Bovine Spongiform Encephalopathy Maternal Cohort Study-Exploratory Analysis

The bovine spongiform encephalopathy (BSE) maternal cohort study supports a role both for direct maternal transmission and for inherited genetic susceptibility to the BSE agent. Additional data from the main BSE database do not resolve whether the risk of direct maternal transmission of BSE from dam to calf is concentrated in the interval within 5 months before the onset of BSE in the dam, as data from the BSE maternal cohort study suggest. The reason for this is that we cannot rely, as our analysis requires, on the survival of calves or traceability of the dam being independent of the interval from the birth of a calf to onset of BSE in the dam. Accordingly, for the present, we place most weight on evidence from the BSE maternal cohort study. Direct maternal transmission of the BSE agent from dam to calf has not been ruled out; vertical transmission of the new variant Creutzfeldt-Jakob disease (NVCJD) from mother with NVCJD to baby is therefore also possible. Actions to quantify, and minimize, the transmission risk, if any, from a mother with NVCJD to her baby, or to delivery teams, should be taken without delay.