Western blot of dust sPMCA analysis. All sPMCA reactions at round 9 were analysed by dot blot (Table 1). Dot blot and western blot results were comparable, examples of 4 sample types subject to sPMCA are depicted as western blots. Control area 1 and control area 2 are samples collected from two areas of the scrapie negative control farm. Scrapie barn 1 area 3 and Scrapie barn 2 area 12 correspond to samples named in Table 1. PrPSc was detected using monoclonal antibody SHa31; M are 20 and 30 kDa molecular mass markers.