The distribution of pepsinogen within the abomasa of cattle and sheep infected with Ostertagia spp. and sheep infected with Haemonchus contortus

The effect of nematode infections on the production of pepsinogen by rumina nts was investigated immunohistochemically and biochemically. Abomasal tiss ues were collected from parasite-naive cattle and sheep, from sheep infecte d with predominantly Ostertagia circumcincta, sheep infected experimentally with Haemonchus contortus and cattle infected with Ostertagia ostertagi. P epsinogen was also assayed biochemically in homogenates of fundic mucosae f rom sheep infected with predominantly O. circumcincta. Infection with Oster tagia spp. parasites was associated mainly with nodular hyperplasia, result ing in increased numbers of cells that produce both pepsinogen and mucus. M easured biochemically, nodules contained more pepsinogen than adjacent more normal mucosa (p < 0.05), and this effect was largely attributable to the greater mass of nodules. Infection of sheep with H. contortus was associate d with generalised hyperplasia, characterised by increased numbers of mucop eptic cells and in at least one animal with reductions in parietal cell num bers. At the same time, the zymogen granule content of chief cells was redu ced. Similar changes were occasionally seen in sheep infected predominantly with O. circumcincta. Generalised hyperplasia is likely to be indicative o f the presence of ambulatory parasitic stages as opposed to those confined to nodules. The potential for the enhanced production of pepsinogen by incr eased numbers of cells with a joint mucous cell and zymogenic cell phenotyp e may offset decreases in the numbers of chief cells or reductions in chief cell activity. (C) 1999 Elsevier Science B.V. All rights reserved.