Scrapie prevalence in sheep of susceptible genotype is declining in a population subject to breeding for resistance

Table 8 Relative scrapie risks

Culled flocks				British cases (1998-2002)
Genotype	Cases (Total tested)	Cases/1000	Relative risk (Confidence bounds)	Relative risk calculated from Ref. [7]
ARR/ARR	0 (237)	0.0	0.0 (0.0 -0.03)	0.00
ARR/AHQ	0 (26)	0.0	0.0 (0.0 -0.26)	0.00
ARR/ARQ*	0 (409)	0.0	0.0 (0.0 -0.02)	0.00
ARR/VRQ	24 (875)	27.4	0.10 (0.06-0.15)	0.03
AHQ/AHQ	0 (32)	0.0	0.0 (0.0 -0.21)	0.02
AHQ/ARQ*	1 (192)	5.2	0.02 (0.001-0.08)	0.04
AHQ/VRQ	2 (26)	76.9	0.27 (0.05-0.79)	0.00
ARQ/ARQ	54 (1882)	28.7	0.10 (0.08-0.14)	0.13
ARQ*/VRQ	155 (553)	280.3	1.00 (1.00-1.00)	1.00
VRQ/VRQ	21 (57)	368.4	1.31 (0.88-1.83)	2.33

Cases found in different genotypes (including index case) in culled flocks, cases per 1000 animals of given genotype, and relative case risk r_γof the different genotypes (setting the risk of ARQ*/VRQ equal to unity). Comparison to the relative risks of death from scrapie in British sheep estimated by Baylis et al. [7]. The total number of cases in this Table is 257; three remaining cases were in animals for which the genotype could not be determined.

ISSN: 1746-6148