Classical and Atypical Scrapie in Sheep and Goats. Review on the Etiology, Genetic Factors, Pathogenesis, Diagnosis, and Control Measures of Both Diseases

Acín, Cristina; Bolea, Rosa; Monzón, Marta; Monleón, Eva; Moreno, Bernardino; Filali, Hicham; Marín, Belén; Sola, Diego; Betancor, Marina; Guijarro, Isabel M; García, Mirta Lidia; Vargas, Antonia; Badiola, Juan José

doi:10.3390/ani11030691

Cited by 20 publications

(21 citation statements)

References 170 publications

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“…Furthermore, codon 146D could also be included in these inventory studies [ 38 ]. Therefore, choosing regional suitable alleles for resistance breeding against scrapie in goats remains a challenging research area [ 40 , 54 , 55 ]. Several actions need to be taken at this stage in Greece to accomplish a scrapie-resistant goat population, namely (i) to produce regional polymorphism inventories for areas of Greece not yet explored, (ii) further case-control studies, (iii) challenge experiments in transgenic mice with Greek isolates to confirm the quality of the 222K allele for resistance breeding, and (iv) organizing breeding centers for 146D, 146S, 110P, and 222K goats.…”

Section: Discussionmentioning

confidence: 99%

Polymorphisms of Codons 110, 146, 211 and 222 at the Goat PRNP Locus and Their Association with Scrapie in Greece

Gelasakis

Boukouvala²,

Babetsa³

et al. 2021

Animals

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Scrapie is considered an endemic disease in both sheep and goats in Greece. However, contrary to sheep, in goats more than one prion protein (PrP) polymorphism has been recognized as a candidate for resistance breeding against the disease. For an impression, candidates which are circulating, (i) brain samples (n = 525) from scrapie-affected (n = 282) and non-affected (n = 243) animals within the national surveillance program, and (ii) individual blood samples (n = 1708) from affected (n = 241) and non-affected (n = 1467) herds, in a large part of mainland Greece and its islands, were collected and assayed. A dedicated Taqman method was used to test for amino acid polymorphisms 110T/P, 146N/S/D, 211R/Q, and 222Q/K. Highly prevalent genotypes were 110TT, 146NN, 211RR, and 222QQ. The frequencies of polymorphisms in blood and negative brain samples for codons 110P, 211Q, and 222K were 4.0%, 3.0%, and 1.9%, respectively, while 146D (0.7%) was present only on Karpathos island. Codon 110P was exclusively found in scrapie-negative brains, and homozygous 110P/P in two scrapie-negative goats. It is concluded that breeding programs in Karpathos could focus on codon 146D, while in other regions carriers of the 110P and 222K allele should be sought. Case-control and challenge studies are now necessary to elucidate the most efficient breeding strategies.

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Section: Discussionmentioning

confidence: 99%

Polymorphisms of Codons 110, 146, 211 and 222 at the Goat PRNP Locus and Their Association with Scrapie in Greece

Gelasakis

Boukouvala²,

Babetsa³

et al. 2021

Animals

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“…However, the atypical form of scrapie (Nor98) could occur in sheep that are resistant to typical scrapie [ 23 ]. However, Nor98 scrapie type is believed to be a spontaneous disease and it is unlike to be naturally contagious among sheep and, thus, its prevalence is low [ 24 , 25 ]. Therefore, a well-established breeding program for the typical scrapie can contribute to the reduction of scrapie prevalence.…”

Section: Discussionmentioning

confidence: 99%

Prediction of Genetic Resistance for Scrapie in Ungenotyped Sheep Using a Linear Animal Model

Boareki

Schenkel

Kennedy

et al. 2021

Genes

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Selection based on scrapie genotypes could improve the genetic resistance for scrapie in sheep. However, in practice, few animals are genotyped. The objectives were to define numerical values of scrapie resistance genotypes and adjust for their non-additive genetic effect; evaluate prediction accuracy of ungenotyped animals using linear animal model; and predict and assess selection response based on estimated breeding values (EBV) of ungenotyped animals. The scrapie resistance (SR) was defined by ranking scrapie genotypes from low (0) to high (4) resistance based on genotype risk groups and was also adjusted for non-additive genetic effect of the haplotypes. Genotypes were simulated for 1,671,890 animals from pedigree. The simulated alleles were assigned to scrapie haplotypes in two scenarios of high (SRh) and low (SRl) resistance populations. A sample of 20,000 genotyped animals were used to predict ungenotyped using animal model. Prediction accuracies for ungenotyped animals for SRh and SRl were 0.60 and 0.54, and for allele content were from 0.41 to 0.71, respectively. Response to selection on SRh and SRl increased SR by 0.52 and 0.28, and on allele content from 0.13 to 0.50, respectively. In addition, the selected animals had large proportion of homozygous for the favorable haplotypes. Thus, pre-selection prior to genotyping could reduce genotyping costs for breeding programs. Using a linear animal model to predict SR makes better use of available information for the breeding programs.

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“…AS is different from CS regarding its clinical presentation, but also in its molecular characteristics, the anatomical distribution of PrP Sc within infected sheep, the genotypes affected and its epidemiology (see Greenlee, 2019 , for recent review). Whereas more than 20 different strains of CS have been described, only one has been demonstrated in AS so far (Acín et al., 2021 ). AS was reported for the first time in Norway in 1998 (Benestad et al., 2003 , 2008 ), although later retrospective studies have confirmed its presence in a small number of surveillance cases in the UK from before that date (Bruce et al., 2007 ; Webb et al., 2009 ).…”

Section: Assessmentmentioning

confidence: 99%

Scientific report on the analysis of the 2‐year compulsory intensified monitoring of atypical scrapie

Arnold¹,

Ru²,

Simmons³

et al. 2021

EFS2

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The European Commission asked EFSA whether the scientific data on the 2-year intensified monitoring in atypical scrapie (AS) outbreaks (2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020) provide any evidence on the contagiousness of AS, and whether they added any new knowledge on the epidemiology of AS. An ad hoc data set from intensified monitoring in 22 countries with index case/s of AS in sheep and/or goats (742 flocks from 20 countries, 76 herds from 11 countries) was analysed. No secondary cases were confirmed in goat herds, while 35 secondary cases were confirmed in 28 sheep flocks from eight countries. The results of the calculated design prevalence and of a model simulation indicated that the intensified monitoring had limited ability to detect AS, with no difference between countries with or without secondary cases. A regression model showed an increased, but not statistically significant, prevalence (adjusted by surveillance stream) of secondary cases in infected flocks compared with that of index cases in the non-infected flocks (general population). A simulation model of within-flock transmission, comparing a contagious (i.e. transmissible between animals under natural conditions) with a non-contagious scenario, produced a better fit of the observed data with the non-contagious scenario, in which each sheep in a flock had the same probability of developing AS in the first year of life. Based on the analyses performed, and considering uncertainties and data limitations, it was concluded that there is no new evidence that AS can be transmitted between animals under natural conditions, and it is considered more likely (subjective probability range 50-66%) that AS is a non-contagious, rather than a contagious disease. The analysis of the data of the EU intensified monitoring in atypical scrapie infected flocks/herds confirmed some of the known epidemiological features of AS but identified that major knowledge gaps still remain.

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Classical and Atypical Scrapie in Sheep and Goats. Review on the Etiology, Genetic Factors, Pathogenesis, Diagnosis, and Control Measures of Both Diseases

Cited by 20 publications

References 170 publications

Polymorphisms of Codons 110, 146, 211 and 222 at the Goat PRNP Locus and Their Association with Scrapie in Greece

Polymorphisms of Codons 110, 146, 211 and 222 at the Goat PRNP Locus and Their Association with Scrapie in Greece

Prediction of Genetic Resistance for Scrapie in Ungenotyped Sheep Using a Linear Animal Model

Scientific report on the analysis of the 2‐year compulsory intensified monitoring of atypical scrapie

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