NR ASCS
AU MacDiarmid,S.C.
TI Overview of Sourcing Considerations for Evaluating TSE Risks
QU Workshop on TSE Risks in Relation to Source Material, Processing, and End-Product Use. June 8-9, 1998, College Park, MD
IA http://www.life.umd.edu/jifsan/tse/program.htm
PT Workshop
AB
Although appropriate measures to protect humans from exposure to BSE had been introduced in the UK early in the epidemic, the recognition in 1996 that BSE had probably been transmitted to humans has led to the introduction in many countries of measures designed to reassure anxious consumers. Measures have been introduced or mooted to protect livestock and humans from exposure to BSE, the other recognised TSEs of livestock, and even hypothetical TSEs of livestock.
Not all the measures proposed or implemented are really appropriate to the risks being managed. In terms of costs of implementation, costs to industries and in terms of the actual risks, many measures appear excessive. Management measures should be in proportion to the risks being managed. This Workshop on TSE Risks in Relation to Source Materials, Processing and End-product Use is an opportunity to begin to formulate principles for evaluating the risks and the management measures which are appropriate and in proportion to those risks. Measures should be formulated on a case by case basis, depending on the tissues used, the country of origin and the intended end use of the product. Where certain tissues are excluded from use, the costs will include the consequences of their withdrawl.
VT
Thank you, Will. Good morning ladies and gentlemen. It is a privilege to be invited to come and speak to a gathering like this and to be one of the early speakers. My task is to provide an overview of sourcing considerations for evaluating TSE risks. The speakers later will cover aspects of the topic in more detail.
Measures to protect human and animals from exposure to BSE were introduced early on in the British BSE epidemic. However, with the recognition early in 1996, that humans had possibly contracted BSE, (new variant CJD), we saw the introduction, and proposed introduction, in many countries of measures which were designed to reassure anxious consumers. Measures were proposed to protect livestock and humans from the BSE and the other TSEs of livestock such as scrapie, and even hypothetical TSEs of livestock.
Now, I believe that not all the measures that have been proposed or have been implemented may necessarily be appropriate to the risks that are being managed. In terms of cost of implementation, costs incurred by regulatory agencies and costs to industries, many measures appear excessive in proportion to the actual risks to livestock and humans. I believe that risk management measures should in some way be proportional to the risks being managed. The risks, and particular appropriate management measures, should be determined through risk analysis.
Risk analysis is made up of three (3) components; hazard identification (what could go wrong?), risk assessment (How likely is it to go wrong and what would be the consequences?) and risk management. So, in the context of today's meeting, of what could go wrong is the exposure to BSE. However, many of the measures that have been or are being proposed appear to be designed to prevent exposure to scrapie and I will remind people that there has never been any demonstration of a link between scrapie and human disease. We have even been confronted with suggestions that there could be risks from exposure to chronic wasting disease of deer or even to other, hypothetical TSEs of livestock. So we've covered hazard identification and we now look at risk assessment. Now, where I come from, we look at risk assessment in three (3) components. The first is called the release assessment, (this is the terminology inherited from environmental risk analysis). It is the way I look at it at home, because in my country our livestock are free from BSE, scrapie and chronic wasting disease, and so, in our context, release means the passage across our borders of the causative agent for one of these diseases. How would that happen and how likely is it to happen? Perhaps more important in the today's context is the second component, the exposure assessment. That is, the exposure of humans or livestock to one of these TSE agents. How would it happen and how likely is it to happen? Just because you can imagine something happening doesn't mean that it's very likely to happen. And the third component is the consequence assessment, and I guess that, in terms of exposure of humans, it's an extremely serious consequence. So, continuing to look at the risk assessment, we need to take into account animal considerations, such as the species of animal from which we are considering sourcing our raw materials. Clearly one is going to pay different attention depending on whether we're sourcing from cattle or sheep or chickens or whatever. Within some species, we may want to pay attention to issues like the genotype. We know, that in sheep the manifestation of scrapie is significantly influenced by the genotype. There doesn't appear to be a similar basis in cattle. The age at slaughter is another very important consideration as the TSEs are diseases with a very long incubation period and infectivity appears in different tissues as the disease evolves. So, the risk from the materials, any given materials is going to be different depending on the age at slaughter. Obviously one also considers an issue like the health of the animal at the time it was slaughtered. If the animal has an advanced neurological disease when you slaughter it, it might present a different risk than one that hasn't. And naturally enough, the particular tissues that we harvest. What we're talking about, in the risk assessment, is the origin of the animals and we're talking in two (2) tiers. The first one (1) is where we're talking in terms of country of origin, because different countries differ in the risks that you're going to attribute to raw materials harvested there. Clearly, the risk from material harvested from cattle in the United Kingdom would be different from the risk from material harvested from cattle, say, in Australia, a country which has no TSEs. In looking at the country of origin, however, you need to take into consideration things like surveillance programs, importation policies, husbandry practices. And when a country says that it's free of BSE or something, is it free because nobody's ever looked, or is it free because their surveillance system and other policies lead one to that conclusion?
Exactly the same type of things apply within a country when one is looking at the herds or flocks of origin. One looks at the herd or the flock surveillance or accreditation programs for assurances that can be given that this herd or flock is indeed free from one of these diseases of which we're concerned. One also needs to look in the herd or the flock at introduction policies, just the same as on the national level, the importation policies. Are measures in place to assure that the diseases of concern are not introduced into that herd or flock just as the country must have in place measures to ensure that the disease is not introduced? And finally one considers the herd or flock husbandry practices. What is fed to the animals? A country like my country where we have virtually never fed concentrate feed to our cattle or sheep, because we have more grass than we need, presents a different risk to the husbandry system where concentrate feed is used in large volumes.
Third, the next component we need to consider are the risk management measures. Now, risk management in my opinion, that is, the safeguards that are imposed, should be in some way in proportion to the risks being managed. As a regulatory agency, we do not have an unlimited funding base with which to protect people and livestock from a wide range of risks. One needs to ask oneself what is it that causes the greatest risk to the consumer. Is it the TSEs to which they might be exposed? Or do other risks from more conventional sort of agents, such as Salmonella, E.coli or whatever, are those perhaps where the greatest risks to the consumer lie? And as the funding is not unlimited, money spent in one area is money not spent in another area. So, it's important that the measures be proportional to the risks being managed. And in considering the costs of these measures, one has to look at the cost of excluding particular sources. One has to look at the cost of imposing measures, if you're going to test every animal at slaughter. That is, money spent which may be better used elsewhere. And then there's the issue of the so called spontaneous TSE in cattle. Nobody's actually ever found it yet, but some people fret about it.
Part of risk management is the surveillance programs applied nationally or at a herd or flock level. And you need to consider, surveillance for what? Are you talking about surveillance in the case of cattle for BSE, or this hypothetical TSE of cattle? Because you need to consider what is the purpose of surveillance. Surveillance for what end? Are you asking for assurances about the population? Or are you asking for assurances about individuals? Assurances about individuals are going to be a lot more costly than the assurances about populations. And what is the sensitivity of this surveillance? What is the sensitivity you're demanding from this surveillance? I will just reiterate that in my opinion, measures imposed should be proportional to the risks that are being managed. In looking at risk management you will need to take into account the control policies that are applied. The control policies have two (2) aspects. First, the dealing of the cases, what happens with a case? And really this is the smallest, because by the time you discovered you have the case, just about everywhere you discover it, you've confirmed that one is dead. And then you dispose of it. More important are the prevention of exposure, the livestock to exposure, feeding practices and that sort of thing. Now in considering risk management, one should not in my opinion get paralyzed to the point of indecision over some of the uncertainties. Because each has the risk of release, that is the agent entering the environment of which your hosts are present. Even if the risk of release or the risk of exposure are uncertain it may be possible to estimate with some degree of confidence the effect of different risk management strategies. And one also needs to take into account notions like the ratio of risk to benefits when considering, not just with this product, but the use of any of the products. The almost global acceptance of the need to exclude meat and bone meal from the ruminant rations has not been adopted everywhere. There are countries such as those in Southern Africa where protein is such a scarce resource that the cost of excluding meat and bone meal from livestock rations may be way out of proportion to whatever risk might be managed by that. So finally, this workshop, I see it as an opportunity to begin to formulate some principles for evaluating the risks and the management measures which are appropriate and proportionate to the risks that are identified. Measures should be formulated, I believe, on a case by case basis depending on the tissues which are to be used, the country of origin and the intended end use of the product. And when certain tissues are excluded from use, the cost will include the consequences of their withdrawal. Thank you ladies and gentlemen.
IN Der leitende Beamte des neuseeländischen Landwirtschaftsministeriums Stuart C. MacDiarmid betont, dass man nicht zu viel Geld für seiner Meinung nach übertriebene Maßnahmen gegen nicht endgültig bewiesene Gefahren tierischer TSEs für die menschliche Gesundheit verschwenden solle. Ein zynischer Verharmloser!
ZR 0
AD Stuart C. MacDiarmid, National Manager, Agriculture Security Regulatory Authority, Ministry of Agriculture and Forestry, PO Box 2526, Wellington, New Zealand
SP englisch