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By Dr Dirk Verwoerd, Pfizer Animal Health, on behalf of the Pig Vet Society

Biosecurity has become one of the buzz-words of our time; consider sensational media reports and strategies to combat intentional (eg bioterrorism attacks in the USA using Anthrax spores via the Postal system) or non-intentional (e.g spread of SARS virus infection via international air travel) introductions of human disease —causing micro-organisms.

Also in our own industry, as part of preventative measures against insidious disease syndromes such as PMWS. We are tempted to think that this is a modern concept, but biosecurity principles were established as long ago as in the Old Testament hygiene rules described in the Bible, while history records the first written municipal ordinances that describe a 30 day quarantine for visiting sailors in the harbour city of Dubrovnik, Croatia, in 1348. A more dramatic example of a breach in biosecurity occurred during the first recorded biological warfare event.

The Mongols lead by a grandson of Genghis Khan besieged the harbour city of Caffa in the 1340’s and responded to high mortalities due to an outbreak of Bubonic Plaque amongst their own soldiers, by throwing their dead (infected) bodies over the city walls using so-called "siege-machines". This caused a similar outbreak in the confined city, and resulted in the rapid evacuation by sea of all surviving inhabitants.

One of the most graphic recent examples of extreme biosecurity measures was the "stamping out" (kill & burn) approach to the devastating Foot-and-Mouth Disease epidemic in the United Kingdom a few years ago.

Each farm/animal production facility is an ecosystem, and our challenge is often to keep all the different members of this system in an economical harmony with each other.

In practical terms, applicable to your own pig farm, these biosecurity measures can be summarized as follows:

Movement/access control

• Pigs: The closer one can operate to the ideal of complete "all-in-all out", the better. Even where the farm design or infrastructure forces us to follow multi-age production strategies, one can achieve major advantages by dedication of houses to more uniform groups, adjusting the schedule of movements between houses, etc. Managers, etc that have to visit different sections should always move from young to old, not vice versa. Older pigs have developed immunity to agents that will still infect the young ones. Sections can be "colour coded" to reflect this eg farrowing houses = Red; Weaner houses = Yellow; Older pigs = Green. Coloured overalls that reflect this scheme can allow the manager to immediately spot workers breaking the "best practice" rules. This procedure is common on poultry breeder farms and high health status pig herds.

• People and other animals/birds: Management, labourers, visitors; showers, washrooms, dedicated (different colours!?) overalls & rubber boots; continious rodent control, bird unfriendly infrastructure, no use of untreated surface water for either washing or drinking (wild birds, especially waterfowl can spread several diseases transmissible to pigs).

• Vehicles: Staff , visitors, feed/pig delivery-, or collection of slaughter ready pigs. Dedicated parking spaces and drive areas should be demarcated, signposted and its use enforced! Wheelbaths and/or spraying of vehicle undercarriages can also be used at the main entrance. No delivery/collection truck should physically enter the area where pigs are kept. The practical challenges of feed storage and distribution will be different on every farm, but these should not be adapted for convenience while every delivery/collection truck is allowed to spread diseases from other farms and abbatoirs. Remember that even healthy porkers/ baconers can carry/temporarily shed disease agents that can infect younger pigs.

• Airborne diseases and Ventilation Management: Ideally houses should be sited far enough from each other so that faecal dust from older pigs (or other farms) cannot be blown into houses with younger pigs. In practical terms this means lumping similar ages together, taking prevailing/dominant wind direction into account.

• Waterborne diseases and water reticulation system associated health risks: The water reticulation system builds up its own, complex microflora over time, and this biofilm can act as residual populations of many disease agents. The water reticulation system should be cleaned (using a degreaser/ descaler) and then disinfected, at least twice a year at the beginning and end of summer. Some older farms will need to do it more often. These agents are often implicated in diarrhoea/enteritis in young pigs.

Create a barrier/buffer

• Time = "quarantine"; = separate new arrivals from the others, dedicate houses/sheds to those, do not mix old and young (applicable to gilts and older sows also!). As long as practically possible; ideally 2 weeks plus.

• Space/distance; see discussions above.

Effective immunization

• Correct vaccine choice; diagnostic procedures should be followed on all mortalities and coordinated with your Veterinary Consultant.

• Correct timing of vaccination; allow vaccines to stimulate protective responses before the major challenges occur. Make use of abbatoir lung lesion scoring and other organ evaluation techniques.

• Correct vaccination technique; train workers to understand the reasons behind what they are doing, vaccine handling, and injection techniques. Monitor the number of doses used against the expected volume used. Record this in your "Pharmacy Data Base" where you also record all antibiotic use and generally keep track of all medical stocks.

Efficient hygiene and disinfection

• Choice of disinfectant(s); Evaluate chemicals based on efficacy data against targeted index organisms, safety data, non-corrosion data, and then calculate the cost per working liter to make your final descision. A single compound will seldom be the disinfectant of choice for all applications.

• Correct application: concentration and contact time; automate the mixing/ dilution procedures to avoid human error. Monitor disinfectant use against expected volumes of concentrates used.

Biosecurity Plan (designed in close conjunction with your Veterinary Consultant)

• A written, dynamic document stipulating the "best practice’ standard operating procedures that will be followed on the particular pig farm

• HACCP: Identify the practical, critical control points

• Monitor these,

• Regular review and adjustment where necessary of plan/document.

Even when something does not work in practice all the time, it is still worthwhile because everything we do that will lower disease risks, count together. Compare biosecurity management practices to different strands forming a sieve/net, the more strands, the smaller the holes and fewer infectious agents/mechanisms of introduction (or any kind of risk that will endanger the security of your "ecosystem") will successfully enter your facility. However, the opposite is also true!