Estimating the impact on food and edible materials of changing scrapie control measures : the scrapie control model

Multiple controls established during the bovine spongiform encephalopathy (BSE) epidemic were not solely applied to BSE in cattle, but were implemented for scrapie in sheep and goats due to concerns over the occurrence of BSE in sheep. In the absence of BSE in sheep being observed, control measures for prion diseases are now being evaluated to ensure they remain proportionate to risk. This risk assessment, aims to estimate, by use of stochastic simulation, the impact of reducing controls for Specified Risk Materials (SRM) from sheep at abattoir. Three scenarios have been included: 1) current list of SRM; 2) brain and spinal cord of adult sheep; and 3) the brain of adult sheep. Results indicate the total amount of infectivity passing through British abattoirs is highest for atypical scrapie with nearly 3,500,000 Ovine Oral (OO) ID50 per year. The majority of this infectivity enters Category 1 waste for incineration, with only 13,000 OO ID50 per year within edible products. Under Scenario 2, an additional 4,000 OO ID50 per year would be classified as edible products from the lifting of restrictions on the distal ileum of adult sheep. However, if SRM removal was limited to brain, an additional 110,000 OO ID50 per year would be permitted into edible products with the lifting of restrictions on the spinal cord of adult sheep. For classical scrapie, there is a mean estimate of infectivity of 30,000 OO ID50 per year at abattoir. This is lower than for atypical scrapie due to the lower occurrence of this disease in Britain. However, more infectivity is destined to reach the food chain as the disease is peripherally distributed in the carcase. The highest contributor to the total amount of infectivity consumed per year is the intestines (duodenum and jejunum). If SRM removal is limited to the brain and spinal cord of sheep over 12 months of age, there is an approximate mean increase from 19,000 to 21,000 OO ID50 per year diverted to edible products. If the SRM list is restricted to brain only, this increases to over 23,000 OO ID50 per year. For the potential of sheep-BSE, there is a very low estimate of 29 OO ID50 per year in total from carcases entering abattoir, due to the potential very rare occurrence of this disease. Given changes in SRM regulations there is a change of an additional 4 OO ID50 per year being diverted to edible products

Assessing the aggregated probability of entry of a novel prion disease agent into the United Kingdom

In 2018 prion disease was detected in camels at an abattoir in Algeria for the first time. The emergence of prion disease in this species made it prudent to assess the probability of entry of the pathogen into the United Kingdom (UK) from this region. Potentially contaminated products were identified as evidenced by other prion diseases. The aggregated probability of entry of the pathogen was estimated as very high and high for legal milk and cheese imports respectively and very high, high and high for illegal meat, milk and cheese products respectively. This aggregated probability represents a qualitative assessment of the probability of one or more entry events per year into the UK; it gives no indication of the number of entry events per year. The uncertainty associated with these estimates was high due to the unknown variation in prevalence of infection in camels and an uncertain number and type of illegal products entering the UK. Potential public health implications of this pathogen are unknown although there is currently no evidence of zoonotic transmission of prion diseases other than bovine spongiform encephalopathy to humans

A review of cleaning and disinfection guidelines and recommendations following an outbreak of classical scrapie

[EN] Classical scrapie is a prion disease of small ruminants, the infectious agent of which has been shown to be extremely persistent in the environment. Cleaning and disinfection (C&D) after a scrapie outbreak is currently recommended by many governments' veterinary advisors and implemented in most farms affected. Yet, the effectiveness of these procedures remains unclear. The aim of this study was to review existing literature and guidelines regarding farm C&D protocols following classical scrapie outbreaks and assess their effectiveness and the challenges that translation of policy and legislative requirements present at a practical level. A review of the literature was conducted to identify the on-farm C&D protocols used following outbreaks of scrapie, assess those materials with high risk for persistence of the scrapie agent on farms, and review the existing evidence of the effectiveness of recommended C&D protocols. An expert workshop was also organised in Great Britain (GB) to assess: the decision-making process used when implementing C&D protocols on GB farms, the experts' perceptions on the effectiveness of these protocols and changes needed, and their views on potential recommendations for policy and research. Outputs of the literature review revealed that the current recommended protocol for C&D [1 h treatment with sodium hypochlorite containing 20,000 ppm free chlorine or 2 M sodium hydroxide (NaOH)] is based on labo-ratory experiments. Only four field farm experiments have been conducted, indicating a lack of data on effec-tiveness of C&D protocols on farms by the re-occurrence of scrapie infection post re-stocking. Recommendations related to the control of outdoor environment, which are difficult and expensive to implement, vary between countries. The expert workshop concluded that there are no practical, cost-effective C&D alternatives to be considered at this time, with control therefore based on C&D only in combination with additional time restrictions on re-stocking and replacement with non-susceptible livestock or more genetically resistant types, where available. Participants agreed that C&D should still be completed on scrapie affected farms, as it is considered to be "good disease practice" and likely to reduce the levels of the prion protein. Participants felt that any additional protocols developed should not be "too prescriptive" (should not be written down in specific policies) because of significant variation in farm types, farm equipment and installations. Under this scenario, control of classical scrapie on farms should be designed with a level of C&D in combination with re-stocking temporal ban and replacement with livestock of limited susceptibility.The APHA would like to thank all the expert contributions at the workshop. This study was funded by Defra (UK) under Project SE1960 and the Government of education and science of the Generalitat Valenciana (Spain)Alarcon, P.; Marco-Jiménez, F.; Horigan, V.; Ortiz-Pelaez, A.; Rajanayagam, B.; Dryden, A.; Simmons, H.... (2021). A review of cleaning and disinfection guidelines and recommendations following an outbreak of classical scrapie. Preventive Veterinary Medicine. 193:1-9. https://doi.org/10.1016/j.prevetmed.2021.1053881919

A comparison of regulatory and policy aspects for agro-biotech products in the EU and US

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A spatial entry assessment model for incursion of exotic swine diseases into the European Union

The threat of incursion of exotic animal pathogens into the European Union (EU) Member States (MS) via transmission routes such as human travel and trade of live animals and their products is dynamic and needs to be continually re-assessed. Here, we present a quantitative spatial entry assessment model for assessing the risk of incursion of exotic pig diseases such as Classical Swine Fever (CSF) into the EU.</p

Risk analysis of Transmissible Spongiform Encephalopathies in animals: state-of-the-art

International audienceThe Bovine Spongiform Encephalopathy (BSE) crisis of the last two decades has shown that proper interaction of risk assessment, risk management and risk communication is essential. Mathematical models and risk assessments have been used as a basis for BSE risk management options and much of the legislation regarding the control and eradication of BSE. Much uncertainty regarding important input parameters remains a major constraint in risk assessment. Uncertainty is one of the most critical and most difficult aspects of communication of risks about Transmissible Spongiform Encephalopathies (TSEs). Nevertheless, the decline in the BSE epidemic in the UK and most European countries demonstrates that management has been, for the most part, successful. Literature pertaining to the three inter-related facets of risk analysis: risk assessment, risk management and risk communication of TSEs of animal origin was reviewed and used to describe the state-of-the-art of risk analysis for TSEs

Updated quantitative risk assessment (QRA) of the BSE risk posed by processed animal protein (PAP)

EFSA was requested: to assess the impact of a proposed quantitative real-time polymerase chainreaction (qPCR)‘technical zero’on the limit of detection of official controls for constituents of ruminantorigin in feed, to review and update the 2011 QRA, and to estimate the cattle bovine spongiformencephalopathy (BSE) risk posed by the contamination of feed with BSE-infected bovine-derivedprocessed animal protein (PAP), should pig PAP be re-authorised in poultry feed and vice versa, usingboth light microscopy and ruminant qPCR methods, and action limits of 100, 150, 200, 250 and 300DNA copies. The current qPCR cannot discriminate between legitimately added bovine material andunauthorised contamination, or determine if any detected ruminant material is associated with BSEinfectivity. The sensitivity of the surveillance for the detection of material of ruminant origin in feed iscurrently limited due to the heterogeneous distribution of the material, practicalities of sampling andtest performance. A‘technical zero’will further reduce it. The updated model estimated a total BSEinfectivity four times lower than that estimated in 2011, with less than one new case of BSE expectedto arise each year. In the hypothetical scenario of a whole carcass of an infected cow entering the feedchain without any removal of specified risk material (SRM) or reduction of BSE infectivity via rendering,up to four new cases of BSE could be expected at the upper 95th percentile. A second modelestimated that at least half of the feed containing material of ruminant origin will not be detected orremoved from the feed chain, if an interpretation cut-off point of 100 DNA copies or more is applied. Ifthe probability of a contaminated feed sample increased to 5%, with an interpretation cut-off point of300 DNA copies, there would be a fourfold increase in the proportion of all produced feed that is contaminated but not detected.publishedVersio

Updated quantitative risk assessment (QRA) of the BSE risk posed by processed animal protein (PAP)

EFSA was requested: to assess the impact of a proposed quantitative real-time polymerase chainreaction (qPCR)‘technical zero’on the limit of detection of official controls for constituents of ruminantorigin in feed, to review and update the 2011 QRA, and to estimate the cattle bovine spongiformencephalopathy (BSE) risk posed by the contamination of feed with BSE-infected bovine-derivedprocessed animal protein (PAP), should pig PAP be re-authorised in poultry feed and vice versa, usingboth light microscopy and ruminant qPCR methods, and action limits of 100, 150, 200, 250 and 300DNA copies. The current qPCR cannot discriminate between legitimately added bovine material andunauthorised contamination, or determine if any detected ruminant material is associated with BSEinfectivity. The sensitivity of the surveillance for the detection of material of ruminant origin in feed iscurrently limited due to the heterogeneous distribution of the material, practicalities of sampling andtest performance. A‘technical zero’will further reduce it. The updated model estimated a total BSEinfectivity four times lower than that estimated in 2011, with less than one new case of BSE expectedto arise each year. In the hypothetical scenario of a whole carcass of an infected cow entering the feedchain without any removal of specified risk material (SRM) or reduction of BSE infectivity via rendering,up to four new cases of BSE could be expected at the upper 95th percentile. A second modelestimated that at least half of the feed containing material of ruminant origin will not be detected orremoved from the feed chain, if an interpretation cut-off point of 100 DNA copies or more is applied. Ifthe probability of a contaminated feed sample increased to 5%, with an interpretation cut-off point of300 DNA copies, there would be a fourfold increase in the proportion of all produced feed that is contaminated but not detected