Scott,
Thank you very much for your willingness to donate part of your liver. As you know (or will learn), live liver donation has quite a bit more risk to the donor than does live kidney donation. Please discuss all that thoroughly with the transplant center, and a neutral third-party expert (e.g., your primary MD or a gastroenterologist you know or your PMD recommends).
CJD [= Creutzfeldt-Jakob (KROITS-felt YAH-kobe) Disease -- thanks, Mayo Clinic] is a disease caused by "abnormal prion proteins." "vCJD" [= variant CJD] is cause by abnormal prion proteins acquired by eating meat from animals whose brains are infected with the disease and (apparently) some of that brain matter gets into or on the meat -- called "mad cow" disease when in domesticated cattle. (Those cattle get it from eating meal that includes CJD-infected brain matter from other cattle.) There is no blood test that detects presence of the abnormal prion proteins. No case of CJD has ever occurred via donated human blood or blood products. Nevertheless, to be on the safe side, the FDA prohibits blood donations from people who resided in the UK or France since the onset of vCJD there.
Scott, ask the transplant center what its policy is. A policy might include the length of time since you resided there. There is no test any center can do to detect the abnormal prion protein.
All the best, Bill