Figure 3. The effect of temperature on the desorption and persistence of PrPTSE on a sandy loam soil over 18 mo. Scrapie (A, B, E, F) or BSE (C, D) prion was incubated on soil at distinct temperatures as indicated. Samples were taken for analysis at 1–4 d, day 188, 411 and 566. Thermolysin-resistant prion was extracted in triplicate (A-D) or singles (E,F) and the eluates from 100 mg of soil analyzed by ELISA, each in triplicate (A-D) or singles (E,F). Analyses detected full length PrPTSE (A-D) or both full length and truncated conformers (E,F). In order to determine the persistence of PrPTSE under different conditions, recoveries at later time points are expressed as a percentage of that extracted at the earliest time point (1- 4 d); therefore adjusting recoveries at these time-points for the effects of temperature on the efficiency of desorption of the prion from the soil (A, C, E). The actual recoveries of PrPTSE for each time-point under the distinct temperatures are also shown (B, D, F). Standard deviations of the nine replicate analyses of each column are shown (A-D). Each set of nine replicates were compared by an unpaired, two-tailed Student's t-test: comparison of each data set to the recovery of PrPTSE at 4°C (* indicates p values < 0.001 or the value is given), or comparison of each data set to PrPTSE recovery at 8–12°C (# indicates p values < 0.001 or the value is given).