Effects of ovine hydatid cyst fluid in sheep before and after treatment with hydrocortisone, antihistamines and atropine.

The cardiovascular and respiratory responses to scolex-free ovine hydatid cyst fluid were studied in 65 sodium pentobarbital-anesthetized sheep. The arterial blood pressure (ABP), central venous pressure (CVP), stethogram and electrocardiogram were recorded. Intra-venous administration of 10 ml or less hydatid fluid brought about moderate to severe fall in ABP and rapid respiration or permanent respiratory cessation in majority of the animals. Forty six percent of the sheep died of circulatory and respiratory failure after the first injection or the hydatid fluid. Boiled hydatid fluid did not lose its potency to evoke the above responses. Hydrocortisone, given 200 mg daily for seven days, failed to prevent the reactions to hydatid fluid. Intravenous administration of the antihistamines chlorpheniramine, 4 mg/kg, and antazoline, 5 mg/kg, caused only partial prevention of the responses in 8 out of 15 responsive sheep. Pretreatment of the animals with atropine, 0.5--1 mg/kg subcutaneously, did not block the reactions. The cardiovascular and respiratory responses to ovine hydatid fluid may be due to antigen-antibody reactions or some toxic component of the fluid.