Pathophysiological and parasitological studies on Cooperia oncophora infections in calves.

Calves which had received daily infections of Cooperia oncophora over a six week period showed inappetence, weight loss, impaired nitrogen retention and a loss of plasma proteins into the gut. During this period the infections occurred in the duodenum, jejunum and ileum and many larval stages were present in the mucosa of the small intestine. At necropsy, on weeks 3, 6 and 10 after the first infection, stunting and thickening of the villi were noted with excessive mucus production. Prior administration of a morantel slow release bolus prevented these changes. By week 12 most of the worms had been expelled yet a loss of plasma proteins to the gut was still occurring.