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Mad Cow: Linked to thousands of CJD cases?
December 29, 2003 United Press International By STEVE MITCHELL
Creutzfeldt-Jakob disease or CJD can be caused by eating beef contaminated with mad cow disease, but the critics assert without a better tracking system it might be impossible to determine whether any CJD cases are due to mad cow or obtain an accurate picture of the prevalence of the disorder in the United States.
Beginning in the late 1990s, more than 100 people contracted CJD in the United Kingdom and several European countries after eating beef infected with bovine spongiform encephalopathy -- the clinical name for mad cow disease.
Only one case of mad cow has been reported in U.S. cattle -- on Dec. 24 in a cow in Washington state -- and the Centers for Disease Control and Prevention's monitoring system has never detected a case of CJD due to eating contaminated American beef. Nevertheless, critics say, the CDC's system misses many cases of the disease, which currently is untreatable and is always fatal.
The first symptoms of CJD typically include memory loss and difficulty keeping balance and walking. As the disease destroys the brain, patients rapidly progress in a matter of months to difficulty with movement, an inability to talk and swallow and, finally, death.
Spontaneously-occurring or sporadic CJD is a rare disorder. Only about 300 cases appear nationwide each year, but several studies have suggested the disorder might be more common than thought and as many as tens of thousands of cases might be going unrecognized.
Clusters of CJD have been reported in various areas of the United States -- Pennsylvania in 1993, Florida in 1994, Oregon in 1996, New York in 1999-2000 and Texas in 1996. In addition, several people in New Jersey developed CJD in recent years, including a 56-year-old woman who died on May 31, 2003. Although in some instances, a mad cow link was suspected, all of the cases ultimately were classified as sporadic.
People who develop CJD from eating mad-cow-contaminated beef have been thought to develop a specific form of the disorder called variant CJD. But new research, released last December, indicates the mad cow pathogen can cause both sporadic CJD and the variant form.
"Now people are beginning to realize that because something looks like sporadic CJD they can't necessarily conclude that it's not linked to (mad cow disease)," said Laura Manuelidis, section chief of surgery in the neuropathology department at Yale University, who conducted a 1989 study that found 13 percent of Alzheimer's patients actually had CJD.
Several studies, including the one by Manuelidis, have found autopsies reveal 3-percent-to-13-percent of patients diagnosed with Alzheimer's or dementia actually suffered from CJD. Those numbers might sound low, but there are 4-million Alzheimer's cases and hundreds of thousands of dementia cases in the United States. A small percentage of those cases could add up to 120,000 or more CJD victims going undetected and not included in official statistics.
Experiences in England and Switzerland -- two countries that discovered mad cow disease in their cattle -- have heightened concerns about the possibility some cases of sporadic CJD are due to consuming mad-cow-tainted beef. Both countries have reported increases in sporadic CJD since mad cow was first detected in British herds in 1986.
Switzerland discovered last year its CJD rate was twice that of any other country in the world. Switzerland had been seeing about eight to 11 cases per year from 1997 to 2000. Then the incidence more than doubled, to 19 cases in 2001 and 18 cases in 2002.
The CDC says the annual rate of CJD in the United States is one case per million people, but the above studies suggest the true prevalence of CJD is not known, Manuelidis told UPI.
Diagnosing CJD or Alzheimer's is difficult because no test exists that can identify either disease in a living patient with certainty. So physicians must rely on the patient's symptoms to determine which illness might be present. Sometimes, however, the symptoms of one disease can appear similar to the other disorder. The only way to determine the disease conclusively is to perform an autopsy on the brain after death.
Unfortunately, although autopsies once were performed on approximately half of all corpses, the frequency has dropped to 15 percent or less in the United States. The National Center for Health Statistics -- a branch of the CDC -- stopped collecting autopsy data in 1995.
"If we don't do autopsies and we don't look at people's brains ... we have no idea about what is the general prevalence of these kinds of infections and (whether) it is changing," Manuelidis said.
At the same time autopsies have been declining, the number of deaths attributed to Alzheimer's has increased more than 50-fold since 1979, going from 857 deaths then to nearly 50,000 in 2000. Though it is unlikely the dramatic increase in Alzheimer's is due entirely to misdiagnosed CJD cases, it "could explain some of the increase we've seen," Manuelidis said.
"Neurodegenerative disease and Alzheimer's disease have become a wastebasket" for mental illness in the elderly that is difficult to diagnose conclusively, she said. "In other words, what people call Alzheimer's now is more broad than what people used to call it, and that has the possibility of encompassing more diseases -- including CJD."
The autopsy studies that found undiagnosed CJD cases raise the question of whether the United States "already has an undetected epidemic here," Jeff Nelson, director of vegsource.com, a vegetarian advocacy Web site, told UPI.
"What's the source of that?" Nelson asked. "Could it be the same source of encephalopathy we saw in minks?"
Nelson referred to an outbreak of a mad-cow-type disorder in minks in Wisconsin in the 1980s. The origin was traced back to the animals' diet, which included parts of so-called downer cattle -- sick cows that are unable to stand, which often indicates a neurological disease, including mad cow. The mink disease raised concerns about whether U.S. cattle were carrying a mad-cow-like pathogen even prior to the U.K. epidemic that began in 1986.
Andrew Monjan, chief of the neuropsychology of aging program at the National Institute of Aging -- part of the National Institutes of Health in Bethesda, Md. -- acknowledged there has been an increase in U.S. Alzheimer's cases. However, he told UPI, this probably is due to the aging of the population -- as people grow older, they develop a higher risk of developing Alzheimer's.
"There's been no change in the number of CJD cases in the country and there has been clearly a tracking of the unusual cases of CJD" that could be due to mad cow disease, Monjan said. However, Terry Singletary, coordinator of CJD Watch -- an organization founded to track CJD cases -- says efforts to track the disease have been close to nonexistent. For example, only 12 states require such reports. Therefore, many cases might be going undetected, unreported or misdiagnosed.
If more states made CJD a reportable illness, there would be more clusters detected across the United States, said Singletary, who became involved with CJD advocacy after his mother died from a form of CJD known as Heidenhain variant. In the 18-year period between 1979 and 1996, he noted, the country saw a jump from one case of sporadic CJD in people under the age of 30 -- a warning sign for a link to mad cow because nearly all of the U.K. victims were 30 years of age or younger -- to five cases in five years between 1997 and 2001. "That represents a substantial blip," he told UPI.
Singletary also said there have been increases in sporadic CJD in France, Germany and Italy, all of which have detected mad cow disease in their cattle.
So far, the CDC has refused to impose a national requirement that physicians and hospitals report cases of the disease. The agency has not chosen to make CJD a reportable disease because "making it reportable is not necessarily directly helpful in surveillance because in some states where it's reportable you may not get the physician to report it," said Dr. Ermias Belay, CDC's medical epidemiologist working on CJD.
Instead, the agency relies on other methods, including death certificates and urging physicians to send suspicious cases to the National Prion Disease Pathology Surveillance Center at Case Western Reserve University in Cleveland, which is funded by the CDC. However, because autopsies generally are not done, if a CJD case is misdiagnosed as Alzheimer's or dementia, a correct diagnosis might never be determined and therefore the cause of death listed on a death certificate might be inaccurate.
Belay told UPI he discounted this possibility. It is unlikely to happen, he said, because it is easy to distinguish CJD from Alzheimer's -- the two conditions display different symptoms.
Manuelidis disagreed. It can be quite difficult to determine accurately if a patient has CJD, as evidenced by her study, in which respected and competent neurologists and psychiatrists at Yale originally diagnosed patients with Alzheimer's, yet were wrong at least 13 percent of the time. Another study conducted at the University of Pennsylvania, which found 6 percent of dementia patients actually were suffering from CJD, supports the difficulty in distinguishing the illnesses correctly.
The U. Penn. researchers concluded: "These results show that in patients with a clinical diagnosis of dementia, the etiology (cause) cannot be accurately predicted during life."
In addition, the NPDPSC sees less than half of all the CJD cases each year, so the CDC's investigational system not only is missing many of the misdiagnosed CJD cases, it also is not conducting autopsies on most of the detected cases.
Belay said the CDC follows up on all cases of CJD that occur in people under age 55, as these could be linked to variant -- mad-cow-related -- CJD. But so far, all have turned out to be sporadic forms of the disease. About 30 cases of the disorder occur each year in the United States in this age group, while the remaining 270 or so are older.
The case of Carrie Mahan -- a Philadelphia woman who developed a brain disorder that appeared to be CJD and died from it in 2000 at the age of 29 -- illustrates just how difficult it can be to diagnose the disease.
Mahan's physician, Dr. Peter Crinos of the University of Pennsylvania Medical Center, ruled out other disorders and felt certain the young woman had died of CJD, a concern that raised the possibility of a link to mad cow disease because of her young age. When neuropathologist Nicholas Gonatas, who had seen CJD before, examined Mahan's brain after her death, he, likewise, was confident he detected the microscopic, sponge-like holes caused by the disease. But when he sent brain samples to the NPDPSC, the results came back negative. Gonatas, convinced the surveillance center's finding was erroneous, sent off two more samples, only to have them both come back negative.
Subsequent research, however, has shown the test used by the surveillance center cannot rule out CJD, said Crinos, an assistant professor of neurology.
"There's no question that Carrie had a spongiform encephalopathy," Crinos said, but added although it appeared to be CJD, it is difficult if not impossible to say if it was due to mad cow disease.
Crinos told UPI until the CDC implements a better tracking system, a lot of questions will remain about CJD and cases like Carrie Mahan's. One central question: Why are cases of what is presumed to be a rare disease popping up in clusters in certain areas of the country? Crinos said the clustering suggests an environmental or food-borne cause, but so far, "No one knows the answer to that."
Steve Mitchell is UPI's Medical Correspondent. E-mail email@example.com