dr. peter davies - what pedv taught us about biosecurity?
DESCRIPTION
What PEDv Taught Us About Biosecurity? - Dr. Peter Davies, University of Minnesota, from the 2014 Allen D. Leman Swine Conference, September 15-16, 2014, St. Paul, Minnesota, USA. More presentations at http://www.swinecast.com/2014-leman-swine-conference-materialTRANSCRIPT
What has PEDv taught us about biosecurity?
Peter Davies BVSc, PhD
Department of Veterinary Population Medicine University of Minnesota, College of Veterinary Medicine, St. Paul, MN, USA
Bayesian Thinking• Thomas Bayes – theologian/mathematician• Conditional probability
• Bayesian statistics
Prior probability (belief/opinion)
New Information
Revised probability (belief/opinion)
Bayesian Thinking
What we know, think or believe
about biosecurity
PEDV experiences
What we now know, think or believe about
biosecurity
What is Biosecurity? (FAO/OIE/World Bank, 2008)
• Protection of health through avoidance of disease
• Implementation of measures that reduce the risk of the introduction and spread of disease agents
• Requires the adoption of a set of attitudes and behaviors by people to reduce risk in all activities
• Prevent introduction of disease to a farm— bio-exclusion or “external biosecurity”
• Prevent transmission within a farm
― biocontainment or “internal biosecurity”
Biosecurity Principles in Swine Production
Biosecurity: A science or an art?• Hard to research – use ‘principles’• What might happen?• What can happen?• What does happen, and how often?• Low risks borne widely = big problem
– Car accidents, Foodborne disease, Lightning strike– Pathogen introduction to a country/farm
• Difficult to ‘know’ sources of entry
Biosecurity: A science or an art?• Opinion >>> evidence• Small amount or research
– Contrived conditions– Lack of replication
• ‘Normal standards’– Cost effectiveness– Compromise– Compliance
Farm Processes
Waste
Garbage
Reclaim
GiltsBoarsSemen
Breeding Stock Commercial pigs
Water
Feed
People
Supplies
Equipment
Pests
Air
Farm Inputs and Outputs
Controlled access
National• Animals• Products• Inputs
– Vaccines– Feed ingredients
• Trade = risk
Farm• Animals• People• Inputs• Fomites, transport• Environment (air,..)
Successes: exclusion from herds/regions/countries
• Sarcoptic mange, lice• Brucellosis, Pseudorabies• ‘Exotic’ Diseases (e.g. FMD, hog cholera)• Atrophic rhinitis• APP• Swine dysentery?• TGE?
Less success• Struggles – high risk of recurrence
– PRRS– Influenza– Mycoplasma
• “Emerging” diseases– ASF– PEDv
What determines success• Characteristics of agent/disease
– Routes of exit and transmission– Host range and survival outside the hosts– Infectivity (ID50)
• Characteristics of the host– Immunity; infectious period
• Characteristics of the environment– Area density; Animal density; hygiene– Biosecurity measures and management
What we know about biosecurity • Important• Expensive• Can be annoying• Imperfect• Optimize cost vs. rate of failure
– Air filtration, transport biosecurity– Cost of outbreak (boar stud vs. breeding vs. WTF)– Law of diminishing returns
What we know about biosecurity • Need clearly described procedures• People need to know the procedures• Compliance is key
– Biosecurity culture– ‘Ownership’ and understanding the why
• Zero risk does not exist
What has PEDv made us ask about biosecurity?
• How ‘leaky’ is national biosecurity?– How many new viruses (1…x)
• Point source failure vs. systematic deficiencies?
• What was the source(s)/failure(s)?• When was the failure?• What needs to be changed?
What has PEDv taught us about biosecurity?
• ‘High’ standards (PRRS driven) did not prevent epidemic
• PEDv ≠TGEV– Current standards OK for TGE– High virus production, low infectivity– Totally naïve population– Immune response appears different
• Relative lack of knowledge
Agent Concentration
Structural characteristics
Strain characteristicsAggregation in matrix
Agent Concentration
Structural characteristics
Strain characteristicsAggregation in matrix
Environmental conditionsTemperature
Relative HumidityWater activity
pHOrganic matter
UV light exposure
Environmental conditionsTemperature
Relative HumidityWater activity
pHOrganic matter
UV light exposure
MatrixFecesWaterFeed
Fomites
MatrixFecesWaterFeed
Fomites
STABILITY OF THE AGENT OUTSIDE
THE HOST
Big questions• Industry on wheels – accepted risk!• Role of feed
– How important is/was it?– Is PEDv uniquely adapted to feedborne route?– Have we ignored feedborne transmission for
other pathogens?• Airborne transmission?• Precautionary vs. science based decisions
Bestpractices
Summary
• PEDv taught us nothing about biosecurity• It changed the equation nationally
– does the system have to change?• It changed the equation nationally
– Shift in the cost/benefit of biosecurity investment
• Refinement requires real knowledge