Biosecurity Barriers

Farm and system security are extremely important. Over the years, there have been many documented reports of pig thievery as a primary source of new disease entry into farms. It appears that these invasions often occur at multiple farms during the course of a single night, thus pigs are on the robbery transport vehicle from multiple sources, exposing each farm visited during the course of the night. Thieves aren't always just after pigs. Equipment and supplies are also targets, and pig farms are typically easy, low-risk targets. It is relatively simple to break into many farms in a single night.

Accidental disease entry may also occur if people enter a farm looking for employment or for other seemingly legitimate reasons. This situation occurs when there is no security against human entry. Warning signs are often overlooked, so lockable gates and doors that exclude entry during and after business hours are critical.

Perimeter fencing is more important for human exclusion than what was previously believed for domestic stock and wild animal exclusion. Although animal exclusion is important, people are the greater risk. Double security systems are best where the farm entrance has a lockable gate with a second, secured entry barrier at the barn entrance.

Showers are very good at preventing many disease agents. Enteric bacteria that are capable of infecting multiple species, such as salmonella, E.coli bacteria and other potential gut pathogens and most viral agents can easily be washed away. Detergent (soap) and water are tremendous barriers to new agent introduction, making a properly managed and designed shower entry a powerful deterrent for most swine diseases.

Other barriers, such as the “Danish” entry system, are also useful, but not as reliable as the shower facility. Boot exchanges prior to entering the shower area are adjuncts to the shower. They prevent tracking gross contamination into the shower area, but this space must be cleaned and disinfected routinely. Clothing change rooms are reasonable barriers, but don't reduce the risk of tracking as efficiently as the shower system.

Downtime rules have long been accepted by the swine industry as an effective method of risk reduction. The big question is, how long is long enough? For foreign visitors, they should be held out for at least five days after arrival in the United States. Many companies require a much longer period, especially for those visitors from high disease risk parts of the world. For most other service personnel, an overnight is enough if arriving in a clean vehicle, wearing clean clothing and entering through a shower protocol.

Other Risk Factors

Food, especially fresh pork cuts, processed pork and any smoked meats are especially dangerous if they come from outside the United States. Classical Swine Fever (hog cholera), pseudorabies, and FMD viruses can survive in smoked products and are especially viable in any fresh pork product derived from an infected pig.

Feed products, feed trucks, and people associated with feed manufacture and delivery are potential risk factors, but generally are a much lower risk than many of the above issues.

Feed manufacturers should observe good manufacturing practices of biosecurity. Routine screening for bacterial agents, toxins and other risk factors, such as molds, should be in place. Feed truck drivers should not enter any of the farm buildings, including the office. Deliveries should be made from outside the perimeter fence. A “mailbox” ticket system outside the perimeter fence for feed receipts prevents driver entry.

Commercial and internal waste haul and management equipment and personnel can potentially move pathogens from site to site. They should never enter a farm unless it is empty of pigs. They should wash and disinfect all external surfaces of their equipment and observe all farm biosecurity rules. It is best to have biosecurity discussions during contract deliberations. Recently, there have been unconfirmed reports of swine dysentery introduction into farms from waste management equipment.

Airborne disease introductions are only recently quantified by research and field investigations. This area of biosecurity research is in progress. Again, agent ecology and exclusion technologies must be understood before fully assessing intervention technologies. This requires field demonstrations, which are underway.

There is little doubt that airborne spread occurs and has been documented with FMD and PRRS virus. Viruses that are very resistant in the environment, reach high replication levels, and have unique ways of entering air flows and wind currents (dust, water droplets etc.), are likely candidates for this method of spread.

Much research has been conducted with the PRRS virus, and it does not appear to be an efficient airborne agent compared to many other viruses. Nevertheless, circumstantial evidence has led many to believe this is a major route of new virus introduction. Area spread is most likely a combination of many routes and factors, leaving actual airborne introductions in a lower but significant risk category. Airborne spread is likely seasonal, increasing in cold, wet conditions, and is of great consequence in pig-dense areas.

Service personnel and outside vendors are generally low on the risk hierarchy unless they travel from pig farm to pig farm. They should observe downtime rules (overnight), arrive in a clean and sanitized vehicle, shower in and out, and visually inspect and disinfect all tools and equipment.

Service veterinarians must also abide by the biosecurity rules. Veterinarians, because of their extensive training in disease management and biosecurity, could be considered a much lower risk than most other vendors. Even so, they must always conduct themselves with great scrutiny and effort at preventing any new agent introduction, including the more innocuous disease opportunists.

Next Page: Internal Biosecurity