Beefing about the risks posed by the French BSE epidemic

Abstract

Sir-In my capacity as chairman of the UK Food Standards Agency, I read Christl Donnelly's paper (Nature 408, 787-788; 2000) while it was being prepared for publication, and would like to comment on issues of food safety and policy raised by Donnelly's conclusions. Although the study of the French BSE epidemic is made in the context of the situation in the United Kingdom, there are some points that may have broader implications for the European situation as a whole. Following the 4 December meeting of the Agriculture Council, the European Commission has announced a series of new measures which will have a significant impact in reducing risk in the future. These include a complete ban on the use of mammalian meat and bone-meal for all livestock, the exclusion of all bovine intestine from the food chain and the introduction of an over-30-month (OTM) rule for all member states. Cattle over 30 months will only be allowed into the food chain if they have been tested for BSE and found negative. This year, the United Kingdom has had ten times as many cases of BSE as France, and yet, according to Donnelly, the current risk of eating an animal close to developing clinical BSE is substantially higher in France than in Britain (52 such animals going into the food chain in France versus 1.2 in the United Kingdom). The explanation for this is that Britain, uniquely, has not allowed any animals over the age of 30 months to go into the food chain, and virtually no animals are close to clinical BSE by this age. The studies of tissue infectivity carried out so far show that most infectivity occurs in animals within the last 12 months before clinical symptoms appear. Almost all infectivity in these animals is removed in the "specified risk material" that is excluded from the food chain. Donnelly's conclusions depend on three key assumptions: (1) that the age distribution for the onset of clinical BSE in France, reflecting a combination of the incubation period and the age at infection, is the same as in the United Kingdom; (2) that French and UK cattle populations have similar survivorship curves; (3) that 100% of clinical cases were reported in France in 2000, with under-reporting in earlier years, as was the case in the UK. The assumption of complete reporting this year may prove to be optimistic, in which case, risk from French beef will increase roughly in proportion to the degree of under-reporting this year