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