Scientific Opinion on the scrapie situation in the EU after 10 years of monitoring and control in sheep and goats

Hald, Tine; Baggesen, Dorte Lau

doi:10.2903/j.efsa.2014.3781

Cited by 54 publications

(36 citation statements)

References 144 publications

(176 reference statements)

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“…There is a paucity of relevant data related to CS dissemination in sheep of other genotypes. However, the data that do exist indicate that in other genotypes the dissemination kinetics of the PrP Sc is slower, and in some cases there is also no LRS involvement (EFSA BIOHAZ Panel, 2010, 2014. Any brainstem samples from animals infected for less than a year are therefore likely to test negative.…”

Section: Parameters Common To All Msmentioning

confidence: 91%

Evaluation of the application of Denmark to be recognised as having a negligible risk of classical scrapie

2015

EFS2

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Denmark submitted a request to the European Commission to be recognised as a Member State with negligible risk of classical scrapie. EFSA has been asked to assess if Denmark in its application has demonstrated for a period of at least seven years proposed/in the future, that a sufficient number of ovine and caprine animals over 18 months of age, representative of slaughtered, culled or found dead on farm animals, have been tested annually, to provide a 95% level of confidence of detecting classical scrapie if it is present in that population at a prevalence rate exceeding 0.1%. A risk-based approach using scenario tree modelling with stochastic simulations was applied. There is lack of data on the actual performance of the approved tests in field conditions, especially in sheep. Alternative scenarios were explored extending the range from the sensitivity provided by the past European Union evaluations of screening diagnostic tests to a sensitivity of 50%, consistent with published data obtained under field conditions in infected goat populations. Using data provided by Denmark in its application, the estimated parameters of the scenario tree model and the range of values of sensitivity, it is concluded that Denmark has not tested annually a sufficient number of small ruminants to meet the requirement. Based on the expected number of samples to be tested in 2015 and future years, Denmark would not test a sufficient number of animals to meet the requirement. It is recommended that specific analytical approaches should be agreed upon for use by other Member States when preparing their applications for the recognition of the negligible risk of classical scrapie, and that data on the sensitivity of screening diagnostic tests in field conditions should be generated where possible.

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Section: Parameters Common To All Msmentioning

confidence: 91%

Evaluation of the application of Denmark to be recognised as having a negligible risk of classical scrapie

2015

EFS2

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“…We estimated the potential evolution of goat PRNP genotypes using a deterministic model, as previously proposed by the EFSA [22] and Roden [23] to monitor the effectiveness of sheep breeding programmes for resistance to classical scrapie. It was assumed that the resistance-associated allele was dominant and that KK and KQ animals showed almost identical resistance; nevertheless, KK bucks were ultimately preferred.…”

Section: Methodsmentioning

confidence: 99%

Predicting the impact of selection for scrapie resistance on PRNP genotype frequencies in goats

Sacchi

Rasero

et al. 2018

Vet Res

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The European Union has implemented breeding programmes to increase scrapie resistance in sheep. A similar approach can be applied also in goats since the K222 allele provides a level of resistance equivalent to that of ARR in sheep. The European Food Safety Authority stated that breeding for resistance could be offered as an option for Member States to control classical scrapie in goats. We assessed the impact of different breeding strategies on PRNP genotype frequencies using a mathematical model that describes in detail the evolution of K222 in two goat breeds, Chamois Coloured and Saanen. Different patterns of age structure and replacement rate were modelled as factors affecting response to selection. Breeding for scrapie resistance can be implemented in goats, even though the initial K222 frequencies in these breeds are not particularly favourable and the rate at which the resistant animals increase, both breeding and slaughtered for meat production, is slow. If the goal is not to achieve the fixation of resistance allele, it is advisable to carry out selection only until a desired frequency of K222-carriers has been attained. Nucleus selection vs. selection on the overall populations is less expensive but takes longer to reach the desired output. The programme performed on the two goat breeds serves as a model of the response the selection could have in other breeds that show different initial frequencies and population structure. In this respect, the model has a general applicability.Electronic supplementary materialThe online version of this article (10.1186/s13567-018-0518-x) contains supplementary material, which is available to authorized users.

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Section: Parameters Common To All Msmentioning

confidence: 99%

Evaluation of the application of Sweden to be recognised as having a negligible risk of classical scrapie

2015

EFS2

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Sweden submitted a request to the European Commission to be recognised as a Member State with negligible risk of classical scrapie. EFSA has been asked to assess if Sweden in its application has demonstrated for a period of at least seven years proposed/in the future, that a sufficient number of ovine and caprine animals over 18 months of age, representative of slaughtered, culled or found dead on farm animals, have been tested annually, to provide a 95% level of confidence of detecting classical scrapie if it is present in that population at a prevalence rate exceeding 0.1%. A risk-based approach using scenario-tree modelling with stochastic simulations was applied. There is lack of data on the actual performance of the approved tests in field conditions, especially in sheep. Alternative scenarios were explored extending the range from the sensitivity provided by the past European Union evaluations of screening diagnostic tests to a sensitivity of 50%, consistent with published data obtained under field conditions in infected goat populations. Using data provided by Sweden in its application, the estimated parameters of the scenario-tree model and the range of values of sensitivity, it is concluded that Sweden has tested annually a sufficient number of small ruminants to meet the requirement. Based on the expected number of samples to be tested in 2015 and future years, Sweden would test a sufficient number of animals to meet the requirement if the actual test sensitivity under field conditions was higher than 80%. It is recommended that specific analytical approaches should be agreed upon for use by other MS when preparing their applications for the recognition of the negligible risk of classical scrapie, and that data on the sensitivity of screening diagnostic tests in field conditions should be generated where possible.

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Scientific Opinion on the scrapie situation in the EU after 10 years of monitoring and control in sheep and goats

Cited by 54 publications

References 144 publications

Evaluation of the application of Denmark to be recognised as having a negligible risk of classical scrapie

Evaluation of the application of Denmark to be recognised as having a negligible risk of classical scrapie

Predicting the impact of selection for scrapie resistance on PRNP genotype frequencies in goats

Evaluation of the application of Sweden to be recognised as having a negligible risk of classical scrapie

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