TABLE 2.

Oral inoculation of ARQ/VRQ lambs with decreasing amounts of a reference endpoint titrated (IC route in ARQ/VRQ sheep) scrapie isolate^a

Equivalent brain material amount per lamb	No. of ID50 IC units in ARQ/VRQ sheep	Transmission in orally challenged ARQ/VRQ sheep
		No. of affected sheep/total no. of sheep	Incubation period (days) (mean ± SD)
2 g	107.4	10/10	257 ± 18
200 mg	106.4	10/10	279 ± 37
20 mg	105.4	8/8b	305 ± 44
2 mg	104.4	6/9b	545 ± 61
Noninoculated control		0/10	>1,200

^aGroups of 10 ARQ/VRQ lambs were orally challenged with decreasing amounts of a reference scrapie isolate. This isolate had previously been endpoint titrated by the intracerebral route in ARQ/VRQ (Table 1). Lambs were challenged within their first 48 h of life by natural suckling.

^bSome of the challenged animals died from intercurrent disease within the first months of life. At death, to confirm the scrapie infection status, PrP^Sc deposition in lymphoid tissues and central nervous system was assessed in each animal by Western blot analysis.