ANALYSIS OF DAM-CALF PAIRS OF BSE CASES - CONFIRMATION OF A MATERNAL RISK ENHANCEMENT

We investigate whether a calf born to a dam that develops bovine spong iform encephalopathy (BSE) (prior or subsequent to the birth) is itsel f at an enhanced risk of developing BSE. Analyses utilize the main dat abase on reported BSE cases in the British cattle herd maintained by t he Central Veterinary Laboratory in Weybridge to trace the darns of BS E-affected animals born following the ruminant feed ban in July 1988. The data reveal a significantly enhanced risk of disease in calves bor n to BSE-affected dams, with the risk being greatest when birth occurs after the onset of clinical signs of disease in the dam. The dependen ce of the maternally enhanced risk on the maternal incubation stage at birth argues for a significant component of direct maternal transmiss ion of the aetiological agent of BSE, and offers little support for th e hypothesis of. genetic predisposition. Using a statistical likelihoo d model, we obtain estimates of the rate of direct maternal transmissi on by maternal incubation stage; however, biases in the available data make these values minimum estimates.