THE MYTH OF MATERNAL TRANSMISSION OF SPONGIFORM ENCEPHALOPATHY

It has long been accepted that the pattern of occurrence of scrapie-th e form of spongiform encephalopathy associated with sheep-is determine d mainly by maternal transmission, and this view has had a profound in fluence on policy decisions in the control of bovine spongiform enceph alopathy and on public concern over the risk to human health from this disease. The occurrence of maternal transmission is, however, not pre dicted by modern knowledge of the aetiology of spongiform encephalopat hy, and even though claims of maternal transmission have been reiterat ed frequently in the literature, re-examination of the source data rev eals that these data are extremely scanty, unreplicated, and probably subject to ascertainment bias. The probability of maternal transmissio n of spongiform encephalopathy in any species should be viewed with th e greatest scepticism.