[Where does BSE in the Netherlands come from?].

It is only in the last 5 years that the Netherlands has been confronted with cases of bovine spongiform encephalopathy (BSE). The cases diagnosed to date have not been clearly linked to imports from the United Kingdom. This article describes the various possible explanations for the Dutch cases. The risk factors involved, have either a connection with imported BSE, local origin of BSE, or both. These factors can also be divided into introductory risk and propagation risk, terms that were also used in an EU risk assessment study. Research at ID-Lelystad since the early 1990s and at IKC-Ede has tried to assess the relative importance of the various risk factors, the results of which are discussed in this paper. The paper does not deal with the specifics of the cases diagnosed to date, because of the absence of an in-depth epidemiological investigation, but provides a general assessment of the risk factors that might have played a role. Important factors have been, in addition to the initial imports of cattle and meat and bone-meal from the UK, the continuing imports from other countries with covert BSE and the cross-contamination within the animal feed production lines. Emphasis is on the period of the early and mid-1990s, the period in which most calves with diagnosed BSE were born.