On the immunological response of young calves to light Nematodirus helvetianus infection.

Infecting parasite-free eight week old calves with 8,000 infective Nematodirus helvetianus larvae did not modify appreciably their response to a later heavy field challenge with N. helvetianus, Ostertagia ostertagi and Cooperia oncophora, although two of six animals did have smaller Nematodirus burdens.