Epidemiology of scrapie and Bovine Spongiform Encephalopathy in France

Abstract

After providing an up-to-date overview on our knowledge concerning the infection sources and the transmission routes of Transmissible Spongiform Encephalopathies (TSE), this paper presents a variety of studies carried out at INRA on the resistance of the agent, the infection sources, the transmission routes and the disease dynamic, both for scrapie and Bovine Spongiform Encephalopathy (BSE). These studies involve various national and international collaborations, within French and European projects. Three different approaches were followed. Experimental studies were done on the persistence and dispersion of the prion protein in the soil, as well as on the effect of nematode worms as a possible way of transmission between animals. Epidemiological studies were carried out on the transmission routes of scrapie, concerning rodents, hay mites, worms, husbandry aspects, and the transmission of BSE, focused on feeding. Finally, different mathematical models based on field data simulate the long-term dynamics of scrapie and BSE depending on various scenarios, and allow testing some hypotheses on infection sources. The insets provide more details on these studies.