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Comments to the FSIS/APHIS
meeting on the Harvard BSE risk analysis project
by
Michael Hansen, Ph.D.
Consumer Policy Institute, Consumers Union
September 28, 1998
Arlington, VA
Consumers Union* commends the USDA for commissioning an independent analysis of USDA's current measures to detect and prevent bovine spongiform encephalopathy (BSE) in the US meat supply. We also commend the agency for holding this public meeting to discuss the scope of the BSE risk analysis project.
Last month we sent a letter to the agency containing a series of scientific and policy questions which we believe the risk analysis should address (Silbergeld and Hansen, 1988). Since you have the letter, I would just like to mention four key points that we think the risk assessment should address.
First, the Federal Register notice for this meeting states that its purpose is to assess USDA measures to prevent BSE from entering the U.S. We ask the agency not to restrict their analysis to British-style BSE. Rather we think the study should address the risk from all TSEs, not just BSE. We note that a number of TSEs (scrapie in sheep, chronic wasting disease in mule deer and elk, and transmissible mink encephalopathy [TME]) are known to occur in the U.S. In addition to these known TSEs, we would urge that the risk assessment clearly look at the indirect evidence that suggests that an undiagnosed TSE occurs in US cattle. This evidence comes from studies of TME and has been laid out in a letter that we sent to FSIS last year (Hansen, 1997). We also urge that the analysis look at the indirect evidence, laid out in a letter to FDA last year, that a TSE may have occurred in pigs in the U.S. (see Hansen and Halloran, 1997).
Second, we would urge the project to look at the human epidemiology studies, particularly case control studies, which have connected eating of various meat products with increased risk of sporadic CJD. In the U.S., a couple of case reports have suggested that CJD may be related to consumption of wild animal (squirrel) brain (Kamin and Patten, 1984; Berger et al., 1997). In addition, two case control epidemiology studies in the U.S. have addressed whether there are any dietary risk factors for CJD. One looked at the risk associated with consumption of brain (Bobowick et al., 1973). The other found that 9 individual food items were statistically linked to increased risk of CJD. Of the 9 food items, 6 came from pigs (Davanipour et al., 1985). A case-control study of risk factors of CJD in Europe found a significantly increased risk of CJD associated with consumption of raw meat or brain; the same study also found an increase in risk of CJD with increasing consumption of pork (van Duijn et al., 1998). Finally, a case-control study of sporadic CJD in the United Kingdom found a significantly increased risk of CJD associated with consumption of beef, veal, venison and brains (National CJD Surveillance Unit, 1998).
Third, we would like the analysis to consider scientific evidence from the past two year that suggests that TSEs may be more problematical than we thought. More specifically, there is the work involving in-vitro conversion of the normal form of the prion protein (PrPc) to the abnormal, protease resistant form [PrPsc] associated with disease. These in-vitro studies have been shown to work well when investigating susceptibility to scrapie (Bossers et al., 1997). More recent work using this system showed that BSE and scrapie were capable of converting normal human prion protein to the abnormal form (Raymond et al., 1997). There is also the work published earlier this year that showed that scrapie infectivity could persist long term in brain and spleen tissue without causing the development of clinical symptoms (Race and Chesebro). The potential implications of the work were pointed out in an accompanying commentary on the paper: "Pigs and chickens that have been fed with cattle-derived bone and meat meal are thought to be safe to eat with respect to BSE, because these animals do not develop disease after oral exposure to bovine prions. But, to the best of our knowledge, bovine prions from BSE-exposed pigs and poultry have never been assayed using calves as 'indicator' animals" (Aguzzi and Weissmann, 1998: 764). We note that the feed rule FDA promulgated last year permits the feeding of bovine meat and bone meal (MBM) to pigs and the feeding of porcine MBM to cattle.
Fourth, it is frequently argued that TSEs are not in the food supply and do not pose a potential threat to human health because the incidence of CJD deaths has not risen over the years and is remarkably stable at about 1 in a million. We question that assumption. There is some evidence that the true incidence of CJD may be higher due to underreporting or misdiagnosis. CJD Voice is a support group for people that have had a case of CJD in their family or friends. As of July, 1998, there were 223 members of CJD Voice that were involved with CJD victims. A survey of these members revealed that of 99 cases reporting an initial diagnosis, only 8 were CJD. The most common initial diagnoses were stroke (18), depression (13), dementia (10), unknown (6), and Alzheimer's disease (5).
Further, a couple of studies suggest that CJD may be misdiagnosed as Alzheimer's disease or other senile dementia and that a small percentage of the Alzheimer's cases are actually CJD. A study at the University of Pittsburgh, in which autopsies were done on 54 demented patients diagnosed as having probable or possible Alzheimer's or some other dementia (but not CJD), found 3 cases (or 5.5%) of CJD among the 54 studied (Boller et al., 1989). A Yale study found that of 46 patients diagnosed with Alzheimer's , 6 (or 13%) were CJD at autopsy (Manuelidis and Manuelidis, 1989). Since there are over two million cases of Alzheimer's disease currently in the United States, if even a small percentage of them turned out to be CJD, there could be a hidden CJD epidemic. We urge that the risk assessment consider this information.
______
* Consumers Union is a nonprofit membership organization chartered
in 1936 under the laws of the State of New York to provide consumers with information,
education and counsel about goods, services, health, and personal finances;
and to initiate and cooperate with individual and group efforts to maintain
and enhance the quality of life for consumers. Consumers Union's income is derived
solely from the sale of Consumer Reports, its other publications and from noncommercial
contributions, grants and fees. In addition to reports on Consumers Union's
own product testing, Consumer Reports, with approximately 4.5 million paid circulation,
regularly carries articles on health, product safety, marketplace economics
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Consumers Union's publications carry no advertising and receive no commercial
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References
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Berger, J.R., Weisman, E. and B. Weisman. 1997. Creutzfeldt-Jakob disease and eating squirrel brains. The Lancet, 350(9078):
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Boller, F., Lopez, O.L. and J. Moossy. 1989. Diagnosis of dementia: Clinicopathologic correlations. Neurology, 39: 76-79.
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Kocisko, D.A., Priola, S.A., Raymond, G.J., Chesebro, B., Lansbury, Jr., P.T. and B. Caughey. 1995. Species specificity in the cell-free conversion of prion protein to protease-resistant forms: A model for the scrapie species barrier. Proceedings of the National Academy of Sciences, 92: 3923-3927.
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Race, R. and B. Chesebro. 1998. Scrapie infectivity found in resistant species. Nature, 392: 770.
Raymond, G.J., Hope, J., Kocisko, D.A., Priola, S.A., Raymond, L.D., Bossers, A., Ironside, J., Will, R.G., Chen, S.G., Petersen, R.B., Gambetti, P., Rubenstein, R., Smits, M.A., Lansbury Jr., P.T. and B. Caughey. 1997. Molecular assessment of the potential transmissibilities of BSE and scrapie to humans. Nature, 388: 285-288.
Silbergeld, M. and M. Hansen. 1998. Letter to Kaye Wachsmuth and Ruth Etzel (FSIS/USDA) dated August 7, 1998.
