LONDON--Ever since the first indication in 1995 that "mad cow disease" had crossed the species barrier into people, causing a deadly new form of brain disorder, one critical question has remained unanswered: How many more cases are likely to show up? Given the long latency period for the disease--perhaps 10 years or more--it is hard to tell whether Britain is facing a silent epidemic or just a smattering of cases beyond the 27 diagnosed so far.
Late last week, the British government announced that it is about to launch a novel study to try to find out. It will examine hundreds of stored tonsils and appendixes, removed during surgery in the past several years, for traces of the misshapen proteins called "prions" that have been associated with the brain disorder, known as new-variant Creutzfeldt-Jakob Disease (nvCJD).
The study was prompted by the case of Tony Barrett, a 45-year-old coastguard from southwest England, who died of nvCJD in June. According to a paper in the 29 August issue of The Lancet, Barrett had his appendix removed at a local hospital 8 months before he first showed symptoms of the disease. When physicians examined the stored tissue for evidence of the misshapen prions, it tested positive. It was the first demonstration that nvCJD can be detected before symptoms appear, says James Ironside of the National CJD Surveillance Unit, a co-author of the Lancet paper.
The government now plans to test more than 1000 of the 800,000 samples of tonsil and 45,000 samples of appendix removed and stored each year. Comparison of tissue removed before and at the height of the mad cow disease epidemic in the late 1980s may provide a rough assessment of the extent to which the population harbors nvCJD prion proteins. The study will be too small, however, to provide anything more than an indication of whether or not there is a widespread problem. "Interpretation of the [data] will require considerable caution," says Kenneth Calman, Britain's chief medical officer, who announced the study last week.
Government officials and their advisers have not yet worked out the ethical rules that will govern the testing program, however. One option is to remove all identifiers so the tissue cannot be traced back to the patient. If that is not done, researchers will have to deal with the issue of whether to tell patients if prions are detected in their removed organs.