A simple save/reload did not work for me. I even went to Skellige, saved. Quit the game, loaded the save. Went back and still no ghouls.
Seems this didn't get fixed for 1.10, unfortunately: http://wpc.4d7d.edgecastcdn.net/004D7D/media/THE%20WITCHER%203/Pdf/patch_1_10_changelog_en.pdf
Oh, well...