements, or gene transfer center (GTC) must be washed, disinfected and dried at a PIC approved facility that incorporates PIC biosecurity protocols. Third party inspections are also conducted on trailers. For each inspection, a mobile-based audit is completed and upload-ed into a health database system. If a trailer fails inspection, the inspector has the ability to provide a photo and written comments on the failed area(s). This information can be used to train employees on locations commonly missed during washing. In addition to third party inspections, drivers, farm employees, and other PIC personnel have the ability to reject a trailer not meeting our decontamination standards.

4.   装卸猪只的流程：驾驶员穿上塑料鞋套后方能下车，然后穿上防护服、干净的橡胶鞋或塑料鞋套，再进入装卸区域。“有序”的装车过程分阶段进行，分成三个界限清晰的区域，仅允许猪只单向流动。一名农场人员在被定义为清洁区的圈舍中赶猪，该区域末端是连接着转猪通道的围栏。农场的另一名员工在赶猪通道上工作，赶猪通道称为“过渡区”，末端连接着运输卡车。拉猪车称为“脏区”，任何农场人员不得进入。在过渡区（转猪通道）上工作的农场员工身着过渡区靴子和衣服，装完猪后需清洗和消毒转猪通道，脱掉衣服并洗完澡后才能返回农场。具体装猪流程请参见《猪译馆》文章《分段装车-防止污染物从拉猪车转移至猪舍》。

Loading and unloading process: drivers wear plastic shoe covers before stepping down from the cab and put on coveralls and clean rubber overshoes or plastic booties as they step into the cargo area. The “sequencing” loading process occurs in phases between three clearly demarcated areas. Only unidirectional pig transit is allowed. One operator will be working in the barn designated as the clean area which ends on a fence leading to the loading chute. A second farm employee will move the pigs through the chute which is designated as the transition area ending on the trailer. The trailer is designated as dirty no farm personnel can step onto it. The operator working on the transition area (chute) wears transition boots-clothing and after loading needs to wash-disinfect the chute, remove clothing and shower-in before returning to the farm.

风险评估、车辆分开、附加的消毒步骤、第三方检查以及对驾驶员、清洗和消毒中心人员和农场人员的培训及再培训，这些增加了运输过程的成本；但是，如果不做这些工作，疾病在扩繁场和客户场就有潜在爆发的可能性，从这个角度讲，以上投资是值得的。

The risk assessments, the segregation of the fleet, the additional decontamination steps, the third party inspections and training-retraining of drivers, truck wash crews and farm personnel add significant cost to the transportation process; however, the potential impact of disease outbreak in multiplication or customer herds justify this investment.