010653 Mad Cow, Should the U.S. Be Concerned?

Washington - Concerns about vaccine safety, antibiotic use and resistance, and the importation of infectious diseases have recently intensified, health officials said at a meeting with the National Foundation for Infectious Diseases (NFID). They outlined the challenges the United States currently faces, citing the potential fallout from reports of adverse reactions to vaccines; the growing number of bacteria that have developed resistance to a variety of drugs; the possibility of an outbreak caused by an exotic virus such as Ebola; and an increase in the number of Europeans diagnosed with varient Cruetzfeldt-Jakob Disease as areas of particular concern. They emphasized, however, that the development of rational policies by governments and responsible public awareness campaigns can reduce these risks greatly.

Mad Cow Disease, Should the U.S. Be Concerned?

Bovine spongiform encephalopathy (BSE), commonly known as “mad cow disease” is a fatal, chronic, degenerative disease affecting the nervous system of cattle. There have been more than 178,000 cases in cattle reported since BSE was first diagnosed in the United Kingdom in 1986. The disease has been confirmed in 13 other countries in Europe, however, over 95% of all cases are in the U.K. BSE belongs to a family of diseases known as the transmissible spongiform encephalopathies (TSEs). This family of diseases is found in a number of species, including humans. Examples in humans include Creutzfeldt-Jakob Disease (CJD) and Kuru.

BSE has recently been implicated in human cases of variant CJD or vCJD, mainly in the United Kingdom. Neither BSE or vCJD have been reported in the United States, and U.S. agencies have acted quickly with precautionary steps to prevent BSE in cattle.

From the start, the U.S. Food and Drug Administration (FDA) has made policies concerning suitability of blood or plasma donors thought to be at risk of Creutzfeldt-Jakob disease. They are currently attempting to develop a rational policy that would broadly address the theoretical risk posed by blood donors who may have been infected with the BSE agent while maintaining an adequate supply of blood, components and plasma derivatives. “The FDA believes that the theoretical risk of transmitting variant Creutzfeldt-Jakob disease through blood products can be substantially reduced by deferring blood donors who may have been exposed to the agent of bovine spongiform encephalopathy,” said David M. Asher, M.D., Office of Blood Research and Review, Center for Biologics Evaluation and Research, FDA.

The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) has also taken measures in prevention, education, surveillance and response. To prevent BSE from entering the country, APHIS has prohibited the importation of live ruminants from countries where BSE is known to exist in native cattle, since 1989. In 1997, these restrictions were extended to all countries in Europe. As of December 7, 2000 USDA made further restrictions: prohibiting all imports of rendered animal protein products, regardless of species, from Europe. This decision followed the recent determination by the European Union that feed of nonruminant origin was potentially cross- contaminated with the BSE agent. APHIS also leads an ongoing, interagency surveillance program for BSE in the United States. As of May 31, 2001, more than 13,100 brains from the United States and Puerto Rico have been examined with no evidence of BSE or other TSE detected.

APHIS, in cooperation with the Food Safety and Inspection Service, has also drafted an emergency response plan to be used in the event that BSE is identified in the United States. “APHIS continually revises and adjusts prevention and diagnostic measures as it receives new information and knowledge,” said Linda A. Detwiler, D.V.M, Senior Staff Veterinarian, APHIS.

Are Vaccines Safe?

Vaccines in use today have a tremendous safety record and have been enormously effective in eliminating serious disease or reducing rates to very low numbers. “The eradication of smallpox from the world; the eradication of poliomyelitis from the Americas, Australia, and Europe; and the marked reduction in disease burden due to measles, mumps, rubella, whooping cough, diphtheria, tetanus, and childhood meningitis substantiate this point,” said R. Gordon Douglas, Jr., MD, former president of Merck Vaccines. Furthermore, he pointed out, “vaccines are the only medical interventions that are actually cost- effective, that is for every dollar spent, more than one dollar is saved in other expenses for the health care system.”

Adverse reactions to vaccines do occur and are almost always minor or trivial. However, serious adverse reactions may occur at low rate. High rates of serious adverse reactions have precluded licensure. Because vaccines are given to millions of people each year, unrelated illnesses occurring randomly may seem to be associated with vaccinations. Dr. Douglas challenged the audience to avoid this mistake by saying, “for journalism to be responsible, it is essential to be able to differentiate between anecdotal co- occurrences and true causal relationships.”

Antibiotic Use and Resistance: Reaching the Tipping Point?

“The problem of antibiotic resistance results in the use of more expensive drugs and greater health care cost, and limits greatly the therapeutic options available to treat serious infections,” said John E. McGowan, Jr., M.D., professor of epidemiology, Emory University School of Medicine. Current resistance problems are exemplified by the emergence of drug resistance in bacteria virulent enough to cause infection even in persons with normal host defenses; the movement of organisms previously confined to hospitals and healthcare systems to the community-at-large; and finally, the most worrisome development is the presence of multiple resistance determinants in several Gram- negative bacteria. The days of “one-organism, one-resistance-factor” are going fast, and for some organisms may already be gone.

Have we reached the tipping point? The tipping point is a clear example of contagious behavior -- a small number of people who have wider influence start behaving very differently and that behavior somehow spreads to many others, with a dramatic and rapid impact. Specific activities that can help with resistance are now being identified and validated in studies from the U.S. and around the world. Among these are bringing in new antimicrobials; giving new emphasis to the use of vaccines for organisms which are becoming resistant; validating laboratory methods for detection of antimicrobial resistance; emphasizing proper implementation of infection control measures; and benchmarking studies of resistance and use.

“The new patterns of bacterial resistance, combined with accumulating data on effective ways to deal with resistance may mean that a “tipping point” in our battle against bacterial resistance is near,” concluded Dr. McGowan.

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