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By Mojtaba Yegani, University of Alberta, Canada, and Gary D. Butcher, University of Florida, USA

There has been tremendous growth in the global poultry industry over the past decades. Some regions have reported a dramatic increase in the incidence of infectious disease outbreaks during this time of rapid expansion. However, in spite of difficult challenges facing the industry on a global level, poultry products (meat and eggs) still represent a major part of animal protein consumed by humans. Today’s consumers are generally more health-conscious and react strongly to perceived safety issues associated with the consumption of products of animal origin. Mad cow disease (BSE), avian influenza (AI) and salmonellosis are just a few examples of these contemporary concerns. Today, when the media tends to create hype rather than reporting the news, it is even more important to maintain a continuous vigilance to keep consumer confidence in poultry products.

Poultry health status

Maintaining excellent health of poultry flocks is the primary objective of any producer, since a healthy flock can be translated into a profitable flock. Despite all progress in prevention and control of infectious diseases, it is still difficult to keep a commercial poultry facility completely disease-free. Commercial poultry farms continue to be affected by the emergence of new or variant disease agents. Diseases are generally responsible for mortality, as well as reduced growth rate and egg production in poultry flocks, thereby resulting in reduced economic returns to producers. The emergence of new diseases and variants of existing diseases are becoming more common in the industry. Genetic changes in micro-organisms might have, in part, also contributed to this situation. Similarly, genetic changes in the birds might have also altered their susceptibility or resistance to diseases. Global trading and travelling have made it difficult to keep diseases to limited areas or regions.

Complex interactions

There are complex interactions among poultry, the environment, and disease agents. Factors directed at specific or non-specific immunity of the birds can affect their ability to resist disease if exposure to the agent occurs. Activities directed at the disease agents mainly influence the exposure of the birds to the agent. Environmental factors can also affect both the birds and the disease agent.

With the current tendency for regulatory agencies in many parts of the world to further limit the use of antibiotic growth promoters and therapeutic antibiotics, more effort must be directed at disease preventive strategies rather than the use of pharmacologic treatments. There are different sources or methods that can introduce diseases into a farm or spread infections within or between farms, including: human (employees, visitors); airborne transmission; carrier birds within a flock; birds in hospital/cull pen in a poultry house; birds recently obtained from an outside flock; forced-molted hens; eggs from infected breeder flocks; backyard, pet fowl, and wild birds; pet animals, rodents and insects; live-bird markets; contaminated feed and water, and; contaminated vaccines.

What happens next?

With the tendency for larger farms and with higher bird density, the above-mentioned methods of disease spread can contribute to dissemination of infectious agents, either directly or indirectly. There could be severe losses following a disease outbreak, or the emergence of a more pathogenic form of a given disease. Sub-optimal performance due to a disease can result in economic losses, although there are no exact estimates of losses associated with diseases. Specific factors such as virulence of the agent, immune status of the flock, previous exposure to immunosuppressive agents or conditions, housing design, stocking density, and environmental conditions are all variables that can influence the extent of losses following a disease outbreak.

Biosecurity an old concept

Biosecurity is a term frequently used in the poultry industry. Many people believe that biosecurity is only implementing a strict visitor control and farm cleaning programme. In reality, however, a comprehensive biosecurity programme goes beyond these and includes many other components. In any commercial poultry operation, flock health must be excellent in order to achieve maximum profitability. Health status can often be directly correlated with the comprehensiveness of the biosecurity programme implemented in an operation. It should also be noted that competence of the immune system of birds is of critical importance.

Biosecurity is the efficient use of common sense hygiene procedures in preventing the adverse effects of a disease. It can be defined as “a set of management practices that, when followed, reduce the potential for the introduction or spread of disease agents onto and among sites". In other words, biosecurity is an essential component of a disease control programme in the poultry industry. Some important considerations in designing a biosecurity programme are highlighted in Table 1. Clearly, a biosecurity plan must be adapted for each operation because each operation usually has its own unique situation. There is no standard formula applicable to all poultry farms.

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