The pathological physiology of Ostertagia circumcincta infestation

Abstract

I. Trials are described in which six sheep and one goat were artificially infested with O. circumcincta and their reactions studied in detail. 2. The main pathological findings were: (i) Marked decrease in packed red cell volume, haemoglobin concentration and circulating red blood cell volume. (ii) A sharp drop in plasma inorganic phosphate which occurred in five of the seven animals. (iii) Anorexia, decreased apparent nitrogen absorption and weight loss or retarded weight gain. (iv) A decrease in plasma albumin, gamma globulin and total circulating plasma proteins. 3. Egg counts were low even with large worm burdens. 4. On reinfestation two sheep cleared themselves of the original and challenging infestation. 5. Large numbers of larvae were necessary to cause death.