ZM0303: An investigation of the extent of tonsil tissue present in tongue meat
Wednesday 25 June 2003
This research project aims to determine the extent of contamination of cattle tongue meat with tonsil tissue.
Background
Recent research at VLA has shown that palatine tonsilar tissue derived from cattle experimentally challenged with BSE contained low levels of infectivity in animals killed 10 months post inoculation. In the UK, under current legislation, the heads of bovines, where the palatine tonsil is located, are classified as Specified Risk Material (SRM) and destroyed. However, the tongue is removed from the head and allowed to enter into the human food chain. This project will investigate the distribution of tonsil tissue in the tongue of normal bovines, i.e. an anatomical study, and determine the extent of inclusion of tonsil tissue in the tongue as removed for human consumption using different practices, i.e. a study of industry practices.
Research Approach
This study included a detailed dissection of the intact heads of cattle removed in abattoirs. Gross examination for visible lymphoid tissue was supported by histological confirmation. The tongues from 100 normal bovine heads sourced from a local abattoir were examined to provide firmer data on the location of tonsilar tissue in the tongue. Following this bovine tongues were purchased from selected abattoirs throughout the UK. All tongues were examined grossly to determine where cuts had been made in relation to the anatomy determined previously. If any tongues appeared to have been removed in such a manner which would suggest that tonsil tissue might be present, provision was made for histological examination of sections taken at the cut edge to identify tonsil tissue. The results of this study will provide data on the extent of variation in butchery practice in the abattoirs used and the likelihood of tongues, as removed for human consumption, to contain tonsil tissue.
Results and findings
The preliminary results from the VLA indicate that visible lingual tonsil was present in 75% of the tongues collected from abattoirs prior to their release to the market. An anatomical study revealed that removal of visible lingual tonsil does not guarantee freedom from tonsillar tissue with nearly 60% of tongues having tonsillar tissue present. Previous indications that caudal edge papillae could be used to demarcate where to cut were not proven. Histology has shown that, in addition to the gross tonsil tissue currently being removed as Specified Risk Material (SRM), the tongue also contains other small areas of tonsil tissue, some of which are visible to the trained naked eye.
A risk assessment was carried out by Det Norske Veritas Ltd (DNV) to establish the potential level of exposure to BSE infectivity that the human population might be exposed to as a consequence of the possibility of infectivity in tonsil tissue. The results of both the VLA study and the DNV risk assessment were considered by SEAC in order to determine the risk implications associated with consumption of bovine tongue.