title: Bovine spongiform encephalopathy: the effect of oral exposure dose on attack rate and incubation period in cattle.
abstract: The dose-response of cattle exposed to the bovine spongiform encephalopathy (BSE) agent is an important component of modelling exposure risks for animals and humans and thereby, the modulation of surveillance and control strategies for BSE. In two experiments calves were dosed orally with a range of amounts of a pool of brainstems from BSE-affected cattle. Infectivity in the pool was determined by end-point titration in mice. Recipient cattle were monitored for clinical disease and, from the incidence of pathologically confirmed cases and their incubation periods (IPs), the attack rate and IP distribution according to dose were estimated. The dose at which 50 % of cattle would be clinically affected was estimated at 0.20 g brain material used in the experiment, with 95 % confidence intervals of 0.04-1.00 g. The IP was highly variable across all dose groups and followed a log-normal distribution, with decreasing mean as dose increased. There was no evidence of a threshold dose at which the probability of infection became vanishingly small, with 1/15 (7 %) of animals affected at the lowest dose (1 mg).
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: G A H
authors: GAH
authors: Wells
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: T
authors: T
authors: Konold
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: M E
authors: ME
authors: Arnold
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: A R
authors: AR
authors: Austin
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: S A C
authors: SAC
authors: Hawkins
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: M
authors: M
authors: Stack
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: M M
authors: MM
authors: Simmons
authors: National Veterinary Research and Quarantine Service, Anyang, Republic of Korea.
authors: Y H
authors: YH
authors: Lee
authors: National Veterinary Institute (SVA), SE-75189 Uppsala, Sweden.
authors: D
authors: D
authors: Gavier-Widén
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: M
authors: M
authors: Dawson
authors: Veterinary Laboratories Agency, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors: J W
authors: JW
authors: Wilesmith
mesh_terms: D000818:Animals; D002417:Cattle; D016643:Encephalopathy, Bovine Spongiform / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology / Q000635:transmission*; D013997:Time Factors