Can't say I have found any skeletons while digging, I still reckon that when hit with both myxi and rvhd at the same time what ever immunity they might have can't deal with both diseases.
The past few summers I have watched good numbers in various burys, only to return in winter with nets and ferrets and catch 1 or 2.
These diseases seem to strike when population is at its highest, I guess when the fleas are most prolific?