BIOSECURITY FOR PASTURED PIGS

By: Joshua Schaeffer

The root meaning of biosecurity is the securing or preserving of life. In an agricultural setting, the term is used to describe measures put in place to control exposure to pathogens, or disease causing entities, such as bacteria, viruses, fungi, or parasites. Many in the swine sector talk about ‘internal’ and ‘external’ biosecurity. There are three main biosecurity goals:

• Prevent pathogens from entering the farm (bio-exclusion, external biosecurity).
• Prevent the spread of pathogens from one part of the farm to another (bio-containment, internal biosecurity).
• Decrease the severity of disease through controlled exposure and/or vaccination (bio-management, internal biosecurity).

These goals are met through either eliminating or minimizing the modes of transmission for pathogens. Instead of focusing on biosecurity practices for each disease, this document will highlight the different modes of transmission and factors that affect the risks associated with each. Veterinary input is crucial to the development of a biosecurity plan, especially when considering controlling risk factors for a certain disease.

Fomites
A fomite is any inanimate object capable of carrying an infectious pathogen from one individual pig or farm to another. Fomites can be responsible for the introduction and spread of many diseases of pigs. On a swine operation, this can include any equipment being used, boots, clothing, vehicles and also feeders and waterers.
Several production practices can be implemented to decrease the risk of transmission through fomites. In an ideal setting, boots and coveralls would be changed before going from one group of pigs to another, though under many settings, this is not a viable option. A good alternative is to develop a work schedule that follows pig flow from the ‘cleanest’ to the ‘dirtiest’ pigs. Work with your veterinarian to determine where each group of pigs on your farm fits on this health continuum. (e.g., Farrowing à Gestation à Nursery à Grower à Finisher). Many veterinarians will consider nursery pigs the most susceptible because the immunity they have from colostrum is wearing off and their own immune system is not yet mature. Any group of pigs that is known to be suffering from disease should be left until last. Any pigs in isolation would also fall to the end of the list to minimize risk of transmitting pathogens they may have to other pigs on your farm.  If the chores cannot be done in this order, then having separate boots for each phase, or at least cleaning boots of any organic material and disinfecting them between groups, is recommended.

Access of visitors to your farm, proximity of your farm to other, nearby farms, and the cleaning and disinfecting of equipment are some of the most important factors to consider in developing a biosecurity plan. Any boots or equipment being used should be cleaned and sanitized after use and before use on another group of pigs. Any livestock hauling equipment, such as trailers, should be thoroughly cleaned and disinfected after each use. When using a disinfectant, it is necessary to remove organic matter (manure, bedding) prior to application of the disinfectant, as most disinfectants do not work in the presence of organic debris. Manufacturer instructions on the use of the disinfectant should be followed carefully, not only to ensure efficacy, but also to prevent any unwanted human or animal health risks. When handled according to manufacturer instructions, a 5% solution of bleach is an economical and readily available disinfectant and can be used in the sanitation rotation.

Aerosols
Depending upon the pathogen and environmental conditions, disease can be spread through the air over a considerable distance, in some instances, up to 10 miles. Location is a key biosecurity plan component for outdoor swine operations. Ideally, the farm should not be located within close proximity to major roads on which swine are routinely hauled or close to other swine operations. Hilly topography and windbreaks can be helpful in disrupting the air currents; thus, they can be used to decrease the distance that pathogens can travel through the air.

Oral
Ingestion of infectious pathogens is a major mode of transmission for disease. Clean, fresh water should be provided to promote good animal welfare. Preferably, water from a water treatment facility should be utilized, but a deep well may be an acceptable water source. Using surface water, such as ponds, as a water source for pigs increases the risk of exposure to oral pathogens. Feed can also become contaminated and serve as a source of disease. Feedstuffs should be purchased from a reputable source and stored properly to prevent spoilage and rodent/pest access. To prevent contamination, do not use feed handling and processing equipment for other purposes unless they are thoroughly cleaned and disinfected before being used again for feed. Just like the feedstuffs, bedding materials should be obtained from a reputable source and stored appropriately to prevent contamination. Dirty bedding and manure should be removed regularly from confinement and feeding areas.  Waste material should then either be hauled from the swine areas or stored/composted in a manner to prevent pig exposure. When handling waste, it is important to follow all federal, state, and local regulations. Waste management is also important when developing biosecurity plans for pastured pigs. Pastures should be designed and managed to minimize exposure to manure, and to prevent runoff from rains. Density (the number of pigs in a given area), frequency of pasture rotation, and the length of time a pasture is idle before pigs are returned to it are important management tools for minimizing infectious diseases.

Although not considered a source of transmission, colostrum management is important in decreasing the risk of disease in baby pigs. Colostrum, or the first milk, contains concentrated amounts of antibodies that are absorbed across the gut wall of the baby pig following consumption. To ensure colostral protection, it is important that pigs nurse within the first 12 hours of life. Furthermore, correct vaccination of the sow is needed to ensure adequate antibody levels in the colostrum.

Direct Contact
Pigs can become sick by having direct contact with other pigs, even when there are no signs of illness. The best method to control this mode of transmission is to practice all-in/all-out. Pigs that are at different stages of production (farrowing, gestation, nursery, grower, finisher) should be housed separately. Fencing and housing should be designed to eliminate any possibility for nose-to-nose contact from one group to another. Furthermore, animals should move as a group through the production cycle to limit disease transmission.

Purchased animals, and animals that leave the farm and return, should be quarantined for a minimum of 30 days before being placed in the general population. A veterinarian should be consulted to determine if any testing should be performed on these animals to prior to entry to the production site. New pigs should be acclimated to the herd by moving pigs from your herd into a pen adjacent to the new pigs before they are allowed to enter the herd. This is commonly done at the quarantine facility after the isolation period. This allows the new pigs to become exposed to pathogens that are endemic in the existing herd and to develop an immune response to them.

Vaccination
Technically a form of direct contact, vaccination is the key component for bio-management in a biosecurity plan. Vaccination aids in the control of disease by exposing the pig’s immune system to small doses of either a weakened or killed pathogen. When an immunized pig becomes infected with the natural pathogen, the immune system can mount an efficient response to control or kill the now familiar pathogen.  When implemented correctly, vaccination protocols can minimize and even eliminate the clinical signs of several diseases. To ensure efficacy, vaccine label instructions on handling and administration of the vaccine should be followed carefully. In addition, working closely with a veterinarian to determine what vaccines to use and when to administer them is important for developing an effective vaccination protocol. Table 3 lists some commonly recommended vaccines.

Table 3. Some common vaccines for pigs

Vectors
A vector is a living organism that transmits disease from one individual to another.  Biting insects, such as ticks and flies, are some of the most common examples of vectors, as they can potentially spread many pathogens directly. However, potential vectors on a swine operation also include rodents, birds, and other mammals. These vectors can either spread pathogens directly (for example, Sarcocystis spp. in dog feces) or indirectly (for example, transmissible gastroenteritis virus on contaminated feathers). Pigs housed outdoors have increased exposure to vectors.  To help control spread and introduction of disease, measures should be taken to control or deter rodents, insects and birds in feeding areas. Also, pigs raised in dry lots should be housed separately from other livestock; from a purely swine health standpoint, contact with all other animals would be avoided, though this may be impractical in many settings.

Feral swine are a particular risk that must be considered for pigs housed outdoors.  Feral pigs have the potential to transmit any number of diseases to domestic pigs and two of these, brucellosis and pseudorabies, are a true threat to outdoor pigs. These diseases have been eradicated from domestic pigs but are still present in the feral population. When raising pigs in an area where feral swine are present, well-structured double-fencing is needed to prevent contact between domestic and feral swine.

Zoonotic & Anthroponotic Diseases
There are several diseases that can be transmitted from pigs to people (zoonotic diseases) and diseases that can be transmitted from people to pigs (anthroponotic diseases). For example, some flu viruses can be transmitted between pigs and people. Practicing good personal hygiene and using personal protective equipment (clean coveralls and boots, gloves, masks, etc.) can greatly decrease the risk of transmission. Good hygiene practices include frequent washing of the hands and not eating, drinking or smoking when working with pigs. To prevent spreading disease from people to pigs, people who are ill should not be near pigs and should preferably not be on the production site. If a worker is ill, he should contact a physician for medical care and inform the physician that he works with pigs and whether or not the pigs have been sick recently. Personal protective equipment should be used when directly handling sick pigs, carcasses, or cleaning contaminated equipment and quarters. It should also be used by farmers who are sick and have nobody to replace them for farm chores.

Conclusion
A biosecurity plan is vital to control disease transmission on swine operations. Regardless of the type of operation, measures can and should be put in place to control disease. For example, one of the first steps in establishing some degree of biosecurity on any farm is to dedicate a separate pair of boots and coveralls for pig chores and clean these frequently. There is no one-size-fits-all approach to biosecurity. As a result, it is vital that a veterinarian be employed to develop biosecurity protocols based on the type of operation, available labor and capital, and diseases of concern.

For more help understanding biosecurity, and resources to aid you in developing your own biosecurity plan, check out these links:
The Livestock Conservancy biosecurity resources:  https://livestockconservancy.org/resources/biosecurity/ 
Biosecurity for today’s swine operation, Seaman JS and Fangman TJ, University of Missouri Extention publication G2340.  https://extension.missouri.edu/publications/G2340
Biosecurity of Pigs and Farm Security.  Levis DG and Baker DB, University of Nebraska Extension publication EC289.  http://ianrpubs.unl.edu/live/ec289/build/ec289.pdf
Iowa Pork Industry Center Publications,  http://www.ipic.iastate.edu/publications.html
Pork Information Gateway.  www.porkgateway.org
Good Practices For Biosecurity in the Pig Sector. FAO Animal Production and Health Paper 169.  http://www.fao.org/3/a-i1435e.pdf