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Mad Cow Disease
Mad Cow Disease
Tony Tufariello, Stamford
Introduction
This piece will attempt to answer the following questions about an animal disease with potential human significance and then highlight the potential impact to Insurers:
· What is "mad cow disease" and what causes it?
· How is the disease spread and where is it found?
· How does it affect ranchers, dairymen, slaughterhouses, meat suppliers, and consumers?
· What is its significance in the United States?
· What import does it have for pharmaceutical companies?
This disease with a seemingly humorous common name, is serious business in several European countries and a concern in North America and other meat producing and dairy centres as well. The illness is known to veterinarians as bovine spongiform encephalopathy or BSE and is identified by a gradual loss of muscle control and coordination which is confirmed by microscopic examination of the brain after the animal is destroyed. The disease tends to deposit protease resistant protein (PRP) in the brains of infected cattle, but an infective organism has not yet been found although a slow virus or infective protein (prion) is surmised.
The disease would be of limited interest but for two essential characteristics, a) after transmission, it takes 5 to 6 years to manifest in cattle, after which it only takes 6 months to kill the animal, and (b) a disease with closely related characteristics, Creutzfeldt-Jakob Disease (CJD) is seen in humans, if only rarely. This disease is said to have a latency period of several months to several years, although its means of transmission are unknown. The similarity of symptoms between mad cow disease and CJD led to speculation that CJD may be contracted by eating beef from cattle infected with BSE.
A related disease in sheep and goats, scrapie, has been known for hundreds of years. Typically, it causes similar destruction of the brain and loss of muscle coordination. Its name derives from the incessant itching that it causes, leading animals to constantly rub against posts or trees to relieve their discomfort. Sheep are thought to transmit the disease by eating the postpartum afterbirth of their species to limit tracking by predators.
The Epidemic In Cattle
Scrapies was seemingly confined to sheep and goats until sometime in the mid-1980’s, when British rendering plants
which process offal (byproducts) from the slaughtering of sheep switched from a batch process to extract oils from the fat to a continuous process, which provided less heating. It is surmised that the shorter heating process allowed the scrapies organism to survive in the offal, which was then added to cattle feed mixtures. A mutation of the infective organism at the same time may have allowed it to infect bovine cattle as BSE. Although the organism is not highly contagious, offal added to feed customarily contains the brains and spinal cords of slaughtered sheep and these are the most highly infected organs. Injections of diseased tissue into the brains of test animals leads to development of the disease after a 5 or 6 year latency period in cattle. Some experts believe that the disease may be transmitted to offspring through the maternal blood. Animals manifesting symptoms may be tested after sacrifice using an available reagent to identify the tell tale proteinase resistant protein.
One case of the disease in bovine cattle has been confirmed in Canada, involving a cow imported from the U.K.. Because the potential for transmission exists, it is likely that the entire herd of which that cow is a member will be ordered destroyed - at considerable cost. In the U.S., some 500 cows have been imported from Britain between 1981 and 1989, with the U.S. Department of Agriculture estimating a 52% chance that at least one cow was infected. The uncertainty stems from the long latency period and the present impossibility of testing live animals. To date, no cases in bovines have been reported in the U.S..
In Britain, the disease has been epidemic, with some 120,000 cows said to have perished of the illness since 1985, from a total of 138,000 reported cases. Because other European Union countries fear a wider spread of the disease to their herds and possibly their residents, one E.U. member, Germany, had tried to ban the import of British beef. Opponents point out that the disease has already appeared in several European countries, including Germany, so a ban might be ineffective. A compromise agreement allows the export of British beef from herds certified as free from BSE for a period of at least six years. These precautions have been taken to limit the probability of the disease spreading to humans and beef cattle. In view of the small but significant potential for transmission of the disease to humans, the British have banned human consumption of brains and spinal cords from cattle since 1989.
The Human Connection
To this point, BSE might be an economically important curiosity with special meaning for ranchers, cattle breeders, some drug companies, meat, and animal feed dealers. However, in early 1994, there were press reports of BSE transmission to a 16-year old in Britain, manifested as Creutzfeldt-Jakob Disease, and other reports of the disease in a young person and two middle-aged dairy farmers, all of whom ate beef. In fact, the teenager was said to have been an avid eater of meat pies, which routinely contained by-products (offal) from infected cattle, until a 1989 British ban on their use in human food products.
Some drug companies are involved in this controversy as well, because certain pharmaceuticals are made from bovine organs or blood which might be infected by BSE. The risk in the U.S. should be minuscule, because cattle here have not yet been affected. Bovine sources of drugs in Europe may be of more concern. The related Creutzfeldt-Jakob Disease has been transmitted to humans by organ transplants from infected donors or the improper sterilization of electrodes used in the brain during some surgical procedures.
Controls & Characteristics
The nature of this disease and the possibility that it might be transmissible to humans have resulted in recognition of fundamental characteristics and needed controls:
· Several major sheep-raising states in the U.S. have encouraged the destruction of sheep manifesting scrapies. The USDA has established a voluntary certification program for flocks free of scrapies.
· In the UK, the use of offal in human foods was banned in 1989, although brains are still permitted. (Organ meats or offal are not permitted in processed meats sold in the U.S., e.g., frankfurters, bologna, or sausage.)
· The FDA proposed in December 1994 that the use of sheep and goat offal in cattle feed be ended, although rendering practices and the lower incidence of scrapies in U.S. flocks make transmission to bovines less likely. Action on the FDA proposal has been indefinitely delayed.
· There is international attention to the presence of BSE in herds and a common practice of destroying the infected animals and others in the herd to curtail its spread.
· The European Union has established processing requirements for renderers to help insure destruction of the infective agent of scrapies and BSE.
· Even given the latency period, some experts argue that the epidemic of BSE in the U.K. should have manifested in beef-eating consumers there by this time, if the disease were transmissible. Instead CJD (the human disease analog) has been occurring at the same low rate as before the epidemic.
· The USDA has been examining the brains of slaughtered cattle manifesting neurological symptoms and has found no BSE in some 2,000 brains examined to date in the U.S..
· In the U.S., most sheep and cattle offal goes into pet foods, but some slaughterers may process a few sheep and sell the offal for use in bovine feed.
· In the western U.S., large flocks of sheep may contain individual animals with scrapies - all without known transmission to beef or dairy herds.
· In Australia, which is an important sheep-producing region, there has been no evidence of scrapies or BSE, yet the incidence of CJD in humans is similar to that in the U.S. or U.K., indicating other causes for the human disease.
· The losses in sheep from scrapies were always higher in the U.K. because losses were more typically accepted there while U.S. ranchers usually attempted to eradicate it by destruction of diseased animals or flocks.
Conclusion
There remains disagreement among specialists in the field about whether or not bovine spongiform encephalopathy can be transmitted to humans through the consumption of beef. Some experts are convinced that it cannot, because the human disease to which it is linked, Creutzfeldt-Jakob Disease, has been occurring at historically low rates, despite the epidemic of BSE in dairy and beef cattle in the U.K..
Because the epidemic began at the same time that rendering processes were being changed in Britain, the switch to low-temperature continuous processes has been linked to transmission of the disease to bovines, possibly accompanied by a mutation in the infective (though unidentified) organism. New EU processing rules for offal mandate higher temperature treatment to end such transmission.
Even if humans are not subject to infection from beef, the potential economic effects from the sale of infected cattle, offal for feed, or animal feeds could be substantial. The sale of infected bovine-derived medicines could produce substantial bodily injury litigation, unless production sources are carefully screened. Fortunately, such controls appear to have been established, so action by underwriters at this time may be premature, especially in U.S. markets, where the disease has not manifested. In Europe, businesses selling cattle, their meat, or medicines made from them must assure disease-free stocks by live animal testing as soon as methods are approved.
Legal Disclaimer
This article describes historical or potential exposures and pertinent safety or loss controls of which we are now aware, as well as relevant examples of case law, statutes, and regulations. Not all exposures, losses, or loss controls are reported and others may be relevant in particular circumstances. This material may need revision from time to time, but we do not undertake to do so. We encourage you to consult with appropriate professionals including legal counsel and to obtain the original texts of materials referenced with respect to the matters discussed herein. |
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