Transgenic mouse bioassay of CWD in Tg338 and TgElk. Shown are the outcomes for the first intracerebral inoculation of mice with CWD derived from white-tailed deer (WTD804). Closed circles, mice culled at the onset of clinical disease and PrPres detected in the brain; open circles, preclinical mice (culled due to intercurrent health issues, PrPres detected in the brain); open squares, mice with no detectable PrPres in the brain at the time of cull. Censored data are included. Tg338 inoculated with white-tailed deer brain homogenate harbouring CWD prions did not develop clinical disease and had no detectable PrPres in the brain, whereas nearly all TgElk mice similarly inoculated were culled at onset of clinical disease and all had detectable PrPres in the brain.