Scientific Opinion on BSE risk in bovine intestines and mesentery

Abstract

Bovine intestines and mesenteries in the European Union (EU) have to be removed from the food and feed chain. The opinion provides a quantitative assessment of the Bovine Spongiform Encephalopathy (BSE) infectious load that might enter the food and feed chain yearly if bovine intestine and mesentery from animals born and raised in the EU would be re-allowed for consumption. Data on the evolution of the BSE infectious titre; and of the weight of histological structures accumulating BSE infectivity, were collected. The Cattle TSE Monitoring Model (C-TSEMM) was used to estimate the number of BSE infected cattle entering undetected in the food and feed chain yearly. A model named TSEi was developed to estimates the BSE infectious load in tissues from infected animals at different ages and the total yearly infectious load that could enter the food and feed chain in the EU27. In BSE infected cattle, the infectivity associated with intestine and mesentery reaches its maximum in animals younger than 18 months and then progressively declines to a minimum value in animals older than 60 months. Due to the decline of the BSE prevalence in the EU, between 2007 and 2012, the yearly amount of BSE infectivity associated with intestine and mesentery (sent to destruction) from animals entering the food and feed chain was reduced by a factor of 10. However, over this period, the maximum level of exposure to the BSE agent for individuals that would have consumed these tissues remained stable. Finally, the TSEi model indicated that the removal of the last four metres of the small intestine and of the caecum from the food and feed chain would result in a major reduction of the BSE exposure risk associated with intestine and mesentery in cattle. (2011) and Kaatz et al. (2012). James Hope and Marion Simmons are acknowledged for kindly disclosing to EFSA raw data on BSE infectivity in bovine intestine; and the titration in RIII mice of the BBP12/92 inoculum used in the Buschmann and Groschup (2005) paper. * Three minor editoral changes were made: The number of atypical cases in 2005 in Table 11 © European SUMMARYFollowing a request from the European Commission (EC), the Panel on Biological Hazards (BIOHAZ) was asked to deliver a scientific opinion on the BSE risk in Bovine intestine and mesentery.Currently bovine intestines and mesenteries in the European Union (EU) are classified as Specified Risk Material (SRM) according to Regulation (EC) 999/2001 4 (Reg. 999/2001) as amended -the TSE Regulation -and have to be removed from the food and feed chain. SRM are considered as the animal tissues potentially containing the highest level of Transmissible Spongiform Encephalopathies (TSEs) infectivity. Thus, the removal of SRM is the most important public health protection measure against TSEs in the EU.In this context, the BIOHAZ Panel was requested to assess quantitatively the Bovine Spongiform Encephalopathy (BSE) infectious load that might enter the food and feed chain yearly if bovine intestines (fresh or after processing into c...

Low levels of classical BSE infectivity in rendered fat tissue

“…Our results, in particular the close relationship with the infectivity/PrP Sc data of the CMGC samples, clearly support the widespread accepted assumption that infectivity in the mesentery is most probably associated with nerves and autonomous ganglia [9], whereas the direct involvement of fatty cells is uncertain [11]. Another source of infectivity could be in mesentery fat embedded lymph nodes.…”

“…In particular with regard to the negative early and late preclinical samples, there still remain some uncertainties, which can only be resolved by a more extended, that say statistical profound study. However, the inocula were generated according to standard tallow production methods [9], therefore our results clearly show that such a contamination is conceivable. Rendered fat can been used for food (i.e.…”

“…In orally BSE infected cattle first traces of infectivity can be detected in splanchnic nerves and in the celiac and mesenteric ganglion complex (CMGC) at 16 and 20 months post-infection (mpi), followed by an increase of infectivity until to the clinical stage when even a PrP Sc accumulation can be seen in the ganglion [8]. Therefore, it is widely accepted that infectivity in mesentery, if present at all, is most probably associated with fat embedded nerve fibers and autonomic ganglia [9]. However, studies using fat from BSE affected cattle failed to detect any infectivity in RIII wild type mice [10].…”

“…These include, among others, intestine and mesentery of animals of certain age/species from animals whose origin is in Member States or third countries with controlled or undetermined BSE risk. In this regard it has to be bear in mind that mesentery contains a network of nerves, ganglia, blood and lymph vessels as well as lymph nodes to support the gut [9]. However, up to now, it remains unclear whether a BSE contamination of rendered fat could occur during tallow production.…”

“…Anamnestic data are given in Table 1. Fat was rendered from CMGC samples, which were embedded in mesentery fat, by incubation for 20 min at 95 °C, according to standard tallow production methods [9]. Subsequently the melted fat was taken, but still contained tissue remnants.…”