NR AMTC
AU Wrathall,A.E.; Brown,K.F.D.; Sayers,A.R.; Wells,G.A.H.; Simmons,M.M.; Farrelly,S.S.J.; Bellerby,P.J.; Squirrell,J.; Spencer,Y.I.; Wells,M.; Stack,M.J.; Bastiman,B.; Pullar,D.; Scatcherd,J.; Heasman,L.; Parker,J.; Hannam,D.A.; Helliwell,D.W.; Chree,A.; Fraser,H.
TI Studies of embryo transfer from cattle clinically affected by bovine spongiform encephalopathy (BSE)
QU The Veterinary Record 2002 Mar 23; 150(12): 365-78
PT journal article
AB Semen from 13 bulls, eight with clinical bovine spongiform encephalopathy (BSE), was used to artificially inseminate (AI) 167 cows with clinical BSE, and their resultant embryos were collected non-surgically seven days after AI. The viable and non-viable embryos with intact zonae pellucidae were washed 10 times (as recommended by the International Embryo Transfer Society) then frozen. Later, 587 of the viable embryos were transferred singly into 347 recipient heifers imported from New Zealand, and 266 live offspring were born of which 54.1 per cent had a BSE-positive sire and a BSE-positive dam. The recipients were monitored for clinical signs of BSE for seven years after the transfer, and the offspring were monitored for seven years after birth. Twenty-seven of the recipients and 20 offspring died while being monitored but none showed signs of BSE. Their brains, and the brains of the recipients and offspring killed after seven years, were examined for BSE by histopathology, PrP immunohistochemistry, and by electron microscopy for scrapie-associated fibrils. They were all negative. In addition, 1020 non-viable embryos were sonicated and injected intracerebrally into susceptible mice (20 embryos per mouse) which were monitored for up to 700 days, after which their brains were examined for spongiform lesions. They were all negative. It is concluded that embryos are unlikely to carry BSE infectivity even if they have been collected at the end-stage of the disease, when the risk of maternal transmission is believed to be highest.
IN Die Autoren liefern die Ergebnisse einer bereits 1991 begonnenen Studie [AVOJ,AVOI]. Von den im Alter von 7 Tagen als Embryonen aus den Uteri ihrer BSE-kranken Mütter heraus gespülten, zehnfach gewaschenen, eingefrorenen und einzeln in neuseeländische Färsen implantierten Rindern überlebten schließlich 266, von denen 54,1% auch BSE-kranke Väter hatten. Die Empfängerkühe wurden vom Zeitpunkt des Transfers, die Kälber vom Zeitpunkt der Geburt an über 7 Jahre beobachtet. In diesen Zeiträumen starben 27 Empfängerkühe und 20 der Nachkommen, aber in keinem Fall gab es Anzeichen für BSE. Nach Ablauf der 7 Jahre wurden alle noch lebenden Tiere getötet und histopathologisch, immunhistochemisch und elektronenmikroskopisch untersucht, aber in keinem Fall wurde BSE festgestellt. Damit verliefen die Rinder-Bioassays ebenso negativ wie die Maus-Bioassays, die auch für die 1020 nicht implantierten Embryonen bei einem Beobachtungszeitraum von 700 Tagen keine BSE-Infektiosität nachweisen konnten.
MH Animal; Biological Assay; Brain/pathology; Cattle; Embryo Transfer/*veterinary; Embryo and Fetal Development; Encephalopathy, Bovine Spongiform/*transmission; Female; Genetic Predisposition to Disease; Genotype; Male; Mice; Risk Assessment; Support, Non-U.S. Gov't
AD Veterinary Laboratories Agency-Weybridge, Addlestone, Surrey.
SP englisch
PO England