NR AJZF
AU Ridley,R.M.; Baker,H.F.
TI Oral transmission of BSE to primates
QU Lancet 1996 Oct 26; 348(9035): 1174
PT letter
VT
Sir - In a report to the European Union Commission, Prof C Weissmann of Zürich University has recommended that experiments be set up to investigate oral transmission of BSE to primates to see whether human beings are at risk from eating beef products.[1] Bovine spongiform encepholopathy (BSE) has already been transmitted to primates by intracerebral injection of infected brain tissue homogenate[2] so the "species barrier" between cattle and primates is not absolute. BSE has also been transmitted by feeding infected brain to mice[3] so clearly transmission of this agent by the oral route is possible. During the BSE epidemic not only were cattle fed on contaminated, rendered material, but large numbers of other species in zoos, farms, and domestic ownership were also fed on pelleted food containing rendered material. A few animals of several species of antelope and cat[4] but not monkeys[5] became affected despite these monkeys being fed for many years on pellets which contained up to four times the amount of the implicated, rendered meat and bone meal that was included in cattle pellets. Thus a "species barrier" of some sort exists between cattle and primates. But will Weissmann be able to quantify this in a way which will have public health implications?
In 10 years' time he may be able to determine the smallest amount of raw cow brain necessary to cause disease if fed to perhaps a few dozen monkeys. But what will this tell us about the maximum quantity of bovine-derived material (from which specified offals have been removed) which can be consumed without causing illness when the sample size could be up to 50 million people in the UK? As every drug company knows, extensive tests in clinical trials in large numbers of people cannot ensure that a new drug, when available on general prescription, will not cause serious illness in a handful of patients such that the drug has to be withdrawn. At best Weissmann's experiments will be irrelevant; at worse they will provide a degree of reassurance which is unwarranted. There is nothing that can be done to reduce any risk to which people have been exposed in the past, and there is now no alternative but to do the best we can to eliminate BSE entirely.
1 Report by The EC Group on BSE Research to the EU Agriculture Commissioner, Oct 10, 1996.
2 Baker HF, Ridley RM, Wells GAH. Experimental transmission of scrapie and BSE to the common marmoset. Vet Rec 1993; 132: 403-06.
3 Barlow RM, Middleton DJ. Dietary transmission of bovine spongiform encephalopathy to mice. Vet Rec 1990; 126: 111-12.
4 Schreuder BEC. Animal spongiform encephalopathies - an update. Vet Quart 1994; 16: 174-92.
5 Ridley RM, Baker HF, Windle CP. Failure to transmit bovine spongiform encephalopathy to marmosets with ruminant-derived meal. Lancet 1996; 348: 56.
ZR 5
MH Administration, Oral; Animal; Cattle; Comparative Study; Encephalopathy, Bovine Spongiform/*transmission; *Food Contamination; Human; *Meat Products; *Primates
AD *R M Ridley, H F Baker, MRC Comparative Cognition Team, Department of Experimental Psychology, Downing Street, Cambridge, CB2 3EB, UK
SP englisch
PO England