Biosecurity and Farm Security

Figure 62 Biosecurity on a pig farm Biosecurity on a pig farm

Introduction

Biosecurity of pigs at the farm level is the set of practical measures taken to prevent the entrance of infection into a pig farm and control the spread of infection within that farm. The goal of a biosecurity programme is to keep out pathogens that the herd has not been exposed to and to minimise the impact of endemic pathogens. Pig farm security can be defined as the planning and implementation of a programme to minimise various types of risk that can have detrimental effects on the farmstead and pigs. Biosecurity and security procedures are intertwined to enhance the health and productivity of pigs. Numerous factors are involved in the development and maintenance of a cost-effective programme for biosecurity. These factors can be thought of as links in a chain; a biosecurity programme is only as strong as its weakest link. The purpose of this publication is to provide information about the various aspects to consider when implementing and managing a biosecurity and farm security programme. It is not practical, nor is it recommended, for every farm to implement all of the procedures described. All farm biosecurity and security risk factors are unique to that farm and, thus, each biosecurity plan should be farm-specific. The best plans are created by working with a swine veterinarian or veterinary consultant who has extensive knowledge of the farm, employees, and local risk factors.

Biosecurity

The application of biosecurity measures differs among farms due to the geographic location of the farm, proximity to other pig farms, epidemiological situation (causes, distribution, and control of disease in the herd), type of swine operation, level of technology used for production, and whether other people are employed on the farm. The development and implementation of a biosecurity programme provides an essential component of many on-farm food safety programs; greater consumer acceptability of the quality and safety of the food supply; healthy animals that are more productive; improved animal welfare; and improved efficiency and profitability for the pork producer. In addition, supermarket buyers and consumers want pork producers to use less medication when producing pork.

Components of a pig farm required for adequate biosecurity

Biosecurity is made up of three separate, but often blended, sets of actions and overlapping components. These are:

bio-exclusion
bio-containment
bio-management

The goals of the production farm will determine how these are blended into a biosecurity plan. Pork producers focus on bio-exclusion and bio-management while neglecting bio-containment.

The purpose of bio-containment is preventing the spread of disease agents to neighbours or even long-distance transfer, but also the very important process of protecting the food supply for consumers. It is the single most important component of strategies that will be implemented if a foreign animal disease is introduced. Even though it is often ignored in day-to-day production biosecurity, this component is extremely important in any pig production system and often is the “right thing to do” for neighbours and other pig producers in a community.

Bio-exclusion is simply preventing the introduction of unwanted disease agents into the farm or system. This is where most producers focus and has been the focus of recent research.

Bio-management is the combined effort to control economically important infectious diseases that are already present in the farm population. Room disinfection, vaccines, all-in/all-out pig movement and many other procedures designed to reduce the pathogen level or enhance immunity levels in the pigs are key components of bio-management. Each of these areas can have a significant impact on the economic viability of a producer or producers in a geographically linked animal agriculture area.

Disease control is one of the most challenging areas for pork producers, regardless of whether the pigs are housed indoors or outdoors. Pork producers aim for minimal clinical disease status (bio-management) because it is economically and technically infeasible to exclude all important pathogens from a herd of swine. However, certain disease agents should always be excluded since bio-management methods are ineffective while exclusion opportunities are practical.

To develop a useful biosecurity plan, it is necessary to know:

The prevalence of diseases that can affect your herd.
How each disease is transmitted.
How each disease can be controlled.
How to prevent each disease from entering the herd.
The potential cost of an introduction and outbreak.

All biosecurity efforts come with a cost, and ineffectual methods should be avoided. Likewise, production practices that impose the greatest risk should be the focus, rather than low-risk activities. It is essential to have a swine veterinarian help develop a written and detailed biosecurity plan.

Biosecurity plans are intended to prevent adverse situations and improve the pork production business. All it takes is one breach of on-farm biosecurity to ruin a herd’s health status or that of a neighbour. This loss could have long-lasting and devastating production and financial effects on any farm. The following situations contribute the greatest risks to the health of pigs in a swine operation. These factors will be discussed later in more detail.

Adding new pigs to the farm without a quarantine period.
Failing to quarantine new additions for 30 to 60 days.
Failing to require testing for specific diseases prior to addition.
Failing to require vaccination for specific diseases before addition. Allowing pigs to return from fairs, shows, or exhibitions without quarantine and testing.
Allowing other domestic or wild animals to have contact with the pigs, feedstuffs, or water sources.
Failing to prevent disease transfer via pig transportation, human contact, other vehicular traffic, or equipment used with more than one animal or used at other locations such as a buying station, slaughter plant, or off-site farm.

It is common for small- and medium-sized pork operations to house their animals outdoors. Preventing the introduction of disease is difficult when pigs are housed outdoors or have access to outdoor lots because producers cannot control pig contact with wildlife, stray animals, rodents, insects, aerosols (containing disease agents), contaminated soil, and people. Feral and wild pigs are one of the greatest risks to outdoor producers since they carry most pig disease agents, including pseudorabies and brucellosis, which have been eradicated from U.S. and Canadian domestic pigs. Securing an outdoor facility is always challenging; however, various procedures can be used that discourage unwanted visitors and pests.

Prioritisation of Biosecurity Factors to Implement

Numerous factors can influence the biosecurity of pigs and farms. Some factors are more important to implement for biosecurity on small farms (with 100 sows or less). Farms with a small number of pigs typically do not have employees. Managers of small pig farms who work with a swine veterinarian and meticulously implement the following biosecurity principles generally have high herd health status:

Bring in only clean breeding stock verified by a swine veterinarian.
Always take extra care that biosecurity is a priority at the marketing access point and other trips to town.
Always make sure to keep boots, hands, pickup cab, and trailer in a clean zone so pathogens are not hauled home.
Use batch farrowing whereby all the pigs are moved at the same time and same age during each phase of production (weaning, nursery, grower, and finisher).
Make sure all tail-end pigs from the growing-finishing phase are moved off-site before a batch of sows will farrow.
Use the same breeding stock for four to eight parties.

When repopulating the sow herd, there are two options.

A. Option 1: Replacing Entire Sow Herd

Make sure the entire sow herd has been depopulated.
Make sure all pigs from the growing-finishing phase are marketed or moved off-site before replacement animals arrive on the farm.
If possible, have the depopulation period occur during the summer months to take advantage of the dry environment and high ultraviolet light period to help kill pathogens.
All replacements should come from a single source, which could be home-raised gilts or purchased females.
This option will affect cash flow due to lower productivity at the beginning and end of each turnover of the sow herd.
If pigs are finished indoors, the availability of space might be a problem during the middle of the high productivity period.

B. Option 2: Partial Replacement of Sow Herd

A proportion of the sows are replaced on a regular quarterly or longer period.
All the replacement animals should come from a single source (such as the original source of the sows being replaced).
The replacement source has the same health status as the farm. This requires monitoring of the source farm and communication, preferably veterinarian to veterinarian prior to receiving each group of replacement stock.
If possible, have the depopulation period occur during the summer months to take advantage of the dry environment and high ultraviolet light period to help kill pathogens.

Small Scale Farms

Small-scale piggeries are often at risk of spreading or contracting the disease as their biosecurity measures are non-existent. This provides information about numerous factors that can influence the biosecurity of pigs and farms. Some factors are more important to implement for biosecurity on small farms (with 100 sows or less). Farms with a small number of pigs typically do not have employees. Managers of small pig farms who work with a swine veterinarian and meticulously implement the following biosecurity principles generally have high herd health status:

Bring in only clean breeding stock verified by a swine veterinarian.
Always take extra care that biosecurity is a priority at the marketing access point and other trips to town.
Always make sure to keep boots, hands, pickup cab, and trailer in a clean zone so pathogens are not hauled home.
Use batch farrowing whereby all the pigs are moved at the same time and same age during each phase of production (weaning, nursery, grower, and finisher).
Make sure all tail-end pigs from the growing-finishing phase are moved off-site before a batch of sows will farrow.
Use the same breeding stock for four to eight parties.

Commercial Farms

Strategies for biosecurity of the pigs and farm should be developed by using a Hazard Analysis of Critical Control Point approach. Knowledge from scientifically applied field trial methodology, peer-reviewed publications, and significant field experience should be heavily relied upon when establishing the critical control points (CCP). Extensive interviews and inputs from all farm staff should be included in the early stages of the hazard analysis assessments. Without the participation of the farm employees, many CCPs (Critical Control Points) will be overlooked.

Once the CCPs are identified, then and only then can biosecurity interventions be developed. Only those evidence-based biosecurity interventions that have demonstrable usefulness in the field are applicable. Based on relative risk assessment, a hierarchy of biosecurity interventions can then be developed; in the end, focusing on those factors that have the greatest impact and opportunity for success.

A helpful formula for determining appropriate implementation decisions is the Appropriate Biosecurity Intervention Value, with the following formula:

Appropriate Biosecurity Intervention Value (BIV) =((DEV x RR)/DD) -IC

Where:

DEV = Disease Exclusion Value per pig per year (often very difficult to determine other than historical experience).
RR = The percent Risk Reduction per year for each intervention (from the PRRS Risk Assessment Tool and others).
DD = Degree of Difficulty (Ranking from 1 to 10 with 10 being very difficult).
IC = Intervention Cost per pig per year.

Using this formula, each agent and each intervention strategy can be qualitatively and semi-quantitatively analysed. These computations can then be used for choosing those strategies that have a final BIV greater than zero. Although arbitrary, the DD allows consideration of a customised score for the complexity of an intervention and the ability of the farm staff to adopt, implement, and sustain an intervention procedure or process. It becomes farm or system-specific, which is ideal in the real world. If several diseases have similar risk reduction for the same intervention, the DEVs can be added and the sum entered into the equation. As multiple agents are considered, the strength of the intervention strategy becomes apparent. Of course, not all the risk factors, values of disease exclusion, or the percent RR are known, but a veterinarian can arrive at reasonable approximations by using the risk assessment tool (Holtkamp et al., 2011), published information, and biosecurity experts.

Developing a value equation for each disease is often a matter of benchmarking diseased pigs with those that are free of disease in the same system. Some average disease cost numbers are published for the porcine reproductive and respiratory syndrome (PRRS) (Neumann et al., 2005), transmissible gastroenteritis (TGE) (Mullan et al., 1994; Regula et al., 2000), Actinobacillus pleuropneumonia (Losinger, 2005), and Mycoplasma hyopneumoniae (Maes, 1999). These estimates for the cost of disease are useful benchmarks. The amount of RR for each biosecurity intervention and the perceived value for exclusion help arrive at a logical expectation for those interventions. With this approach, only those interventions that have a value greater than zero are applied.

Calculating IC can be difficult and often relies on farm or industry experience. The cost of building a shower facility is relatively straightforward, but the variable costs associated with implementing showers for all who enter the farm are highly variable. Clothing costs and frequency of replacement; increased use of water, shampoo, soap, the washing machine, clothes dryer, and electricity; employee lost work time; morale; employee retention; and many other details should be objectively considered and calculated. Comparing this to a boot and outerwear exchange facility (Danish entry) is worth considering, especially for smaller operations. Downtime rules often create significant costs but have very limited exclusion value. Determining IC for downtime rules is difficult but no more difficult than the calculation of its DEV. Establishing universal DEV and IC for each economically important disease agent is worthy of considerable research dollars. For example, calculating the value of barn filtration also may be a daunting task, but disease (PRRS) exclusion must be near 100 percent with current filtration application and maintenance costs.

Location of Farm

One of the main factors that increases the risk of a herd acquiring a new disease is often the proximity of the farm to other live pigs. The nearby presence of growing pigs is a much greater risk compared to a breeding herd that sends all weaned pigs to an off-site facility. Theoretically, pig production facilities should be located as far as possible from other pig facilities. Table 1 indicates factors influencing the risk of a breakdown in a biosecurity programme due to the location of a pig farm. Although location is important, factors within the farm can influence all aspects of biosecurity. The positioning of buildings within the unit, the position of ventilation inlets and outlets, people movement, isolation procedures, pig movement, and other factors will affect the success of biosecurity plans.

Factors influencing the risk of a breakdown in the biosecurity programme due to the location of the pig farm:

Pig farms nearby: A farm with 500 animals (sows, nursery pigs, and growing-finishing pigs) at a distance of 9 km away represents less risk than a herd of 5 000 at 1.9 km away. If the 5 000 animals are a breeding herd, the risk is much lower compared to a finishing site with 5 000 growing pigs. Locating your outdoor pig production unit at least 3 km from other swine could minimise the risk of infection by aerosol and other natural routes of transmission. Although aerosol transmission does occur with some agents, it is probably extremely rare for most agents.
Other possible sources of contamination: A slaughter facility at less than 9 km away represents an enormous health risk, whereas at greater than 9 km, the risk is reduced. Rubbish dumps represent a biosecurity risk when situated at less than 9 km. The manner in which nearby pig facilities are managed for vegetation growth, drainage from the farm, and biosecurity procedures can influence the risk of a breakdown in the biosecurity of other pig farms in the area.
Type of ground: Ideally, the land should be hilly and protected from winds. Flat land without trees or other kinds of protection would have a higher level of aerosol risk compared to hilly land.
Roads: A road with a high density of vehicles transporting pigs at less than 50 meters from the herd represents an important contamination risk. Distances more than 22 km to 45 km from the herd greatly minimise biosecurity risk. However, some breeding stock companies have concluded that transport risk associated with driving near pig sites along a route or in-route exposure to vehicles hauling slaughter pigs appears to be very low.
Other animals: The presence of cattle, sheep, or poultry could be a biosecurity risk if housed at a distance of less than 100 m.
Climate: During optimal climatic conditions (such as winter months, high humidity levels, constant moderate winds, and flat land), windborne dust or aerosol droplets present in the air can infect swine. Cold and humid climates are more favourable to disease transmission than dry and hot days. Aerosol spread of pathogens is usually reported to occur up to approximately 1.8 km around an infected farm. Many viruses like cold, dark, and wet conditions. TGE and PRRS viruses are susceptible to drying, ultraviolet light, and heat. Movement by aerosol likely occurs at night under very specific conditions; thus, aerosol transmission is rare. Concerning PRRSV, one aerosol transmission every two years is still a big issue for a producer in harm’s way.

Sources of Swine Diseases

Swine diseases are a concern for nearly every pork producer, regardless of the size of the operation. A disease outbreak can be economically devastating to a swine operation. People involved with pork production must understand how swine diseases are spread and how people can influence the spread of diseases among pigs and farms. Swine disease can be spread in several ways, including:

Through diseased swine or healthy swine incubating disease, or unaffected
Through new replacement gilts and boars.
Purchased semen.
Through other farm animals, insects, pets, birds, and wild animals.
On the clothing and shoes of visitors and employees moving from farm to farm.
On employees who did not follow all the biosecurity procedures of the farm.
Any employee or visitor who has had recent direct contact with other pigs.
On contaminated feed, water, bedding, and soil.
From the carcasses of dead animals.
On contaminated equipment and vehicles used on the farm.
On contaminated veterinary equipment.
Any equipment that has been in contact with pigs from another site.
On contaminated commercial vehicles hauling culls, slaughtering, or growing pigs.
Delivering feed (truck and even more so the driver) in airborne particles and dust blown by the wind, and on consumable supplies entering the farm.

Unexplained disease transmission over short distances is often attributed to aerosol infection. Aerosol and airborne spread of infections depends on numerous factors, such as the type of pathogen, number and density of animals excreting and susceptible to infection, method of housing, droplet size, relative humidity, ambient temperature, ventilation fans, wind speed, wind direction, sunlight, topography, natural barriers, and methods of manure application. Although a minimum distance of 1.8 km between neighbouring pig farms is desirable to limit the risk of aerosol disease spread, this may be impractical for existing pig farms. Often, disease agents have other routes of transmission that are more important and more frequent compared to aerosols but just as difficult to document. Like aerosols, distance from other pigs is also an effective deterrent against these methods. Distance has a dilution effect on all pathogens by reducing the likelihood of all means of transmission. The risk of aerosol is also related to the number of pigs on the distant sites. Large numbers of growing pigs increase the odds of a random introduction. There have been outbreak investigations that imply aerosol movements up to 4.5 km with the PRRS virus and as much as 1.8 km for Mycoplasma. Aerosol transmissions are very difficult to substantiate but likely occur in special weather-related situations.

Purchasing Replacement Gilts and Boars

Finding a source of minimal disease animals is not always easy. Essential elements of a biosecurity programme are often ignored in small pork operations, such as procurement of new breeding animals from a reliable source and isolation of new animals before introduction into the herd. Word of mouth and testimonials often take precedence rather than direct veterinary knowledge from health monitoring and pathogen testing. Direct contact with other pigs is always the greatest risk for acquiring new diseases.

The following guidelines are suggested when purchasing replacement gilts and boars:

Know the disease status of both recipient and source herds.
Consider the location and health history of the source herd.
Select replacement gilts from a single source that has a documented genetic improvement programme and sound disease control (biosecurity) programs.
Select replacement boars from a single source that has a documented genetic improvement programme and sound disease control (biosecurity) programs.
Most breeding companies utilise a veterinarian and maintain an internal health recording programme. Have your veterinarian consult with the source herd’s veterinarian to:
confirm that the source herd has not had any recent disease outbreaks,
determine what diseases have or have not been detected or tested for in the source herd,
determine what vaccination programs are used, and
determine what antimicrobials are being used in the feed or water.

Maintain animal movement records. List the contact information of the seller(s), the origin of the pigs, the number of pigs purchased, the date pigs are moved onto your farm, and, if available, the premise identification.

In principle, fewer introductions of new gilts and boars into the herd would seem to reduce the odds of bringing a disease into the herd. However, the parity distribution and genetic improvement cost of infrequent introductions may offset the risk, especially if a good single source of replacement animals is involved.

The risk of disease transmission is minimised when:

There is open communication between the producer’s veterinarian and the source herd’s veterinarian.
All new replacement animals are brought into the herd after spending 30 to 40 days in a biosecure isolation facility that has an excellent and functioning disease monitoring or detection programme in place.

Artificial Insemination

The alternative to purchasing replacement animals is to utilise a closed-herd policy. Artificial insemination is the easiest method to bring new genes into a sow herd. However, biosecurity risks can be associated with artificial insemination. Boar semen can contain various potential pathogens, such as Porcine Reproductive and Respiratory Syndrome Virus and Porcine Circovirus. Most boar studs routinely test semen from AI boars for the presence of PRRSV and only bring in negative boars that have never been exposed to PRRSV.

Generally, semen arrives at the farm by either a boar stud courier or an external courier. Semen shipped via an external courier is normally packaged and sealed into a temperature-controlled 17.22°C, double-boxed Styrofoam container. Semen delivered by a boar stud courier is generally transported in paper or plastic bags placed in a cooler during transport. When the courier arrives at the farm, the bags of semen are removed from the courier and placed in a semen cooler with a temperature of 17.22°C. The semen cooler is located in the “dirty” area of the farm.

All semen packaging (bags, Styrofoam cooler, and so forth) should remain outside the farm. Only the semen should enter by passing across the dean-dirty barrier. Although the semen source may be free of those disease agents generally considered economically critical like the PRRS virus, other pathogens may be present, and a contaminated cooler could bring in unwanted bacteria or virus agents from the boar stud. Likewise, the courier should never enter the farm because his or her route is unknown, and a courier would not have knowledge of potential disease agents that may be present at other drop destinations. Generally, an area outside the dean-dirty barrier is designated for drop-off. This can be off-site at the producer’s house or other location. In the latter situation, the producer may place the semen into a shuttle cooler to move to the farm. Before showering into the pork production facility, move the doses of semen from the shuttle cooler across the dean-dirty barrier into an appropriate container, such as a Styrofoam cooler. After showering, place the doses of semen into the farm’s semen cooler.

When delivered by a courier directly from the stud, a dirty side semen refrigerator is often placed where the semen can be delivered after hours. Once again, this could be off-site. In this case, the semen should be double bagged so that any potential contamination that could occur during the courier’s route will most likely be in the outer bag. The outer bag is often paper with a plastic bag with the semen placed inside and stapled by the boar stud employee who packages the semen for shipment. When placing the semen in the refrigerator, the courier first will take the two-bag package out of the vehicle cooler. The second step is pulling the inner bag out and placing it in the refrigerator. The outer bag goes back to the vehicle and is placed in a rubbish bag and discarded at an off-site trash collection location. This bag should never return to the stud or be left at the delivery point. When the semen is needed on the farm, personnel dump the semen across the dean-dirty barrier, only touching the bag. This bag is disposed of outside the farm. Some farms spray disinfectant on all supplies, including semen containers, entering the farm as they pass the dean-dirty barrier.

Isolation of Incoming Pigs

Pork producers should discuss with their veterinarian the procedures to use during isolation and acclimation of the replacement gilts and boars. Regardless of whether a pork producer is purchasing replacement animals from the same genetic supplier and health monitoring programme, an isolation facility and programme should be in place. Because the incubation period for different disease agents is highly variable and the replacements may not exhibit any signs of sickness for some time, these replacements must remain in quarantine until test results and observation give reasonable assurance that they are healthy.

The quarantine period also allows the source herd to discover any new disease introduced into that herd. In addition, contamination could have occurred during transportation. Incoming gilts or boars must undergo a period of isolation for 30 to 60 days. The duration of isolation will depend on the specifications set by your veterinarian and the particular disease(s) of concern. Isolation allows pigs to recover from the stress of transport to the farm, adapt to a new environment, and any incubating infections to become evident.

The period of isolation provides an opportunity for the inspection of animals by a veterinarian, a laboratory analysis of blood samples for diseases, and vaccination of animals before entering the herd. Guidelines for isolation units are:

Make sure that the biosecurity of the isolation facility is at least as good as the biosecurity of the main herd.
The isolation unit should be in a location that is as far from other area pigs as possible, ideally more than 2 miles from the nearest neighbouring pig facility. The ideal distance from the isolation facility can vary depending on the management, testing protocols, biosecurity precautions, number of replacements in each quarantined group, and the disease(s) that are to be prevented. Work with your veterinarian to determine the best location in any specific situation.
The isolation facility should prevent direct contact with all other pigs, domestic livestock, and wildlife. Where appropriate, a security fence should be erected around the isolation unit.
The isolation facility should provide an air space, a water source, and a feed source that are separate from all other pigs and livestock.
The isolation unit should be operated on an all-in/all-out basis.
The risks of manure storage and drainage on disease transmission should be eliminated. Isolation facilities should have their own manure-handling facilities.
The isolation facility should provide a clean, dry, comfortable resting space for all the pigs.
When appropriate, animals should be provided with clean and dry bedding.
Animals should be provided with clean and readily available water.
During summer months, it may be necessary to move gilts housed outdoors to an area that will prevent sunburn. White-coloured gilts can get severely sunburned.
Where possible, use a separate person and equipment in the isolation unit. If one person cannot be dedicated to taking care of the isolation unit, the unit should be the last work task of the day. This person should shower, if possible, and put on clean clothes and boots prior to entering the isolation unit. Many successful isolation facilities have no showers, and the farmer checks the animals on the way to the house. A boot exchange, isolation-specific coveralls, and hand washing are highly effective. Make sure the indoor facility has good lighting and accessibility of animals for visual inspection.
The isolation facility should provide adequate restraint facilities for examinations and administration of treatments.
The isolation facility should have an equipment and storage area. This equipment (such as boots, clothing, scrapers, shovels, buckets, and so forth) is only used in the isolation area.
All animals should be closely observed each day for clinical signs of any disease, including coughing, excessive sneezing, diarrhoea, blood or mucus in the faeces, loss of appetite, skin lesions, or lameness. Rectal temperatures should be taken in pigs that show any of these signs. Any abrupt changes in behaviour or onset of clinical problems should be immediately reported to the veterinarian.
Your veterinarian should visit the isolation area for blood sampling and inspections of animals. Depending on the diseases that are to be excluded and the nature of test diagnostics utilised, sampling shortly after arrival and again three to four weeks later may be necessary to assure freedom from disease. Allow enough time for laboratory results and expect to retest on occasion.
When possible, an acclimation programme to the diseases on your farm should start in the isolation facility. Make sure the isolation facility is easy to clean and disinfect between batches of replacement animals. The cleaned and disinfected facility should remain empty and be allowed to completely dry before the next entry. This usually takes two weeks but can be shortened with heated drying.