Plasma pepsinogen levels in some experimental infections of Ostertagia ostertagi in cattle.

Two groups of calves were infected with larvae of Ostertagia ostertagi to establish large numbers of adults and arrested larvae. In one group symptoms of ostertagiasis were seen and there was a loss of three months growth; in the other, in which adult worms were removed by a single anthelmintic treatment, there was only a transient reduction in live-weight gain. Plasma pepsinogen levels were however the same in the two groups and followed the same course. Even after 25 weeks, when calves had been growing normally for up to three months, plasma pepsinogen values were still around 5 iu per litre, well above the level generally regarded as diagnostic of ostertagiasis. The relevance of these findings to the use of the test in the diagnosis of ostertagiasis is discussed. The literature is reviewed.