That thumb-spike could have been useful for scratching... ;-)
Poinar G. & Boucot, A.J. (2006) Evidence of intestinal parasites of
dinosaurs. Parasitology. 20: 1-5 [Epub ahead of print]
Abstract: "Protozoan cysts and helminth eggs preserved in a
coprolite from the Early Cretaceous Bernissart _Iguanodon_ shaft in
Belgium demonstrate that representatives of 3 phyla parasitized
dinosaurs by that period. These fossil parasite stages are described
and their possible effect on dinosaurs discussed. These findings
represent the earliest fossil records of protozoan and helminth
parasites of terrestrial vertebrates."