Chapter 26 Carla Huston Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Starkville, Mississippi, USA The goal of dairy and beef breeding operations is to produce offspring for future production in the forms of meat, milk, or genetics. Subsequently, reproductive diseases can have detrimental effects on the reproductive efficiency of dairy and beef breeding herds. There are many infectious diseases that affect the reproductive performance in the bovine, including viral, bacterial, and parasitic. Specific pathogens may cause a range of clinical manifestations from metritis and infertility to abortion and perinatal loss. Biosecurity measures for a livestock operation are those taken to prevent the introduction or reintroduction of infectious disease agents into susceptible populations. While many biosecurity recommendations are good general management practices that can be applied across most operations, other recommendations should be more specifically tailored to an individual premises or group of animals. Biosecurity measures are undertaken at national, state, and local levels. At the national level, biosecurity plans are mandated by regulatory agencies such as the United States Department of Agriculture (USDA) and the United States Department of Homeland Security (USDHS) to protect livestock resources and consumer interests. Such plans are aimed at preventing the introduction of foreign animal diseases and other diseases of high economic consequence. The entry of animals, animal byproducts, germplasm (semen, embryos), and feed and feed products are carefully controlled at the national border. Producers and veterinarians participate at this level by adhering to recommendations following international travel and by reporting unusual or suspicious conditions to their state or federal animal health official. Biosecurity plans at the state level may focus on diseases targeted for eradication and control across state lines, such as brucellosis. State plans can also target diseases of regional significance, such as trichomoniasis, and are regulated through the state animal health official, most commonly the state veterinarian. Individual states may have different regulations for interstate animal imports, and both producers and veterinarians are responsible for knowing and adhering to a state’s specific animal health regulations. The issuance of certificates of veterinary inspection is one example of an important tool used to prevent the spread of livestock diseases across state lines. While disease control measures at the national and state levels are critical to the protection of the overall US livestock population, individual producers and veterinarians have the greatest influence over the implementation of local biosecurity measures. It is ultimately individual livestock producers who are responsible for protecting their own herd against infectious reproductive diseases. Local biosecurity plans focus on preventing or controlling the spread of disease between operations and take into account endemic diseases and conditions unique to that population of animals. Local plans should consist of both biosecurity measures as well as biocontainment measures, those taken to prevent or decrease the spread of a disease among groups of animals within an operation. Biological risk management (BRM) is the term used to describe the overall awareness and management of the risk of a pathogen or disease entering and spreading throughout a population. BRM often involves the evaluation, management, and reduction of pathogens that are already present on an operation. Some challenges to recognizing reproductive inefficiencies in a breeding herd include the lack of good reproductive records, the imperfection of diagnostic tests, and failure to identify the etiologies of abortions and perinatal losses. Furthermore, the intensive management of cattle in the United States, whether it is beef on pasture or dairy in confinement, creates challenges to ideal disease control conditions. Such challenges reinforce the importance for cattle producers to have a herd-specific biosecurity plan in place to protect their herd from reproductive diseases. A properly performed biosecurity risk analysis will help determine which biosecurity and biocontainment measures are appropriate for a specific operation. While general biosecurity measures are directed at nonspecific pathogen threats, a biosecurity risk analysis can be agent specific, industry specific, or event specific.1 Risk analyses can also be qualitative or quantitative, depending on the herd information available and desired outcome of the assessment. Many epidemiological tools are available to estimate the risk of specific disease transmission in a population, including statistical simulations and mathematical modeling.2,3 Such risk assessments should be made using multiple sources of information, such as producer surveys and diagnostic testing, to predict probabilities of disease transmission or to monitor progress following changes in management.4 A biosecurity risk analysis approach involves risk assessment, risk management, and risk communication, considerations which are all key to comprehensive and successful biosecurity planning. The risk analysis approach should center on specific epidemiological characteristics of the agent and host and environmental factors affecting reproductive health in the herd (Figure 26.1). A risk analysis for disease control is similar in concept to a hazard analysis and critical control point (HAACCP) system, which helps identify critical control points throughout the production chain where disease incursions may happen and incorporates control measures at each point. Whether a risk analysis or HAACCP system approach is used for protection against reproductive diseases, considerations should involve seeking input from not only producers and veterinarians but possibly also farm employees, family members, and economists. Figure 26.1 The risk analysis approach should center on specific epidemiological characteristics of the agent, host and environmental factors affecting reproductive health in the herd. It is commonly recognized in livestock production that every animal cannot be protected against every pathogen affecting reproduction. The purpose of a risk assessment in biosecurity planning for reproductive diseases is to evaluate the true likelihood, impacts, and consequences of an outbreak occurring in the herd. This involves hazard identification, exposure assessment, dose–response assessment, and risk characterization. The identification of hazards involves an examination of potential agents involved in reproductive diseases along with the population at risk, or susceptible hosts for disease. A risk assessment should contain estimates of reproductive disease threats, using past and current herd records for production (conception rate, calving rate, calving interval, etc.), and medical history, including vaccination practices and diagnostic testing, where available. Several infectious agents affecting reproduction should be considered in both beef and dairy herds in the United States, including viruses such as bovine herpesvirus type 1 (BHV-1) and bovine viral diarrhea virus (BVDV), bacteria such as Brucella abortus and Leptospira spp., and parasites such as Tritrichomonas foetus and Neospora caninum. Additional agents of concern are dependent on regional and environmental exposures. Host factors for susceptibility to reproductive diseases may be influenced by animal use, age, vaccination status, nutrition, body condition, and stress. Animals most at risk for reproductive diseases – the breeding females, breeding bulls, and replacement females – can be managed in ways to reduce reproductive disease risks. For example, the use of virgin animals will eliminate the risk of pathogens transmitted venereally such as Tritrichomonas foetus and Campylobacter fetus. It is useful to create a map of the farm environment during the initial biosecurity risk assessment to visualize the flow of animal and people traffic throughout the operation. The farm layout should include any buildings, pastures, working areas, feed storage areas, and water sources. Documenting the slope of the ground as well as the location of natural structures such as trees, streams and ponds can also help identify natural barriers for disease control. Nose-to-nose contact points should be identified in indoor as well as outdoor areas, paying special attention to sick pens, calving pens, and breeding areas. Visitor access areas should be clearly identified. Visualization of these areas and knowledge of associated risks will allow the creation of a flowchart to aid in identifying potential critical control points within an operation as well as identify potential entry points for new diseases.5 Exposure and dose–response assessments determine if the animals at risk are actually exposed to the identified pathogens, how often such exposure occurs, and how much exposure would cause a reproductive health risk to the animals. Environmental factors such as pasture management, animal contacts, and housing will have a great impact on pathogen exposure. Risk characterization examines the magnitude of the health risks, and how control of those risks should be prioritized. The end result of a properly performed biosecurity risk assessment is a risk determination where animal–pathogen–environment interactions are characterized as high, medium, or low priority for disease. The risk management stage of a risk analysis is often referred to as the “action stage.” The purpose of risk management is to establish measurable goals from the risk assessment, determine risk reduction strategies using the biosecurity tools that are available, implement biosecurity practices, and evaluate the implemented strategies. Available resources (personnel, equipment, financial), current biosecurity practices, and short- and long-term herd goals must be considered when developing risk management strategies. Goal-setting should include the level of aggressiveness desired and relies on good communication between all parties involved. For example, a less aggressive goal may be desired by the producer, such as cessation of abortions, while a more aggressive goal of a veterinarian might be to establish a herd free from persistent infection by BVD (BVD-PI). Management techniques to control reproductive diseases include a combination of tools such as movement control, diagnostic test and removal programs, vaccinations, and enhanced biosecurity measures discussed further in this chapter. Care must be taken to not implement too many changes in an operation at once such that an evaluation of impact cannot be accurately made. Furthermore, producers and employees may become overwhelmed with so many changes that none of them actually become implemented. The purpose of risk communication is to translate the results of the risk assessments and summarize risk reduction strategies to an easily understandable form. Proper communication requires interaction between all parties involved in the initial herd assessment. Additional education of team members and employee training is often indicated following risk assessment and management recommendations. Standard reproductive herd health protocols such as animal addition protocols, vaccination strategies, and visitor policies should be reviewed and provided in both oral dialogue and written form to have available for future reference. Communication methods can be very simple, such as a sign hanging in the calving barn, or very complex, such as the development of a statistical process control chart of reproductive efficiency.6 Regardless of the communication output chosen, it should be readily understandable to the end-user and updated when changes in management practices are made. Written biosecurity risk analyses or HAACCP plans, including treatment protocols and standard operating procedures, will also provide legal documentation if needed. While a myriad of biosecurity educational publications are available, most are nonspecific and contain wide variations in recommendations.7 Therefore it is important that biosecurity plans are tailored to farm-specific concerns. Furthermore, it is important to note that a proper risk analysis should be a flexible system, allowing for continuous monitoring, reevaluation, and open communication of all parties involved. The basic concept behind biosecurity and biocontainment recommendations is that diseases can be prevented or controlled by preventing effective animal contacts. This concept is even truer for reproductive diseases. Effective animal contacts are those contacts made by an uninfected animal that result in infection and disease. Effective animal contacts can be reduced by utilizing a combination of the following concepts: Controlling exposure to pathogens can be accomplished by implementing traffic control and proper cleaning and disinfection measures. The use of vaccinations and prophylactic medications can complement other pathogen reduction measures by reducing pathogen shedding and exposure. Reducing animal contacts may also involve traffic control and preventing fence-line contacts with outside herds. The use of artificial insemination (AI) and embryo transfer (ET) are two ways to reduce animal contacts in a breeding herd and also prevent exposure to many of the reproductive pathogens of concern. Optimizing animal immunity is accomplished by a variety of methods but should include management strategies such as providing good nutrition, reducing stress, and delivering an appropriate vaccination scheme.
Biosecurity and Biocontainment for Reproductive Pathogens
Introduction
Developing a biosecurity and biocontainment plan
Risk assessment
Risk management
Risk communication
Tools for intervention
Reducing effective animal contacts
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
