NR ASMQ
AU Johnson,R.T.; Gibbs,C.J.Jr.
TI To the Editor
QU The New England Journal of Medicine 1999 May 27; 340(21): 1681-91
PT Brief an den Editor
VT
Dr. Hansen is correct that several studies have implicated a history of consumption of various meat products in Creutzfeldt-Jakob disease. In a disease in which patients frequently are demented or have died, dietary histories are limited and subject to bias. This problem is graphically demonstrated in a study cited by Hansen, the British Surveillance Report (available to readers at http://www.CJD.ed.ac.uk/report97.html). This report contains an analysis of the dietary histories of 80 patients in whom the suspected diagnosis of Creutzfeldt-Jakob disease was not subsequently confirmed. Comparison of these cases with confirmed cases of sporadic Creutzfeldt-Jakob disease showed no differences in the consumption of beef or brains. The report concludes that dietary associations "may reflect recall bias rather than a real, underlying link."
The absence of geographic differences in incidence is more convincing evidence against major dietary factors, since large populations eschew pork and some consume no meat or meat products. We are unaware of studies of the incidence of Creutzfeldt-Jakob disease in populations of lifelong vegetarians; such a study would be of interest. In the meantime, we hold to our conclusion that, as yet, diet has not been convincingly linked to causation in sporadic cases of Creutzfeldt-Jakob disease.
The second issue raised by Dr. Hansen concerns the mode of transmission of new-variant Creutzfeldt-Jakob disease. The prions of the new human disease and bovine spongiform encephalopathy are closely related, as demonstrated by several methods of comparison discussed in our review. They appear to have a common origin, which could be related to the consumption of contaminated beef, but it could also be due to common exposure of cattle and humans to the contaminated products of the rendering process. Cosmetics, soap, bonemeal-based food for roses, and myriad other products of rendering could lead to human exposure by different routes of inoculation. It is imprudent at this time to conclude that eating meat or even oral exposure is the mode of transmission of the new-variant disease.
Dr. Gray's point is well taken. The elimination of older animals in herds would decrease the incidence of disease, since animals under five years of age are rarely affected clinically. The selective slaughter of affected herds might have little effect, however, since there is no evidence of horizontal spread within herds. Nevertheless, figures expressed as annual cases per cattle at risk would be preferable.
Drs. Cavanagh and Hogan feel we gave short shrift to transmission by corneal transplantation. Such an oversight was not intended. Twenty-five years ago both of us were involved in the case and studies of the initial patient who acquired the disease through corneal transplantation. The very thought of human-to-human transmission of a degenerative disease by physicians was so unspeakable that some detractors suggested that the presence of disease in the donor and the recipient might have been coincidental. The report three years later of illness in two young persons implanted with the same electrode and the subsequent transmission to a nonhuman primate through the implantation of the same electrode convinced the doubters. The subsequent report of transmission through corneal transplantation added further confirmation. The report of additional cases by Cavanagh and Hogan (in a report published subsequent to our review) provides yet more documentation. We heartily endorse their advocacy of cautious screening of corneal donors.
AD Richard T. Johnson, M.D. Johns Hopkins Hospital Baltimore, MD 21287, Clarence J. Gibbs, Jr. National Institutes of Health Bethesda, MD 20892
SP english
PO England