Eddie alerted to the key fob contaminated with cellular material later identified as Gerry McCann's, while it was in the hire vehicle ... that the alert was to the key fob was confirmed by removing it from the vehicle whereupon the dog sought it out and alerted again.
Similarly Keela sought the key fob contaminated with cellular material and alerted to it. What does that tell you?
One explanation is that Keela was trained on the individual components of blood ie, red cells, white cells. plasma & platelets. I've no clue as to how an individual component could leave the human body on its own, although the red blood cells carry no DNA.
ETA Nuclear DNA is only found in nucleated cells — this rules out three of the four major components of blood: red blood cells (which don't have nuclei), platelets and plasma. So you only get nuclear DNA in white blood cells, which are outnumbered by red blood cells in the blood stream by about 600 to one.