Description of Haemonchus placei (Place, 1893) (Nematoda, Trichostrongylidae, Haemonchinae), identification and intra-specific morphologic variability

Haemonchus placei in cattle has never been completely described, possibly d ue to great morphological similarity with small ruminants Haemonchus contor tus. It is newly described on one isolate from Argentina. ii has clear dist inct morphological features from sheep and goats Haemonchus contortus and p resents only two female morphotypes (linguiform and knobbed) instead of thr ee recorded in H. contortus. A key is proposed to identify females. Female as well as male Haemonchus placei from New World (Argentina, Mexico, USA) a re morphologically different from those of Old World (Africa: Burkina-Faso, Mauritania and Ivory Coast) or Australia, possibly due to local evolution since their introduction several centuries ago from Africa or India. We pro pose to differentiate three sub-species, H. placei placei in Australia, H. placei africanus in western Africa and H. placei argentinensis in the New W orld.