Species of Marshallagia are abomasal parasites in free-ranging and domesticated ungulates in temperate climatic zones throughout the world. Pervasiveness of these nematodes is significant in various parts of the world. There has been limited research in the area of Marshallagia marshalli pathogenesis. The aim of this study was to investigate the effects of M. marshalli on the serum gastrin concentration and the morphological changes due to parasitic migration to different parts of abomasal tissue in sheep. Ten lambs, approximately around 6 months old, were divided into two groups of five (A and B). Antihelminthic treatment was done to ensure the absence of any worm contamination in lambs. The sheep from group A were infected intraruminally with a dose of 5000 third stage larvae (L3) of M. marshalli whereas the sheep of group B were not infected. 25000 infected larvae (L3) were cultured from sheep infected with 10000 infective L3 of Marshallagia (donor lamb). Jugular blood samples were collected from each lamb twice a week. Lambs were slaughtered after 30 days and abomasal tissues were sampled for histological examination. Serum gastrin concentrations were measured using human ELIZA kit. Sheep and human gastrin have nearly 80% similarity. So in this study human ELIZA kit was used to measure G17. Since, we have no information of serum G17 gastrin values, the measured values were compared. Based on the results of statistical analyzes no significant differences found between the two groups. The results showed that all infected lambs had mucosal lesions of different levels. Both acute and chronic lesions of abomasal tissue section were seen in microscopic observation. Histologic changes include mucosal cell hyperplasia, loss of parietal cells, and inflammatory cell infiltration, with numerous granulocytes and lymphocytes. Hypergastrinemia has been proposed as a diagnostic marker for abomasal parasitism. In this study, there was no significant difference in lamb gastrin level between control and treatment group. There was massive thickening of the antral mucosa at necropsy and histologically severe inflammation which may have damaged the gastrinsecreting G-cell, resulting in the lower serum gastrin concentrations. The exact effect of M. marshalli infection on the serum gastrin concentration is not known and new researches are recommend to be carried out with more larvae in long time.

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