Endocrine Responses of Sheep to Infection with Trichostrongylus colubriformis

The plasma concentrations of corticosteroids, insulin and thyroxine in sheep infected with Trichostrongylus colubriformis were determined and compared with those in non-infected pair-fed controls. Corticosteroid levels rose for both infected and pair-fed sheep, but the increase was much greater in infected animals. Insulin was depressed in both infected and pair-fed animals to a similar degree when feed intake fell. Thyroxine levels fell in infected sheep, whereas pair-fed animals showed no change.