Download Virus inactivation risk assessment: work in progress

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
hazard

Virus: PEDV / all porcine viruses
 Describing

and characterization of the
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
Blood from clinically healthy animals
(virus dilution)
Anti-coagulants
centrifugation
Possibilities for chemical / physical treatment
filtration
Spray - drying
standardisation
storage
Heated to 80°C (thermal inactivation)
Possibilities for chemical / physical treatment
Inactivation during storage
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 Dose
Max 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 nonzero 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




APC


Funded by National Pork Board
Risk assessment ingredients of porcine origin
Started in April
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