Shortening of the Bovine Tongue According to Regulation (EC) 999/2001 is not Complying with the Current Legal Definition of Specified Risk Material - a Macroscopical and Histological Preliminary Study

Distribution of the lingual lymphoid tissue in domestic ruminants

The distribution and organisation of the intralingual lymphoid tissue was studied in sheep, goat and cattle. For each species, the tongues of two animals were harvested and divided in sample blocks extending over the total surface of the tongue. With 2.5 mm intervals, ten serial histological sections were made for conventional histological staining (haematoxylin-eosin, Van Gieson, Masson's trichrome) and immunohistochemical staining of lymphoid cells (anti-CD3, anti-CD21, anti-CD45). Lymphocytes were scattered in the subepithelial propria-submucosa and in the connective tissue cores of the lingual papillae. The connective tissue cores of fungiform papillae, including those located on the lingual apex, and vallate papillae showed relatively more lymphocytes than the propria-submucosa. Lymphoid cell aggregations were even more abundant beneath the grooves surrounding the vallate papillae in small ruminants. In cattle, a well-organised lingual tonsil was additionally found at the root of the tongue. CD3-positive lymphocytes were observed in all species examined. CD21-positive lymphocytes were numerous in the lymphoid nodules of the bovine lingual tonsil but very scarce in the ovine and caprine tongues. Therefore, the lymphoid cell aggregations in the tongues of small ruminants should not be referred to by the term 'lingual tonsil'.

Specified risk material and topographical distribution of lymphoreticular tissue of the bovine tongue

The elimination of specified risk material from food is crucial to restricting the risk to public health arising from bovine spongiform encephalopathy. The distribution of lymphoreticular tissue as potential specified risk material of the bovine lingual tonsil is described in relation to topographical anatomical landmarks. The definition of a proper landmark is a prerequisite for establishing adequate legal regulations concerning the removal of the lingual tonsil after slaughter. The main parameter to identify the lymphoreticular tissue in this study was the immunohistochemical identification of the follicular dendritic cells in the lingual tonsil. Lymph nodules were detected in areas up to 30 mm rostral of a given macroscopic landmark, i.e., the most caudal of the papillae vallatae. This area must therefore be adequately removed from the bovine tongue in the slaughterhouse. The current method for the removal of the lingual tonsil tissue according to Regulation (EC) 999/2001 at the slaughterhouse and alternatives to this method are discussed.

Anatomical and histological aspects of the bovine lingual tonsil

The localization of the bovine lingual tonsil is described as a prerequisite for the removal of specified risk material from the tongue meat in order to restrict the risk arising from bovine spongiform encephalopathy (BSE) to public health. The major part of this tonsil can be located macroscopically by the openings of its follicular crypts at the root of tongue. This part consists of organized aggregations of lymph nodules. Additional solitary primary lymph nodules and diffuse accumulations of lymphocytes are macroscopically invisible but are bilaterally present in the area extending 2 cm caudal to 3 cm rostral to the last vallate papillae. By sectioning the tongue 3 cm rostral to the last vallate papillae, undermining the lingual mucosa to the level of these papillae and making a transverse cut towards the lingual process of the basihyoid bone, the greater part of the lingual tonsil can efficiently be removed. Finally, immunohistochemical staining demonstrated the presence of T and B lymphocytes, suggesting that the bovine lingual tonsil can be considered as a site where an immune response can be induced.