risk factors in poultry production systems€¦ · (denominator data and ascertainment bias) •...

Risk factors in poultry production systems

L. D. [email protected]

Risk of incursion

• The risk of incursion of H5N1 HPAI viruses (or other pathogens) into a farm is determined by:

- the number of ‘contacts’/links with the world outside the farm

- the probability of each of these ‘contacts’involving infected or contaminated material

Risk of virus incursion

• This depends on the level of infection in the area (hard to measure and varies over time) …

• And the measures taken to reduce the likelihood of infection on/in items that enter the farm (e.g. water treatment , change of clothes, etc)

Risk of virus incursion

• Each individual farm or flock has its own risk profile for introduction of pathogens and subsequent development of disease

• This is influenced by a number of factors, including the density of farms (density-dependent (airborne) and density-independent pathogens)

Biosecurity

• “All measures taken to prevent incursion and spread of disease/pathogens”

• “Biosecurity means taking steps to ensure good hygiene practices are in place so that the risk of a disease occurring or spreading is minimized” Defra UK

Farm biosecurity measures

• Location • Physical• Operational

• Disease can occur as a result of inattention to any of these

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• Industrial integrated system with high level biosecurity and birds/products marketed commercially (low risk, high impact)

Poultry production system 1

• Highly sophisticated biosecurity measures • Often international linkages (operating in

more than one country) • Strong political connections (trust)

• High level of inputs and outputs• Prepared to relocate to more isolated sites• High impact if outbreak occurs

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• Commercial non-integrated poultry production system; ‘moderate to high biosecurity’; birds and products marketed commercially

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• Commercial poultry production system; minimum or very low biosecurity; marketing via live bird markets


• Minimal investment in biosecurity measures• Sometimes due to lack of capital or lack of

ownership of facilities• Some develop from smaller flock• Opportunistic• Often linked to live poultry markets • Some production methods cannot be made

biosecure without totally changing the method of production (e.g. grazing ducks)

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• Village or back yard production(scavenging) - no biosecurity, informal marketing


• In some places limited links to formal market chain and in isolated communities very low risk (unless wild birds involved)

• Attempts to fence scavenging poultry make no sense to poultry owners

What has H5N1 HPAI taught us?

• Classifying all industrialised poultry farms together, without regard to the biosecurity measures implemented is unhelpful (provides no indication of the likelihood of disease outbreaks on individual farms)

• This simplistic approach has been adopted by many of those critical of ‘intensive production” and its purported role in H5N1 HPAI


• Most reports of H5N1 HPAI outbreaks in intensively reared poultry in Asia provide insufficient detail on the biosecurity measures practiced to assess whether disease occurred as a result of poor management or the level of infection around the farm overwhelmed otherwise ‘reasonable’ measures


• In some situations, on-farm biosecurity measures alone are not enough to prevent infection and disease (e.g. Hong Kong) –combination of improved biosecurity with vaccination

• Outbreaks may depend on a series of low probability events


• ‘Blame’ for Asian-lineage H5N1 HPAI outbreaks cannot be attributed to any one production system (but note role of domestic ducks and poorly regulated live poultry markets)

• Farms in all systems have been affected and played some role in the persistence and spread of this disease

• Although more cases of HPAI are generally found in system 3 flocks there is insufficient accurate data to allow comparisons of susceptibility of different farm types (denominator data and ascertainment bias)

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Risk analysis

• Done informally in establishing biosecurity measures

• Should be done more often for farms • Will highlight large gaps in knowledge

regarding the level of hazard to farms• Should follow standard steps • Qualitative, but can still measure certain

aspects especially the effects of interventions

Biocontainment

• Most farmers focus on preventing entry of pathogens and less about preventing onward spread

• Major issue in areas with high poultry farm density

• Role for government in regulation and enforcement

Enhancing farm biosecurity

• Market forces (& self interest)

• Regulation (and cost sharing for emergency disease)

• Communication/persuasion (get message right)

• Threat of litigation? (not yet but look at food safety in the US after E.coli O157)

• Like buying insurance

The future

• Loss of public tolerance for control through mass culling

• Pressure on areas with high concentrations of farms

• Pressure on system 3 (more contract growing?)

The future

• Greater enforcement/regulation• Use of complementary measures if

needed for ‘high risk’ production systems rather than their elimination

risk factors in poultry production systems€¦ · (denominator data and ascertainment bias) •...

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