[Physiopathology of ovine ostertagiasis. Effects of experimental infection by Ostertagia circumscripta on various parameters as indicators of abomasum function].

The measurement of the pH and Na+, K+, Ca++ and Cl- concentrations of the stomach or the abomasal contents allow the functioning statement of these organs to be determined. In the present work, these parameters were measured, at 2 day intervals, in six lambs fitted with permanent abomasal cannulae and experimentally infected with 150 000 O. circumcincta infective larvae. Infection was followed by a significant (P less than 0.01) increase in pH and Na+ and Ca++ concentrations, and a significant (P less than 0.01) decrease in K+ and Cl- concentrations of the abomasal contents. The disorders start when the 4th stage larvae begin to emerge from the mucosae (from the 4th to the 12th day infection) and become more marked between the 16th and the 32nd day; this means when the egg output starts and becomes marked. The disturbances noted in the present work suggest: 1) a defective working of HCl production mechanism; 2) an intraluminal diffusion of the interstitial liquid; 3) a stimulation of pepsin production. These disorders would have consequences on the functioning of the other parts of the digestive tract.