Figure 4. The effect of temperature on the desorption and persistence of PrPTSE on a sandy loam soil over 18 mo. Scrapie or BSE (as indicated) prion was incubated on soil and samples were analyzed at days1–4, 49, 188, 411 and 566 (Lanes 1 to 5, respectively). Thermolysin-resistant prion was extracted and 10µl analyzed (equivalent of an extract from 100 mg of soil) by western blot. Prion was detected with monoclonal antibody SHa31 (detecting a 'core' epitope) and molecular mass markers are shown (M; 20, 30 and 40kDa).