Most diseases are spread from pig to pig; however, diseases can be spread in other ways. All it takes is one breach of on-farm biosecurity to ruin a herd's health status. For large farms this loss could have long-lasting and devastating effects because the practicalities of disease eradication becomes increasingly difficult as herd size increases. Not only is the total cost higher but the logistics of replacing gilts are prohibitive.
Key elements of a piggery biosecurity program
- Isolation from other farms
- Controlled entry (for all visitors and to keep animals, including feral pigs, out) - use a ringlock mesh fence (or similar) 1 m high with lockable gates
- Operate a closed-herd (using artificial insemination) or buy-in replacement breeding stock from a single source. The stock should be from a herd of higher or comparable health status
- Use a load-out area which is clearly defined as off-farm
- Use off-farm isolation or a quarantine facility and simple disease transmission and prevention protocols
- Enforce the use of a single, controlled entrance for staff and visitors that clearly separates 'clean' piggery areas from 'dirty' non-piggery areas
- Provide an area to change into farm clothes and boots that is clearly separated from the 'dirty' non-piggery areas
- Provide training programs for staff about disease control
The most fundamental principle of disease control is to use replacement breeding stock from a single source. The other alternative is to practise a closed-herd where improved genes are introduced through artificial insemination (AI).
Isolation sheds on-farm or at another site can be used to provide a basic quarantine facility and combined with protocols are a simple disease-entry prevention measure.
Quarantining new breeding stock can protect a herd against mange, Actinobacillus pleuropneumoniae (APP) and swine dysentery (SD). Even if mange, Mycoplasma hyopneumoniae and APP serovar 15 are not an issue for most farms (because the herd is already infected), SD and APP 1 are an issue. M. hyopneumoniae, APP, SD, mange and progressive atrophic rhinitis (PAR) have all been spread to herds from seed stock producers in Australia. Leptospirosis may also have been spread this way.
For herds free of M. hyopneumoniae, isolation facilities provide a measure of insurance and protection. Some episodes of M. hyopneumoniae infection have not been prevented by isolation because the disease was not immediately identified in the source herd; therefore, an eight-week isolation period is recommended. The isolation period can be combined with serology testing but the logistics and the uncertainty of interpreting the results (at least for M. hyopneumoniae) make it too complex for even sophisticated management, so the tendency is to rely on clinical signs and slaughter checks of the source herd.
Visitors and visiting
Have only one point of entry for visitors and keep a visitors' log. Clearly signpost the point of entry and ensure staff follow the same entry rules that apply for visitors.
Despite common perceptions, researchers have shown that people are rarely true carriers of pig pathogens under circumstances that would permit transmission back to pigs. Extra precautions in biosecurity such as the 48-hour rule are important overseas where they have viruses such as foot and mouth disease (FMD). The FMD virus has been recovered from the noses of people working with FMD-infected animals after 28 hours of contact but not after 48 hours, which is where the 48-hour rule some piggeries follow comes from. The 48-hour rule requires visitors to spend 48 hours away from all pigs before entering the piggery, however, in Australia this is not necessary for most herds and their local visitors.
Pig-free 12 hours
Some farm operators insist that essential visitors and staff, who come into contact with pigs or people from other pig farms, have extended periods away from their pigs. There is no basis for this recommendation. This recommendation has failed to protect herds against disease incursions and probably hinders production rather than helps it. The disease-prevention priorities are out of step when some herds have a four-day pig-clean entry rule yet buy pigs from many sources (a single source of supply is recommended).
Because of the consequences of introducing diseases it is not unreasonable to implement a pig-free period of up to 12 hours (or overnight) and a shower-in policy for visitors to some high health status herds; however, some research has shown that shower-in facilities provide no additional protection.
Clean boots and clothes, equipment
A change of boots and clothing provided at the farm gives a necessary layer of protection from any diseases that may be carried by people. This, combined with separate 'clean' and 'dirty' areas, is all that is required. Some infectious agents will survive in faeces and mucus on boots and clothing. Make sure you clean and disinfect equipment that is to be moved or used between farms.
The successful Danish system for visitors
- Walk in the door to the change room that leads to the piggery.
- Remove your top clothes and shoes and leave them in the designated dirty side of the change room.
- Walk onto/over the grate that separates the dirty area from the clean area.
- Wash your hands thoroughly with soap and water and scrub under the nails.
- Walk off the grate - this denotes going into the designated clean area. Put on the farm clothes and boots provided.
- As you exit the change area you may be required to walk through a footbath containing disinfectant or to scrub your boots with a scrubbing brush and disinfectant (emphasising that you are in the clean area) before going into the piggery.
Footbaths have been shown to be practically useless in eliminating bacterial contamination. For most farms it will be enough for the farm boots to be clean.
Domestic animals present few risks as far as the target diseases are concerned. Dogs seem only to present a risk if they travel to different farms or their 'own' farm undergoes an eradication program e.g. SD, salmonella. Birds are unimportant in an Australian pig disease transmission context.
Vehicles are only a risk if carrying pigs or if not cleaned before they arrive on farm to collect pigs. A race leading to a loading ramp a minimum of 20 m, preferably 50 m, from the piggery is desirable.
Staff training programs are important elements of biosecurity and some suggest that creating some biosecurity hurdles that staff must endure (e.g0 shower-in) reinforces biosecurity awareness.
Exotic pig diseases
In other parts of the world porcine reproductive and respiratory syndrome (PRRS), Aujeszky's disease, classical swine fever, African swine fever, swine influenza, transmissible gastroenteritis and FMD demand additional levels of biosecurity but Australia can take advantage of its health status in this regard unless a change in the situation occurs.
Talk with your veterinarian to tailor your biosecurity program for your herd.
Cutler R (2001) 'Review: eradicating pig diseases in Australia', from Manipulating Pig Production VIII, proceedings of the Australasian Pig Science Association conference, ed. P D Cranwell. This resource may be purchased from the Australasian Pig Science Association.
Cutler R ed. (2001) Biosecurity chapter in 'Eradicating diseases of pigs', Australian Pork Limited. This book may be purchased from the Australasian Pig Science Association.