The UK Ministry of Agriculture Fisheries and Food (MAFF) have been carrying out an experiment to find out how BSE infectivity develops in an infected animal and to identify in which tissues infectivity may be detected. In mid 1997 preliminary results showed positive infectivity in a tissue connected to the spinal cord and located within the vertebral column, the dorsal root ganglia. This tissue would not be removed with the spinal cord, and was not covered by the regulations specifying the tissues banned from human consumption, thus raising the possibility that people could be exposed to BSE infectivity in food.

In order to help assess the significance of this result, the Spongiform Encephalopathy Advisory Committee (SEAC) requested that a risk assessment study be carried out to assess the potential exposure of the UK population to BSE infectivity in dorsal root ganglia.

Any risk assessment of BSE infectivity is complicated by lack of knowledge and uncertainty. In order to assess the exposure it was necessary to estimate the infectivity to humans in an infected animal and the number of cattle that could have infectivity at the time of slaughter for human consumption. Slaughter and butchering practices were studied to assess what happens to the dorsal root ganglia during carcase dressing and boning-out and the likelihood of it being consumed.

The study results showed that whilst the estimated risk of exposure to BSE infectivity from dorsal root ganglia was very low, there is a wide range of uncertainty in the results which has to be taken into account in coming to a decision. It was shown that banning the sale of meat on the bone had little effect on the base case results, but that the effectiveness was very dependent on the assumptions made.