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by
Michael Hansen, Ph.D.
Consumer Policy Institute/Consumers Union
The U.S. Food and Drug Administration (FDA) has been considering for the past year what steps to take to prevent a mad cow epidemic like that in the United Kingdom (UK) from occurring in the U.S. The UK epidemic, which has killed more than 167,000 cows, and which has recently been linked to 17 human cases of a new form of Creutzfeldt-Jakob disease (CJD), is believed to have spread through contaminated animal feed.
FDA's decision, like others it must make in the public health area, requires the agency to make judgments based on incomplete scientific evidence. In this case, because of the extraordinarily serious consequences of a bad call, we believe FDA should err heavily on the side of safety. So far, it has not.
Mad cow disease, also known as bovine spongiform encephalopathy (BSE), belongs to a group of degenerative diseases called transmissible spongiform encephalopathies (TSEs), which affect the central nervous system, particularly the brain. Both humans and animals can get TSEs by eating infected tissues. Susceptibility may have a genetic basis.
The technical name comes from the fact that the brains of infected animals usually develop spongy looking holes filled with tangled amyloid protein fibrils. TSEs have long incubation periods and are invariably fatal. The infectious agent is resistant to deactivation.
On June 5, FDA published a final rule which imposes a partial ban on feeding rendered mammal remains back to ruminants (cud-chewing animals). However, the rule exempts swine, horses, blood, gelatin, and milk from the feed ban. Under the rule, rendered remains of pigs and horses could still be fed to cows and sheep, and vice-versa. In our view, the rule is an important step forward. Nevertheless, the rule still leaves the door open to spread of a TSE among domestic animals in the U.S.
The UK has prohibited feeding meat and bone meal (MBM) from any mammal to all food animals. The European Union, with the exception of Denmark, has banned use of all mammalian MBM in any ruminant feed.
FDA exempted swine because no "naturally occurring" TSE has yet been positively identified in pigs under natural conditions. However, this could just mean that the government has not looked hard enough. In a British experiment, a pig injected with brain material from a BSE cow contracted a TSE.
Most commercial pigs are slaughtered at the age of six months, long before the pigs would be expected to exhibit any signs of the disease. The government does not monitor any swine brains for evidence of TSEs. Scientific evidence from the US suggests that swine may actually already be infected with a TSE. Hogs in a 1979-80 USDA study at a packing plant in upstate New York showed many of the same behaviors found in BSE animals. USDA recently re-reviewed this study, and Dr. William Hadlow, one of the foremost TSE pathologists in the world, examined slides from one animal's brain.
Dr. Hadlow concluded that it was suggestive of a TSE. However, FDA stated that salt toxicity/water deprivation can produce similar clinical symptoms and brain lesions. But if a world-renowned TSE pathologist can't tell the difference between TSE-suggestive material and salt toxicity/water deprivation, then who can?
In addition, two small case-control epidemiological studies of some US victims of CJD, a human TSE, have found suggestive links to pigs. A 1985 study found that consumption of six pork products (smoked pork, roast pork, pork chops, ham, scrapple and hot dogs) increased the risk of CJD compared to a control group. The other study, from 1973, found that one third of the CJD patients ate brains, much higher than the US population overall. The patients also had a greater preference for hog brains compared to controls.
Perhaps the most egregious problem with the FDA rules is that they would permit known TSE-positive material to be used in pet food, pig, chicken and fish feed--FDA only requires that it is labeled "Do not feed to cattle and other ruminants." Thus, carcasses of scrapie-infected sheep and TSE-infected deer could legally be sent to the renderer and converted into pet and pig rations.
We frankly are astounded that the FDA would permit TSE-positive material to be used for any purpose. The decision flies in the face of recommendations from World Health Organization's International Consultation on TSEs and Public Health issues held last year. WHO urged that "No part or product of any animal which has shown signs of a TSE should enter any food chain (human or animal)."
The decision could cause trade problems for the US. Since FDA will now permit domestic companies to sell TSE-positive material as feed for pigs, poultry and pets, foreign companies must also be allowed the same privilege, according to GATT rules. Thus, the UK could decide to ship BSE-contaminated MBM to the US. If the US tried to stop such material (USDA has banned import of MBM from UK), the UK could bring a case before the World Trade Organization. Furthermore, EU countries could decide to ban importation of US meat because our feed laws are not as protective as theirs.
In addition to allowing TSE-positive material in non-ruminant animal feeds, the FDA rule also permits such materials in fertilizer and cosmetic products. We believe that TSE-positive material should be incinerated. In 1996, the UK banned the use of MBM for fertilizer on agricultural lands. At the end of June, the European Union will ban the use of eyes, brain and spinal chord in all cosmetic products.
We disagree with the FDA's exemption of blood and blood products from the rule as well. At a World Health Organization meeting in March, Dr. Paul Brown of the National Institutes of Health announced that his lab had injected blood from mice infected with CJD into the brains of healthy mice, and the latter subsequently developed a TSE. This work conclusively demonstrates that blood and blood products do carry the TSE-causing agent. If this is true for CJD, we must assume that it would be true for other TSEs.
The rule also exempts gelatin, which comes primarily from the hide of pigs and cows. Yet, in late April, FDA's own TSE Advisory Committee concluded that not enough scientific evidence exists to state that gelatin does not contain the TSE-causing agent and voted 10-to-3 that FDA should withdraw its exemption of gelatin from current regulations on BSE-derived materials.
Finally, the FDA's TSE Advisory Committee, which includes some of the world's top TSE scientists, and whose scope includes food products, was not asked to review the feed rule. Without such expert advice, we feel the rule lacks scientific credibility.
Given all the scientific uncertainties surrounding BSE, the real question becomes whether one errs on the side of safety, or decides to take some chances. Given the potentially disastrous implications of a worst case scenario, we would argue for taking all precautionary measures, as suggested by the UK, the EC and WHO. FDA should prohibit the feeding of any mammals to all food animals. Not only is the safety of the food supply at stake, but also the safety of agricultural land (through fertilizer), cosmetics, and pharmaceuticals made from animals.
If CJD incidence started to creep up in the human population, the safety of blood and other medical procedures could be compromised. Given the difficulties of reversing a TSE epidemic, it seems to us the best course is to take all necessary steps to keep one from getting started.
