Prevention of scrapie transmission in sheep, using embryo transfer.
Reciprocal embryo transfers were made between scrapie-inoculated and scrapie-free sheep (Cheviot and Suffolk breeds) to measure scrapie transmission via the embryo (using offspring from embryos of scrapie-inoculated donors and scrapie-free recipients) and via the uterus (using offspring from embryos of scrapie-free donors and scrapie-inoculated recipients taken by cesarean section). Two control groups of offspring, 1 from scrapie-free parents (negative) and 1 from scrapie-inoculated parents (positive), also were included. All sheep were observed for clinical signs of scrapie until death or for a minimum of 60 months. Final diagnosis was made on the basis of histopathologic findings or results of mouse inoculation and/or proteinase-K-resistant protein analysis. Thirty to 61% of the scrapie-inoculated donor/recipient sheep within groups developed scrapie within 8 to 44 months after inoculation. None of the scrapie-free donor/recipients, including those gestating embryos from scrapie-inoculated donors, developed scrapie. Also, none of the offspring observed to > or = 24 months of age from reciprocal cross, via embryo (0/67), or via the uterus (0/25), or from the negative-control group (0/33) developed scrapie. Fifty-six of the offspring via embryo, 19 of these via the uterus, and 31 negative controls survived to > or = 60 months of age. Of the 21 sheep in the positive-control group, 2 (9.5%) developed scrapie, 1 at 31 months of age and 1 at 42 months of age. In the Cheviot offspring, the percentage of sheep carrying the short incubation allele ranged from 24 to 44% and the percentage in the Suffolk offspring ranged from 61 to 83%.(ABSTRACT TRUNCATED AT 250 WORDS)
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Animal, Dairy and Veterinary Sciences Department, Utah State University, Logan 84322-4815.
Clark
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Maciulis
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Call
J W
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Hourrigan
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Evans
R C
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Marshall
M R
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de Camp
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D000818:Animals; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000382:microbiology; D005260:Female; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D011328:Prions / Q000302:isolation & purification; D012608:Scrapie / Q000382:microbiology / Q000517:prevention & control* / Q000635:transmission*; D012756:Sheep; D013997:Time Factors; D014599:Uterus / Q000382:microbiology
D011328:Prions