Framework for a microbiological risk assessment to assess virus safety of blood products for feed

Dr Lourens Heres

Question How can virus safety of blood plasma be

quantified? What are the critical processes to assure

virus safety and which steps are insufficiently quantified?

Many examples of risk assessments Milk powder and Foot-and-Mouth-

Disease No reports of disease outbreaks pasteurisations

BSE: MBM, Fat, gelatine, waste water, etc… Different steps – exclusion SRM critical Severe heat inactivation

Risk of introduction animal diseases

Risk assessment elements Identification and characterization of the

hazard Virus: PEDV / all porcine viruses

Describing the pathways Exposure assessment

Processes (dilution, inactivation, etc.) consumption

Dose-respons assessment

Pig viruses posing a risk for porcine products in feed Endemic virusses

PRRSV PCV2 PPV Influenza Hepatitis E PEDV Parvo-virus …

Epidemic Virusses – OIE listed Classical Swine

Fever (CSF) Foot and Mouth

Disease (FMD) African Swine Fever Swine Vesicular

Disease (SVD) Aujesky‘s disease

PEDV Coronavirusses

Non-stable virus Easily inactivated

Virus in blood through leakage through enterocites in intestine, or faecal contamination during blood collection

Infectivity in blood not (yet) shown Infectivity of spay dried plasma not shown,

and due to spray drying and storage unlikely.

Collection of blood

Anti-coagulants

centrifugation

filtration

Spray - drying

standardisation

storage

Blood from clinically healthy animals(virus dilution)

Heated to 80°C (thermal inactivation)

Possibilities for chemical / physical treatment

Inactivation during storage

Possibilities for chemical / physical treatment

Risk assessment: critical Virus control along the chain

killed animal: no more multiplication Log-reduction steps

One or some infected animals in batch with multiple animals (pooling effect)

Heat and chemical treatments Drying (heat treatment) Storage

Other reduction with: splitting plasma and cells,…. Exposure

Several grams of the product are consumed during different days

Single hit

Infectivity – Infectious DoseMax infectivity level infected animals

Virus load/ml blood: PCV2 106 DNA FMDV 105,5 TCID50

PRRSV 103-4 TCID50

Infectious Dose in susceptible animals(all animals infected with:)

PCV2 ~104-5 TCID50 ~103,5 TCID50 FMDV

(intranasal, depending on strain)

ID50 PRRSV ~105,5 TCID50

Where could a quantitative risk assessment help

advantages Generic approach Understanding the

principles Structured

approach

challenges Unknown

parameters Uncertainty Variability Overestimation of

risk

Limitations for virus QMRA The outcome will never be a zero risk. Data from publications

PCR positive or culture infectious dose or animal infectious dose

Power of the experiment: numbers tested: plates, wells, or animals inoculated Amount of virus added in inactivation tests Detection limit of diagnostic tests

uncertainty Lab-condition versus Field-conditions

Spray driers Number of animals

Safe: to overcome the non-zero risk outcomes Risk assessment on animal diseases

shows that under the current control measures The probility of introduction

of CSF in The Netherlands 1 per 16 years of FMDV in the US 1 per 240 years Of FMDV in Spain 1 per 40 years

Risk assessments University of Minnesota

Funded by National Pork Board Risk assessment ingredients of porcine origin Started in April

APC Many studies, see summary next presentation J. Polo

Sonac With NIZO and Wageningen-UR Validation of virus safety

Different processes Different model viruses

Thank you for your attention