Researchers closer to test for human form of ‘mad cow’ disease

Scientists have developed two simple tests that could offer the first non-invasive ways to diagnose the human version of “mad cow” disease.

The tests -- one using a urine sample, the other nasal “brushings” -- seem to reliably detect Creutzfeldt-Jakob disease (CJD), according to separate reports in the Aug. 7 issue of the New England Journal of Medicine.

CJD -- popularly known as mad cow disease -- is an invariably fatal brain disease, so earlier diagnosis will not save patients’ lives -- at least not until therapies for the disease can be developed.

But experts said simple tests for CJD could help prevent transmission of the disease, which, very rarely, has happened through medical procedures, blood donation or contaminated beef.

“We also need rapid, sensitive and specific tests to help us make the correct diagnosis for people presenting with dementia,” said Dr. Colin Masters, a prion disease researcher at the University of Melbourne, in Australia.

“It is sometimes very difficult to be sure of the correct diagnosis using just (signs and symptoms),” said Masters, who wrote an editorial published with the studies.

CJD arises when normally benign proteins called prions become “misfolded,” killing off brain cells. There are several forms of CJD:

The most common one is “sporadic” CJD, which affects about one in a million people worldwide each year.

Another form is variant CJD, which is the form linked to eating beef tainted with “mad cow” disease. Mad cow -- or bovine spongiform encephalopathy -- is a prion disease that strikes cattle. There have been these tests to help us with infection control measures, particularly for the safety of the blood transfusion process in people incubating variant CJD,” he said.

In those “incubating” cases, people carry the abnormal prion but have not developed variant CJD symptoms. In the United Kingdom, a few cases of the disease have been linked to blood transfusions from donors who carried the prion but were not yet symptomatic.

And last year, a study estimated that roughly 30,000 U.K. residents could be carriers.

So far, Soto noted, the people stricken by variant CJD have been young -- typically in their 20s, whereas sporadic CJD affects older adults.

But, he added, it’s still possible that people incubating the variant prion could develop the disease later in life.

“We don’t know how long the incubation period might last,” Soto said.

“Maybe those people won’t develop CJD, but we don’t know.”

In the United States, there have been four cases of variant CJD, according to the CDC. The agency says there is evidence all of those people were infected outside the United States.

Similarly, four cases of mad cow disease have been found in U.S. cattle, according to the CDC. By comparison, at the height of the mad cow epidemic in the United Kingdom, in 1993, there were 1,000 new cases in cattle each week.

The authors of both studies say further studies are necessary to confirm their findings before either method could be available for detecting CJD.