Interactions between chemoprophylaxis and immunity to bovine parasitic gastroenteritis and bronchitis: pilot studies using an oxfendazole pulse release bolus.

In separate experiments, the immune status of six matched pairs of yearling heifers from a field trial in which both parasitic gastroenteritis and husk had occurred in control animals, was tested with a single massive challenge of either Dictyocaulus viviparus or Ostertagia ostertagi. The clinical responses of untreated controls and animals that had carried an oxfendazole pulse release intraruminal device (OPRB) were in all cases similar (with the exception of one lung-worm-challenged control that succumbed to a fulminating pulmonary hypersensitivity reaction), indicating that both groups possessed comparable degrees of protection. Faecal larval/egg-output data and serum gastrin levels, however, suggested that larger worm populations had established in the OPRB cattle.