Dynamics of the natural transmission of bovine spongiform encephalopathy within an intensively managed sheep flock

Jeffrey, Martin; Witz, Janey P.; Martin, Stuart; Hawkins, Steve A. C.; Bellworthy, Sue J.; Dexter, Glenda E.; Thurston, Lisa; González, Lorenzo

doi:10.1186/s13567-015-0269-x

Veterinary Research

Table 1 Details of the study design and results (attack rates and survival times).

From: Dynamics of the natural transmission of bovine spongiform encephalopathy within an intensively managed sheep flock

Type of exposure	Breed and genotype^a	Age at exposure^b	BSE infected			Survivors
Type of exposure	Breed and genotype^a	Age at exposure^b	n	AR	ST	n	ST
Oral challenge	Suffolk ARQ 1 g	9 ± 1	6 ^c	100	575 ± 87 (525–729)	0
	Suffolk ARQ 5 g	112–147	13	100	712 ± 119 (575–1034)	0
		190–255	4	100	712 ± 106 (570–800)	0
		145 ± 41	17	100	712 ± 113	0
	Romney ARQ 5 g	230–253	21	87.5	830 ± 93 (665–1058)	3	2380 (2347–2397)
		342–363	26	92.9	822 ± 149 (672–1365)	2	1580 (1562–1597)
		304 ± 58	47	90.4	825 ± 126	5
	Cheviot VRQ 5 g	54–58	2^d	33.3	966–967	4^d	954 (915–967)
	Cheviot VRQ 5 g	126 ± 0	4	100	1772 ± 206 (1558–2026)	0
	Cheviot AHQ 5 g	76–138	19	100	601 ± 54 (498–665)	0
		229–294	9	100	597 ± 57 (524–686)	0
		145 ± 80	28	100	600 ± 54	0
Total oral dosing			104	92.0		9
F1/infected dam	Suffolk ARQ	From birth	5	27.8	787 ± 101 (654–893)	13	1096 (535–2647)
	Romney ARQ	“	7	16.7	870 ± 154 (673–1084)	35	2020 (693–2674)
	Cheviot VRQ	“	2	11.8	1804, 1883^e	15	1913 (1454–2247)
	Cheviot AHQ	“	0	0		1	1276
F2/infected F1	Romney ARQ	“	0	0		1	1220
Total maternal			14	17.7		65
F1/not infected dam	Suffolk ARQ	From birth	0	0		10	999 (315–2662)
F1/not infected dam	Romney ARQ	“	0	0		20	1116 (309–2621)
F2/not infected F1	Suffolk ARQ	“	0	0		9	997 (312–1580)
F2/not infected F1	Romney ARQ	“	1	2.4	392^e	40	1057 (309–2242)
Sentinels	Suffolk ARQ	From mixing	0	0		12	1614 (1277–1736)
	Romney ARQ	“	0	0		30	2177 (1058–2959)
	Cheviot VRQ	“	0	0		9	1526 (1203–1653)
	Cheviot AHQ	“	0	0		7	1491 (695–1764)
F1–F2/sentinels	Suffolk ARQ	From birth	0	0		19	1034 (293–2243)
	Romney ARQ	“	0	0		42	1559 (344–2621)
	Cheviot VRQ	“	0	0		4	1018 (728–1840)
	Cheviot AHQ	“	0	0		2	403 (298–507)
Total horizontal			1	0.5		204

n, number of sheep in each subgroup and group; AR, attack rate as percentage; ST, survival time in days as mean ± SD (range) for BSE infected sheep (actual days for the two F1 VRQ Cheviot sheep) and as mean (range) for survivors
^aOnly M₁₁₂M ARQ Suffolk sheep included
^bAge at exposure in days as range for the different subgroups and as mean ± SD for the breed/genotype/dose groups (rows in italics; in the case of orally dosed Cheviot VRQ, only those left to develop clinical disease are highlighted)
^cIncludes one BSE +ve animal culled at 371 dpi (not considered in ST values)
^dThese six sheep were culled at preclinical stage
^eThese two sheep were culled at the stated ages in the absence of clinical disease and found to be PrP^d positive

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ISSN: 1297-9716

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