Human TSEs and blood transfusionEfforts and needs for global control of BSE and vCJD
Maura N. Ricketts MD MHSc FRCPC
WHO/CDS/CSR/EPH
Bovine Spongiform Encephalopathy (BSE)
Feline Spongiform Encephalopathy (FSE)
Animal TSEs
Scrapie no considered to be zoonotic
TME - some consideration that linked to BSE, but not widespread and not a risk where countries don’t use carcasses in feed; not widespread
FSE, TE of ezoo animals are not being formally surveyed despite being BSE
Focus on BSE
BSE and vCJD - same agent
BSE epidemic in cattle was caused by BSE-contaminated MBM
Principle source of exposure for humans is food
human to human is a possible secondary route
No test to detect agent in food or living asymptomatic animals
begin by laying the groundwork of things that are considered to be factual, or are assumed principles during the presentation.
Will not discuss prions or any theories about prion diseases
January 2002
prohibited
Starting point of the problem is an epidemic of BSE which occurred in the UK, beginning in the mid ‘80’s and continuing today
Note that the ban of live British cattle exports, an activity designed to prevent the spread of an animal disease, began in 1989; note that MBM could still be exported.
Note that the ban on British beef began only in 1996, after the deaths of the first four cases of vCJD were published.
Cross marks Steven Churchill’s death
January 2002
UK Rates by region - demonstrate decline due to intervention measure.
NB - highest rate of BSE is in Guernsey (island) but only few hundred cases. Highest number in Great Britain, rate as high as 4,400, now 288 per million
point out that GB rates are in yellow
January 2002
NB: Guernsey removed
Relevant to look at the rates of BSE over and above the simple numbers. The highest rate of BSE remains in UK.
NB Guernsey is removed because the rate is so high. The three seen are UK and Ireland.
Look at other countries in separate graph
January 2002
OIE Data, 21 December 2000
N~182,000
United Kingdom
This graph compares BSE in the UK and EU. The size of the epidemics is very different - the scale for UK is in 10thousands and for EC in hundreds. Regardless, the efficacy of interventions in the UK is apparent.
January 2002
BSE Reports by Year
OIE, 3 January 2002
Starting point of the problem is an epidemic of BSE which occurred in the UK, beginning in the mid ‘80’s and continuing today
Note that the ban of live British cattle exports, an activity designed to prevent the spread of an animal disease, began in 1989; note that MBM could still be exported.
Note that the ban on British beef began only in 1996, after the deaths of the first four cases of vCJD were published.
Cross marks Steven Churchill’s death
January 2002
by Year and Country
Portugal
Ireland
France
Switzerland
Belgium
Data shows only countries with more than 10 cases. Year 2001 is incomplete reporting year so isn’t shown
Total number of cases outside of UK as of June 30 2001 is 2,303 (180,937 in UK, therefore about 1% of all cases from outside the UK)
Yellow - Portugal, 605
Pink - France, 344
Blue - Switzerland, 391
January 2002
Examine incidence rates
January 2002
WHO/CSR/APH
Impact of Active Surveillance: BSE reports in countries previously reporting no cases
Austria
WHO/CSR/APH
Impact of Active Surveillance: BSE reports in Countries previously reporting no cases
OIE Data, 30 June 2001
Spain
Italy
Germany
Since year 2000, first reports of BSE from 7 new countries
Czech republic - 5
Germany - 125
Greece - 1
Italy - 32
Japan - 1
Slovakia - 1
Spain - 69
As of June 30 2001, total 2303 reports of BSE outside of UK. In this group, total 235 (approximately 10%)
January 2002
Confirmed BSE cases (deaths)
Estimated 903,000 cattle infected from 1974-1995 assuming average incubation period of 4-6 years
most cattle are killed at 2 years of age, hence it is feared that 446,000 infected animals entered the human food chain before control measures introduced in November 1989 and a further 283,000 between Dec 1989 and Dec 1995
in UK, BSE affected 59% of dairy herds, 15% of beef suckler herds and 34% of herds with adult breeding cattle.
EU GBR document identifies the following risk periods
live cattle - 1988-1993, the prevalence of BSE in cattle is assumed to have been around 5% i.e. 1 in 20 animals
MBM - 1986-1990, peak in 1989 when SBO were excluded from the food chain but included in to rendering and feed production
January 2002
UK Customs & Excise Data
To find out whether there was an international risk, we reviewed the Customs and Excise data provided to us by the UK (similar data for other EU countries was not available) for exports of MBM, offals, meat, meat preparations and live bovines. We were impressed by the extent of global movement of the products.
We mapped this information using the SSC GBR as a model
January 2002
No data
0 - < 5
5 - < 10
10 - < 20
20 - < 100
100 - < 1.000
1.000 - < 10.000
Pure Bred AND Non Pure Bred
No data
0 - < 5
5 - < 10
10 - < 20
20 - < 100
100 - < 1.000
1.000 - < 10.000
Total Export of Bovine Offal and Meat preparations 1986 - 1990
No data
0 - < 5
5 - < 10
10 - < 20
20 - < 100
100 - < 1.000
1.000 - < 10.000
Pure-Bred and Non Pure-Bred
1978-1997
January 2002
1980 - 1988
No data
0 - < 5
5 - < 10
10 - < 20
20 - < 100
100 - < 1.000
1.000 - < 10.000
1980 - 1988
No data
0 - < 5
5 - < 10
10 - < 20
20 - < 100
100 - < 1.000
1.000 - < 10.000
1978 - 1998
No data
0 - < 5
5 - < 10
10 - < 20
20 - < 100
100 - < 1.000
1.000 - < 10.000
Does not include exports from other countries with BSE
Export and Import records may not tally
Re-packaging and onward sales obscure the origin of trade goods
Illegal or uncontrolled movements not reported
Doesn’t describe how the imports were used
January 2002
Scientific Steering Committee
EC review of the risk of BSE being present in a country
describes the risks of introduction of BSE and recycling
makes estimates of the risk levels of imported materials
requires information about internal risks
EU GBR document identifies the following risk periods
live cattle - 1988-1993, the prevalence of BSE in cattle is assumed to have been around 5% i.e. 1 in 20 animals
MBM - 1986-1990, peak in 1989 when SBO were excluded from the food chain but included in to rendering and feed production
January 2002
No data
Category I
Category II
Category III
Category IV
WHO/CSR/APH
WHO Consultation on Public Health and Animal TSEs: Epidemiology, Risk and Research Requirements
1-3 December 1999
“Eradication of BSE must remain the principle public health objective of national and international animal health control authorities”
Www.who.int/emc/diseases/diseases/bse/index.html
Global Dimension of BSE
Mediterranean/North African, IF small ruminants are a problem
What is safe to eat?
WHO - skeletal muscle meat and milk/milk products are safe to eat
Context - no tissue from an animal with BSE or suspected of BSE should be included in any food chain, human or animal….this implies adequate surveillance and implemented methods to ensure removal of sick animals from the food chain i.e. a BSE control program
What should be done to evaluate existing risk within any country’s boundaries?
What was imported?
How was it used? … bovine feed is the biggest problem; consideration of non-bovine animal feed issues; human exposures through food can be evaluated
Is there any rendering (within or without country boundaries)? … recycling opportunities should place the country on high alert
What should be done to prevent further global exposure?
National control programs including …. animal feed regulations, appropriate slaughter methods, handling of SRMs and adequate surveillance
international trade on animal feed must be reviewed
appropriate trade barriers on some human foods
January 2002
Consider illegal importation
How was it used?
Is there a rendering industry?
Export materials to other countries for rendering?
Global Seeding of BSE
Any potentially infected material imported?
Regarding BSE, concerned about materials which could be used in animal feed, including MBM and offals
Human foods of concern are mechanically recovered meat (meat preparations), offals and anything potentially contaminated by nervous tissue
How was it used?
It is not impossible that if fed to chickens and pigs,that this is a ‘safe’ route of disposal of these materials
this may not be true and there are many concerns expressed about the agent being passed through animals which don’t themselves become ill, but still expose humans
non-bovine animals may become part of rendering industries and may recycle the agent. In addition, they may contaminate the environment with their wastes.
Keep in mind that if feeding non-bovine animals with these materials is a safe way to use the materials, this solution may be better than having the materials stored in sheds where wild animals may have access, where water table and environment may be contaminated, where human exposure continues for the caretakers.
Must not loose track of problems arising if intended use is non-bovine animals, but cross-contamination occurs at factories, plants or on farm. This proved to be a major contributor to difficulties in eliminating BSE in the UK.
Rendering
this is a crucial point in terms of whether or not the BSE agent will be recycled.
Some countries don’t have rendering industries, but may trade the animal left-overs after slaughter into countries with rendering.
January 2002
Public Health - Exposure Assessment
called for pathway analysis
called for standardized international approach to identify whether food is safe to export or not
What is safe to eat?
WHO - skeletal muscle meat and milk/milk products are safe to eat
Context - no tissue from an animal with BSE or suspected of BSE should be included in any food chain, human or animal….this implies adequate surveillance and implemented methods to ensure removal of sick animals from the food chain i.e. a BSE control program
What should be done to evaluate existing risk within any country’s boundaries?
What was imported?
How was it used? … bovine feed is the biggest problem; consideration of non-bovine animal feed issues; human exposures through food can be evaluated
Is there any rendering (within or without country boundaries)? … recycling opportunities should place the country on high alert
What should be done to prevent further global exposure?
National control programs including …. animal feed regulations, appropriate slaughter methods, handling of SRMs and adequate surveillance
international trade on animal feed must be reviewed
appropriate trade barriers on some human foods
January 2002
risk that high risk materials are consumed by human populations
January 2002
Risk from external exposures i.e. importation of high risk materials
SRMs, MRM
NOT HIGH RISK - milk and milk products, gelatin prepared from hides and skins; WHO - skeletal muscle meat
pharmaceuticals, biologicals, blood not fully evaluated
January 2002
Hazard Identification
brain, eyes (retina), trigeminal ganglia, spinal cord, DRG, distal ileum
removals depend upon risk level
animals subject to measures depend upon risk
What is safe to eat?
WHO - skeletal muscle meat and milk/milk products are safe to eat
Context - no tissue from an animal with BSE or suspected of BSE should be included in any food chain, human or animal….this implies adequate surveillance and implemented methods to ensure removal of sick animals from the food chain i.e. a BSE control program
What should be done to evaluate existing risk within any country’s boundaries?
What was imported?
How was it used? … bovine feed is the biggest problem; consideration of non-bovine animal feed issues; human exposures through food can be evaluated
Is there any rendering (within or without country boundaries)? … recycling opportunities should place the country on high alert
What should be done to prevent further global exposure?
National control programs including …. animal feed regulations, appropriate slaughter methods, handling of SRMs and adequate surveillance
international trade on animal feed must be reviewed
appropriate trade barriers on some human foods
January 2002
BSE in Cattle
requested OIE to secure more risk assessments
requested OIE to use methods like GBR to assess risk level
i.e. risk based, not rate based
What is safe to eat?
WHO - skeletal muscle meat and milk/milk products are safe to eat
Context - no tissue from an animal with BSE or suspected of BSE should be included in any food chain, human or animal….this implies adequate surveillance and implemented methods to ensure removal of sick animals from the food chain i.e. a BSE control program
What should be done to evaluate existing risk within any country’s boundaries?
What was imported?
How was it used? … bovine feed is the biggest problem; consideration of non-bovine animal feed issues; human exposures through food can be evaluated
Is there any rendering (within or without country boundaries)? … recycling opportunities should place the country on high alert
What should be done to prevent further global exposure?
National control programs including …. animal feed regulations, appropriate slaughter methods, handling of SRMs and adequate surveillance
international trade on animal feed must be reviewed
appropriate trade barriers on some human foods
January 2002
We don’t know
EC is conducting GBR assessments of countries requesting assessments
OIE will review voluntary applications to determine if countries are in compliance with the OIE Code on Animal Health to be considered BSE-free
Risk Assessments requested of all OIE member countries by International Committee of the OIE
Surveillance systems to be established
Harm from BSE extends beyond human deaths and includes profound economic impact
It is worrisome, but we must acknowledge that the potential exposure to BSE is wide-spread
January 2002
Standard surveillance methods established
Animal - OIE and EC
Buenos Aires, Bangkok, Beijing, Bratislava, Cairo, Dakar
EC funded surveillance in NIS countries
WHO (human)TSE Collaborating Centres
What is appropriate to do?
Harm from BSE extends beyond human deaths and includes profound economic impact
Potential exposure to BSE is wide-spread
January 2002
http://www.who.int/emc/diseases/bse/
/meeting.htm
rickettsm@who.ch
Switzerland
Web site has connections to OIE and FAO, web site addresses for interesting sites, information about upcoming meetings, latest documents
January 2002
Risk Management Strategies
commensurate with risk
What is safe to eat?
WHO - skeletal muscle meat and milk/milk products are safe to eat
Context - no tissue from an animal with BSE or suspected of BSE should be included in any food chain, human or animal….this implies adequate surveillance and implemented methods to ensure removal of sick animals from the food chain i.e. a BSE control program
What should be done to evaluate existing risk within any country’s boundaries?
What was imported?
How was it used? … bovine feed is the biggest problem; consideration of non-bovine animal feed issues; human exposures through food can be evaluated
Is there any rendering (within or without country boundaries)? … recycling opportunities should place the country on high alert
What should be done to prevent further global exposure?
National control programs including …. animal feed regulations, appropriate slaughter methods, handling of SRMs and adequate surveillance
international trade on animal feed must be reviewed
appropriate trade barriers on some human foods
January 2002
Risk Management / MBM
MBM of ruminant origin must not be fed to ruminants
Where MBM is fed to other species
ensure no X-contamination
if cannot, don’t use any MBM in ruminants and don’t trade
MBM of ruminant origin must not be fed to ruminants.
In countries where ruminant MBM is fed to other food animal species, all possible measures must be in place to ensure avoidance of cross contamination of ruminant rations with feed for non-ruminant species (e.g. by using species-dedicated meat and bone meal production premises and/or feed production premises dedicated to ruminants and non-ruminants). Where such avoidance cannot be guaranteed, MBM from any species should not be fed to ruminants. In order to assure compliance, it may also be necessary to ban all mammalian protein-based animal feed from ruminant feeds or even from all farm-animal feeds. If cross contamination cannot be avoided then countries should not trade in these materials.
January 2002
Risk Management / MBM
international monitoring of feed bans
better QA of animal feed
If a country has identified BSE or, on the basis of a risk assessment, a BSE risk, then MBM for use in non-ruminants should be prepared from non-SRM material by the method prescribed in the OIE Code Article 3.6.3.1, or by a method that achieves equivalent or better inactivation.
Guarantees as to the quality, condition of production, the ingredients’ source and the composition of MBM must be a part of international risk management, to prevent the introduction or spread of BSE infectivity. International monitoring of compliance with the feed bans needs further development, including reliable certification programmes and screening tests to guarantee the absence of BSE infectivity in ruminant feed stuffs traded internationally. Emphasis must be placed on the development of rapid and reliable tests for the detection of ruminant protein in animal feeds.
January 2002
Risk Management / SRM
SRM ban extent depends upon risk
This Consultation has not provided reason to modify the basic list of SRMs as identified earlier in the section Risk Assessment for vCJD and BSE: Hazard Identification.
Issues such as slaughter-methods, cross-contamination during and after slaughter, and difficulties in the identification of specific tissues or organs under slaughterhouse conditions should be taken into account when determining if products are truly free of known sources of infectivity. For this reason, risk management options may include the identification and removal of entire bovine heads, as opposed to simply attempting to remove brain and eyes, or may include the prohibition of the harvesting of all mechanically-recovered meat (MRM), rather than just the elimination of MRM from the vertebral column.
Whenever the possibility that slaughtered animals may be infected with BSE cannot be excluded, all tissues with confirmed capacity to carry BSE infectivity should be removed and destroyed i.e. an SRM ban. Where this risk is higher, those tissues that under certain conditions are suspected to carry infectivity should also be considered for removal and destruction. If the risk is high, all additional possible precautions should be taken, such as a prohibition on cattle over a certain age from entering food or feed chains. The Consultation recommends that WHO, FAO and OIE review this approach specifically in relation to public health issues. Finally, consideration may be given to applying an SRM ban separately for human food and for animal feed.
January 2002
Animals with Confirmed or Suspected BSE
all suspects destroyed
discussed herd slaughter
Clinically confirmed cases in bovines and any progeny born in the last two years to female cases should be completely destroyed.
Given the limitations of the current knowledge concerning human infective dose and concerning the pathways for human exposure to infected tissues, the Consultation underlines that, as a precaution, all animals suspected of being infected with BSE should be destroyed.
Where a case has been confirmed, cohort animals i.e. animals exposed to the same risk should be destroyed. For this purpose adequate, individual animal identification and records of movement of cattle must be in place. Under some circumstances, consideration may be given to more extended slaughter by some authorities, even though no evidence for horizontal transmission exists. This action may be considered for social, political, economic or trading reasons and should be judged on a case by case basis.
The OIE Code article 2.3.13.4 paragraph 2b sub paragraph iii provides the following definition, 'all cattle either born in the same herd as, and within 12 months of the birth of, the affected cattle or reared together with the affected cattle during the first year of their life, and, in both situations, which may have consumed the same potentially contaminated feed as that which the affected cattle consumed during the first year of their life'
January 2002
Surveillance
…or risk failure
Surveillance data is fundamental for the safe trade of animals and animal products. Ongoing surveillance data provides an indicator of the effectiveness of risk management measures and monitors the effect of any changes in the overall BSE risk of a region, country or zone. Surveillance strategies should be commensurate with the BSE risk, but surveillance should include both active and passive components, as outlined in to Appendix 3.8.3 of the OIE Code, using methods described in the OIE Manual of Standards for Diagnostic Tests and Vaccines.
Countries should strongly consider, on the basis of the risk assessment, the use of appropriate tests on target populations, conducted sufficiently frequently and on a large enough number of animals to provide the necessary confidence that any risks are identified. Contingency planning for action following the identification of the first case of BSE in a country previously without reported cases should be established.
Compliance - Experience in countries with BSE has demonstrated that failure of implementation of adequate measures can lead directly to the failure of BSE control programs. Implementation of the chosen risk management options must be strictly enforced to protect global health and trade. Efforts by authorities must be directed at ensuring full compliance. Governments must pay particular attention to ensuring all risk reduction measures are actively established, implemented, enforced and audited. In particular, attention should be paid to the prevention of fraud.
January 2002
BSE in sheep
maybe a problem
where exposure to BSE has occurred, minimize exposure to humans
January 2002
Other Ruminants
include in feed bans
Other farmed animals
pigs and poultry
ostriches
horses
January 2002
Fur bearing mammals
Fish
Passage of infectivity
infectivity passes through gut
do not use digestive contents and faecal material from animals fed with MBM as a feed ingredient for animal feed
0
20
40
60
80
100
120
140
160
180
1991199219931994199519961997199819992000
1999
2000
2001
0
50
100
150
200
250
0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
400,000
19821984198619881990199219941996
0
10,000
20,000
30,000
40,000
50,000
60,000
198919901991199219931994199519961997199819992000
Ireland