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Table 1 Performances of six qualification strategies for substantiating scrapie freedom.

From: Comparison of strategies for substantiating freedom from scrapie in a sheep flock

Population Strategy Qualification successes
   Frequency (%) Duration (years)a Diagnostic testsa Genotyping examsa
Susceptible A1 50/50 (100%) 5.8 197 360
  A2 5/50 (10%) 8.8 0 464
  B1 6/50 (12%) 9.7 323 323
  B2 0/50 (0%)    
  C1 50/50 (100%) 5.8 196 138
  C2 0/50 (0%)    
Resistant A1 47/50 (94%) 4.1 140 300
  A2 43/50 (86%) 5.1 0 335
  B1 0/50 (0%)    
  B2 0/50 (0%)    
  C1 47/50 (94%) 4.2 141 106
  C2 19/50 (38%) 8.3 0 186
  1. aMean values when qualification succeeds.
  2. Results obtained in simulated flocks from a susceptible (30% susceptibility alleles and 10% resistance alleles, 50 flocks) and from a resistant population (10% susceptibility alleles and 30% resistance alleles, 50 flocks) according to the qualification strategy: (i) full genotyping with (A1) or without (A2) negative test results for culled animals, (ii) genotyping and negative test result for each culled animal with (B1) or without (B2) known flock pedigree, and (iii) genotyping of founders animals with known flock pedigree with (C1) or without (C2) negative test result for culled animals). The design prevalence is 1%.