Immature common threshers fall prey to larger sharks. Aside from observations of killer whales feeding on common threshers off New Zealand,[21] adults have no known natural predators. Parasites documented from the common thresher include the protozoan Giardia intestinalis,[22] the trematodes Campula oblonga (not usual host)[23] and Paronatrema vaginicola,[24] the tapeworms Acanthobothrium coronatum,[25] Anthobothrium laciniatum,[26] Crossobothrium angustum,[27] Hepatoxylon trichiuri, Molicola uncinatus,[28] Paraorygmatobothrium exiguum,[29] P. filiforme,[30] and Sphyriocephalus tergetinus,[31] and the copepods Dinemoura discrepans, Echthrogaleus denticulatus,[32] Gangliopus pyriformis,[33] Kroeyerina benzorum,[34] Nemesis aggregatus, N. robusta, N. tiburo,[35] Nesippus orientalis,[36] and Pandarus smithii.[32]