In his Nobel Prize-winning lecture, published in full in Science (1977) vol 197, p943, D Carleton Gajdusek showed that kuru was much more prevalent among women than men, that while women participated in the butchery of the corpses men rarely if ever did so, but both sexes ate the flesh after cooking it. Gajdusek noted that women contaminated themselves, their infants and toddlers with heavily infected brain tissue when the skull of a dead victim was opened and, pointing out that they "rarely if ever washed" suggested that infection "was most probably through the cuts and abrasions of the skin, or from nose picking, eye rubbing, or mucosal injury".
If non-oral routes are indeed the principal ones for the transmission of encephalopathies, then one might expect to find the following:
1. Humans would probably not contract anything from eating scrapie-infected meat. For sheep at least, the experience of the last 200 years would seem to support this view.
2. Humans who handle "volatile" scrapie-infected material, such as dry, rendered bone meal made from contaminated sources, could well become infected by inhaling dust. Could this explain CJD in dairy farmers?
3. Humans who handle less dusty material, such as infected nervous tissue in abbatoirs, and who practise sensible hygiene, should be less at risk.
4. Beef from herds which have never been exposed to contaminated meal should not contract BSE, which is true for organic farms.
5. Cows fed on infected bone meal would become infected through the nose rather than the mouth. When cows eat meal they push their entire muzzle well into the food.
Research needs to establish the normal transmission route of these agents before we conclude that eating of, as opposed to non-oral contamination with, infected material is responsible for encephalopathies in humans.
Dr J S Knowland
Department of Biochemistry
University of OxfordReuse content