INFECTION OF SHEEP WITH ADULT AND LARVAL OSTERTAGIA-CIRCUMCINCTA - ABOMASAL MORPHOLOGY

The infection of parasite-naive sheep with approximately 15000 adult O stertagia circumcincta via abomasal cannulae resulted in marked change s in the structure and function of the abomasum. The functional change s, which have been characterised previously, included elevated abomasa l pH and increased serum concentrations of pepsinogen and gastrin. Eig ht days after the transplant of adult worms, the abomasa of recipient animals were significantly heavier than those of controls (P < 0.001), the thickness of the fundic mucosa was greater (P < 0.01), there were fewer parietal cells (P < 0.01) and increases in the numbers of mitot ic figures and mucus-producing cells. Mucous cell hyperplasia was also evident in the fundic mucosae of sheep receiving a trickle infection of infective, third-stage O. circumcincta larvae and was prominent wit hin nodules associated with larval development. in non-nodular mucosa, there was hyperplasia of mucous cells and changes in the distribution of parietal cells. Decreases in the number of parietal cells at the g land base were offset by increases at a mid-gland level, probably due to chronic hypergastrinaemia, so that, overall, total parietal cell nu mber was unaffected. Mucous cell hyperplasia and the diminution of par ietal cell number are seen in a diverse range of disease states and ma y be mediated by host growth factors such as Transforming growth facto r-alpha. Alternatively, the cellular and/or the secretory changes in r esponse to the presence of adult worms are mediated by chemicals that are cytotoxic/inhibitory for parietal cells, and released by the paras ites themselves. (C) 1998 Australian Society for Parasitology. Publish ed by Elsevier Science Ltd. All rights reserved.