NR ARXP
AU Wilesmith,J.W.; Ryan,J.B.M.
TI J.W. Wilesmith and J.B. Ryan comment on Donnelly
QU The Veterinary Record 1998 May 23; 142(21): 580
PT Kommentar
VT
J.W. Wilesmith and J.B. Ryan comment: We should perhaps point out that Dr Donnelly is not correct in saying that we did not take account of the observed incubation period and that the expected number of cases assuming 10 per cent transmission throughout the incubation period, using Dr Donnelly's method, is 7.3, which is consistent with our estimate of 7. However, we do not feel that Dr Donnelly's results materially affect the conclusion drawn from the results of our analyses.
Our conclusion was related to the estimation of the true risk for offspring of BSE-affected dams. As there were no cases of BSE in the offspring of the BSE-affected suckler cows we simply suggested that risk from the cohort study (Wilesmith and others 1997) and the confidence intervals are larger. Therefore, it is not possible to determine whether the transmission rates are different in these two studies. We feel, therefore, that there is an overemphasis of the upper 95 per cent confidence interval from Dr Donnelly's analysis, when both studies are also consistent with much lower rates.
The refinement of the estimate of the true risk for offspring is important. The potential risk of maternal transmission is a key factor in assessing risks to the public's health in terms of making potential changes to the current control measures, particularly those related to international trade of bovines and bovine products. As a result, we are currently in the process of conducting a further follow-up of the relevant animals and herds in this study. The results of this will be reported in the usual way, as will those from further analyses of the cohort study which attempt to take account of the confounding effect of the feed borne source.
J.W. Wilesmith, J. B. Ryan, Epidemiology Department, Central Veterinary Laboratory, New Haw, Addlestone, Surrev KTI5 3N3
References
WILESMITH, J. W. & RYAN, J. B. M. (1997) Veterinary Record 141, 250
WILESMITH, J. W., WELLS, 0. A. Hi, RYAN, Ji B. Mi, GAVIER-WIDEN. D. & SIMMONS. M. M. (1997) Veterinary Record 141,239
AD J.W. Wilesmith, J. B. Ryan, Epidemiology Department, Central Veterinary Laboratory, New Haw, Addlestone, Surrev KTI5 3N3
SP englisch
PO England
OR Prion-Krankheiten 8