Studies of the transmissibility of the agent of bovine spongiform encephalopathy to pigs.
Studies to test the transmissibility of the bovine spongiform encephalopathy (BSE) agent to pigs began in 1989. Parenteral inoculation of the agent by three routes simultaneously (intracranially, intravenously and intraperitoneally) produced disease with an incubation period range of 69-150 weeks. Pre-clinical pathological changes were detected in two pigs killed electively at 105 and 106 weeks post-inoculation. Infectivity was detected by bioassay in inbred mice in the CNS of those pigs that developed spongiform encephalopathy. Infectivity was also found in the stomach, jejunum, distal ileum and pancreas of terminally affected pigs. These findings show that pigs are susceptible to BSE. In contrast, disease failed to occur in pigs retained for 7 years after exposure by feeding BSE-affected brain on three separate days, at 1-2 week intervals. The amounts fed each day were equivalent to the maximum daily intake of meat and bone meal in rations for pigs aged 8 weeks. No infectivity was found in tissues assayed from the pigs exposed orally. This included tissues of the alimentary tract. It is suggested that these pigs did not become infected. The relatively high oral exposure used in these experiments compared with feed-borne exposure in the field may explain the absence of an epidemic of spongiform encephalopathy in domestic pigs concurrent with the BSE epidemic in the UK.
Wells
Gerald A H
GAH
Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
Hawkins
Stephen A C
SAC
Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
Austin
Anthony R
AR
FARA, Oak Farm, Harpsden Bottom, Henley-on-Thames, Oxon RG9 4HY, UK.
Ryder
Stephen J
SJ
Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
Done
Stanley H
SH
Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
Green
Robert B
RB
Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
Dexter
Ian
I
Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
Dawson
Michael
M
NSPAC, DEFRA, Whittington Road, Worcester WR5 2SU, UK.
Kimberlin
Richard H
RH
SARDAS, 27 Laverockdale Park, Edinburgh EH13 0QE, UK.
D000818:Animals; D001921:Brain / Q000378:metabolism; D002417:Cattle; D004195:Disease Models, Animal; D018562:Disease Transmission, Infectious; D016643:Encephalopathy, Bovine Spongiform / Q000635:transmission*; D005753:Gastric Mucosa / Q000378:metabolism; D007082:Ileum / Q000378:metabolism; D007583:Jejunum / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D011328:Prions / Q000032:analysis; D013552:Swine; D013553:Swine Diseases / Q000209:etiology*; D013997:Time Factors
D011328:Prions