Eosinophils play a role in host resistance to gastrointestinal nematodes (GIN) and eosinophil-derived granule proteins (EDGP) are important for host resistance. Previous work indicates that the structures of some EDGP differ across host species, indicating varying functionalities. Predictions of these functions across ruminant species will inform in vitro experiments; directing the development of better control methods. Bioinformatic analyses were used to identify and compare the sequences and structures of eosinophil cationic protein (ECP), eosinophil derived neurotoxin (EDN) and Charcot-Leyden Crystal (CLC) protein orthologues in Bos taurus, Ovis aries and Capra hircus. EDN, ECP and CLC orthologues are present in all three ruminant species. Similar substrate specificities between CLC and its ruminant orthologues (galectin-14) are predicted, given the conservation of the crucial carbohydrate-binding residues His76, Asn90 and Trp97 across proteins. Variations in helminthotoxic activity between EDN orthologues may result from substitutions at catalytic sites His82Phe and His8Tyr. Met35 and Val36 substitutions observed within the critical cell-penetrating peptide (CPP) in ECP orthologues, and heparin-binding region 1 (HBR1) in EDN orthologues suggests reduced cytotoxicity of these proteins. However, the theoretical isoelectric points (pI) of ECP and EDN orthologues are in contrast to this finding, suggesting higher cytotoxicities for sheep, cow and goat EDN proteins, as compared to human EDN, but similar cytotoxicities for ECP orthologues. Consequently, a