Gastro-duodenal motor and transit disturbances associated with Haemonchus contortus infection in sheep

Abomasal and duodenal motility was investigated by electromyography in 4 lambs fitted with permanent abomasal and duodenal cannulae and infected twice with 25,000 Haemonchus contortus larvae at an interval of 39 days. In addition, abomasal and duodenal pH, flow rate of digesta of the duodenum, and faecal water content were determined. The 80-90 min cycles of antral contractions were shortened for at least 3 weeks after infection. This was accompanied by a 26% increase in the number of duodenal migrating myoelectric complexes/day during the intraparietal development of the larvae (10-12 days). Concomitantly, the duodenal flow of digesta increased from 215 +/- 22 ml/h to 318 +/- 15 ml/h 4 days after infection and was associated with a higher water content of the faeces. The frequency of the migrating myoelectric complexes, but not the duration of antral motor cycles (or the duodenal flow rate), was correlated with both gastric (P less than 0.01) and duodenal (P less than 0.05) pH after the first and second infections. The duodenal flow rate was correlated with the Cl- concentrations of the abomasal contents (P less than 0.01) and with the duodenal pH (P less than 0.05). It is concluded that, (i) the duodenal motor disturbances associated with experimental H. contortus infection are related to the alterations in abomasal gastric acid secretion which occurs during the histotrophic phase of larval development and (ii) the increased duodenal flow is a consequence of ionic permeability changes of the gastro-intestinal mucosae.