Studies on resistance in calves to experimental infection with the nodular worm, Oesophagostomum radiatum (Rudolphi, 1803). III. The stimulation of resistance by multiple infections with larval stages

Abstract

Observations are reported on the influence of multiple infections with larval stages of Oesophagostomum radiatum on the stimulation of resistance in calves to reinfection with this parasite. Calves were given spaced doses of infective larvae, and the resulting infections were terminated in the early fourth stage by treatment with an anthelmintic.

The egg counts, numbers of adult worms recovered at necropsy, and the pathological changes observed in the intestine subsequent to a test dose indicated that the reinfected calves had developed a high degree of resistance.

The reinfected calves made significantly lower weight gains than uninfected control calves during the period of exposure to the larval infections.

The results suggest that the immunogenic products of adult worms, and of third stage or early fourth stage larvae, are qualitatively similar.