Current copro-diagnostic tests for Anoplocephala perfoliata show high variation in their sensitivity and given the morphological similarity of Anoplocephala spp. eggs, this could be related to the presence of Anoplocephala magna alone or co-existing with A. perfoliata. In the present study, coprology was significantly more sensitive (p0.01) at detecting A. magna than A. perfoliata. This difference was independent of the parasite burden and was greater when testing was limited to horses with mature or gravid tapeworms. A. magna infection was strongly linked to young horses (≤ 2 years). The eggs of A. magna are smaller. Using 15 and 70 μm cut-offs for oncosphere diameter and the major shell bisector length, respectively, the eggs of A. perfoliata were identified with 100% sensitivity, 97% specificity and 98% sensitivity, 84% specificity. The use of these two morphometric variables would therefore be useful for the copro-identification of A. perfoliata in countries where both species coexist.
