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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%.