Exposure Assessment of TSEs from the Landspreading of Meat and Bone Meal
Recent changes in European legislation have meant that certain processed abattoir waste, which has been appropriately heat treated and ground to a specified particle size, can be spread on nonpasture agricultural land. This has opened the way for the potential landspreading of mammalian meat and bone meal (mMBM) derived from animals slaughtered for human consumption. This article reports on two separate case studies (Study 1 carried out in Great Britain (GB) and Study 2 carried out in Ireland) on the potential exposure to TSE infectivity following the spreading of abattoir waste (derived from animals slaughtered for human consumption) on nonpasture agricultural land. For Study 1, the average TSE infectivity on nonpasture agricultural land per year from sheep with scrapie was found to be higher (five orders of magnitude) than that estimated for BSE in cattle (3.9 × 10−3 Ovine Oral ID50/ton of soil compared to 3.3 × 10−8 Bovine Oral ID50/ton of soil). The mean estimate for BSE in sheep was 8.1 × 10−6 Ovine Oral ID50/ton of soil. The mean level of infectivity in mMBM was assessed to be 1.2 × 10−5 and 2.36 × 10−5 ID50/ton of mMBM for Study 1 and 2, respectively. For Study 2 the spreading of mMBM was estimated to result in infectivity on nonpasture land of 1.62 × 10−8 Bovine Oral ID50/m3. The mean simulated probability of infection per year per bovine animal was 1.11 × 10−9. Given the low infectivity density and corresponding low risks to bovines the spreading of mMBM could be considered a viable alternative for the utilization of mMBM.