Effect of meclofenamic acid on the response of parasite-naive lambs and adult sheep to Ostertagia circumcincta

Meclofenamic acid was used to inhibit prostaglandin synthesis in lambs challenged with Ostertagia circumcincta. It lowered the number of parasites which established in treated animals but not significantly. In treated animals plasma pepsinogen values were elevated at the time of parasite emergence but had dropped below the values achieved in control lambs towards the end of the experiment when parasites were at the adult, lumenal dwelling stage. Meclofenamic acid administered to adult immune ewes during challenge with third stage O circumcincta larvae did not significantly affect the establishment of the parasites, nor did it affect the rise in pepsinogen concentration associated with the challenge.