New mad cow strain similar to human CJD

Italian researchers said Monday they have discovered a new strain of mad cow disease that is very similar to a spontaneously occurring form of a deadly human brain disorder called sporadic Creutzfeldt-Jakob disease.

Italian researchers said Monday they have discovered a new strain of mad cow disease that is very similar to a spontaneously occurring form of a deadly human brain disorder called sporadic Creutzfeldt-Jakob disease. Scientists previously thought the consumption of meat infected with the mad cow pathogen could only cause a specific form of the fatal disorder known as variant CJD. The new finding, which appears in the online early edition of the Proceedings of the National Academy of Sciences journal, increases the possibility some cases of sporadic CJD also could be due to mad cow-infected meat, said Salvatore Monaco, a co-author of the study and a professor in the department of Neurological and Visual Science at Policlinico G.B. Rossi in Verona, Italy. Variant CJD was first detected in the United Kingdom in the latter half of the 1990s. Since then, about 150 people, nearly all in the United Kingdom, have come down with vCJD, which typically strikes those under the age of 30. Sporadic CJD, by contrast, generally occurs in those over the age of 55. It’s also a rare disease, with only about 300 cases reported annually in the United States. There is no treatment for either form of CJD, and victims usually die about a year after the onset of symptoms because the causative agent — thought to be an abnormal protein called a prion — rapidly destroys the brain. The new study “is just another piece of evidence that some of the sporadic CJD cases … could be associated with the consumption of infected meat,” Michael Hansen, a microbiologist with the watchdog group Consumers Union in Yonkers, N.Y., told United Press International. “We need to focus on not just mad cow disease and vCJD but all forms of transmissible spongiform encephalopathies,” Hansen said. These include scrapie, the sheep version of these brain-wasting diseases, and chronic wasting disease, which afflicts deer and elk, he said. Both scrapie and CWD are endemic in the United States, but it remains uncertain whether either one can infect people. Based on the new findings, CJD surveillance should be intensified to “give us the opportunity of detecting an increase of some CJD forms,” Monaco told UPI. This means doing detailed lab work on all human cases of the disease, including conducting molecular analysis of the prion and documenting the pattern of brain damage in each case, he said. Paul Brown, a CJD expert at the National Institutes of Health in Bethesda, Md., said the findings do not pose a concern for humans. “Were it not for the fact that diagnosed cases of sporadic CJD in the U.K. have not increased in the past 10 years, it would have worrisome implications,” Brown told UPI. “As it stands, it does not, because if the proposition is that we’re misdiagnosing (mad cow) in humans as sporadic CJD, it stands to reason that there would be more cases of sporadic in the U.K., where most of this is happening, and there isn’t. “Nor for that matter is there in Italy or in most other countries in Europe,” he added. Hansen disputed the assessment and pointed out there actually have been increases in sporadic CJD in both the United Kingdom and Switzerland in recent years. Scientists are uncertain as to whether these are real increases or increases due to better surveillance. Switzerland discovered in 2002 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. The incidence more than doubled, to 19 cases, in 2001 and 18 cases in 2002. John Collinge, of the Imperial College of London, conducted a study in 2002 that indicated the mad cow prion could cause both vCJD and sporadic CJD, and acknowledged if there is an increase of sporadic CJD cases in the United Kingdom, some could be due to consumption of mad cow infected meat. Concerns about CJD in the United States were heightened recently by the detection of the country’s first confirmed case of mad cow disease, also known as bovine spongiform encephalopathy or BSE, in Washington state in December. A report issued two weeks ago by an international panel of experts and commissioned by the U.S. Department of Agriculture concluded it was “probable” that other cases of mad cow had been imported into the United States from Canada and Europe, had been turned into cow feed, and indigenously infected U.S. herds. Consumers have some degree of protection because the USDA requires the brain and spinal cord — the most infectious parts of a cow — to be removed and not allowed into human food. Hansen, however, noted bits of brain and spinal cord have been found in hamburger meat processed by mechanical devices. Other infectious parts of the animal, such as bone marrow and segments of the intestine, have also been allowed for human consumption. There have not been any cases of vCJD linked to consumption of meat from U.S. cattle, but there have been clusters of cases of sporadic CJD in certain areas of the country in recent years: southern New Jersey, 2000-2003; Lehigh, Pa., 1986-90; Allentown, Pa., 1989-92; Tampa, Fla., 1996-97; Oregon, 2001-02; and, Nassau County, N.Y., 1999-2000. These clusters have raised concern because the sporadic form of the disease is thought to be so rare — most experts put the prevalence at about 1 per million population — that several cases occurring in the same area is out of the norm. The Centers for Disease Control and Prevention in Atlanta has a CJD surveillance program, but it has been criticized as being inadequate by some experts and consumer groups. The CDC has refused requests to require physicians to report all CJD cases. Instead, the agency relies on death certificates to get a count of people dying from the disease. The agency has acknowledged it only conducts autopsies on less than half of all the CJD cases that occur each year. Autopsies are the only way to positively confirm a CJD case. In addition, at least four autopsy studies have shown that anywhere from 5 percent to 30 percent of the 4.5 million Alzheimer’s cases and thousands of dementia cases in the United States may have been misdiagnosed and are actually CJD. In one study done in 1989, Laura Manuelidis, section chief of surgery in the neuropathology department at Yale University, found 13 percent of Alzheimer’s patients actually had CJD. Another study conducted at the University of Pennsylvania found 6 percent of dementia patients diagnosed with dementia were really suffering from CJD. Neither the CDC nor the USDA could be reached for comment on Monday. “They’re not really doing that good a job,” Hansen said of the CDC’s CJD surveillance program. The agency is missing so many cases of the disease it would be difficult to determine whether any sporadic CJD cases are due to this new strain or other strains of mad cow disease, he said. In the study, Monaco’s team examined the brains from eight Italian cattle infected with mad cow disease and found the new strain in two of the animals. The two cows were 15 and 11 years old and had tested positive for the disease sometime between 2001 and 2003. The researchers dubbed the new strain bovine amyloidotic spongiform encephalopathy or BASE to distinguish it from BSE and to reflect the fact that it uniquely causes deposits in the brain known as amyloid plaques. Molecular analysis revealed the new strain to be very similar to prions taken from humans diagnosed with sporadic CJD. The new strain also appears to affect a different region of the brain than the typical mad cow strain, and this may have implications for screening cattle for BSE. “Although current tests detect this new strain, brain areas usually sampled for BSE (the brainstem) have less amount of the pathological protein as opposed to cortical areas,” where the new strain is most predominant, Monaco said. Hansen said based on this and new strains of BSE that recently were discovered in Japan and France, “it seems the USDA would want to sample more of the cow brain” than it currently is doing to ensure cases are not being missed. The agency only samples a region of the brain known as the obex when testing for BSE. Monaco and his colleagues made a point of noting in their study the new strain might not show up in that region and said “brain sampling should not be limited to the obex.” (Source: Medline Plus, United Press International, Feb 2004)