Estimation of the age-dependent risk of infection to BSE of dairy cattle in Great Britain.
An important aspect of the bovine spongiform encephalopathy (BSE) epidemic has been an apparent age-dependent risk of infection, with younger cattle being more likely to become infected than older cattle. Our objective was to determine the age-dependent risk of infection of dairy cattle. We first reviewed unpublished data on the feeding patterns of proprietary concentrates for dairy-replacement cattle. These data showed that autumn- and spring-born cattle would receive different feeding patterns of proprietary concentrates, and so age-dependent risk of infection profiles were obtained separately for autumn- and spring-born cattle. We used back-calculation methods to analyse BSE-epidemic data collected in Great Britain between 1984 and 1996. Dairy cattle were most at risk in the first 6 months of life; adult cattle were at relatively low risk of infection. Between 6 and 24 months of age, risk profiles reflected feeding patterns of proprietary concentrates in each of the autumn- and spring-born cohorts.
Arnold
M E
ME
Centre for Epidemiology and Risk Analysis, VLA, New Haw, Addlestone, Surrey KT15 3NB, UK. m.arnold@vla.defra.gsi.gov.uk
Wilesmith
J W
JW
D000367:Age Factors; D000821:Animal Feed; D000818:Animals; D002417:Cattle; D003612:Dairying; D016643:Encephalopathy, Bovine Spongiform / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D012307:Risk Factors; D012621:Seasons; D006113:United Kingdom / Q000453:epidemiology