Pathophysiological changes resulting from intravenous injection of ovine hydatid cyst fluid to sheep.

The pathophysiological changes produced by intravenous administration of ovine hydatid fluid were studied in 40 sodium pentobarbitone-anaesthetized sheep. Hydatid fluid was obtained from the lung and liver cysts of freshly-slaughtered sheep. Fifty per cent of the animals died following intravenous injection of 5-10 ml hydatid fluid. In the latter group, postmortem examination revealed a great amount of mucus in the lower airway, intra-alveolar oedema and haemorrhage, congestion of the pulmonary capillaries and peribronchiolar vessels and of the central sinusoids of the liver. Eighty per cent of the animals (including those which died) developed hypotension and respiratory alterations such as transient apnoea and/or rapid respiration to hydatid fluid administration. The 20% non-reactive animals manifested low blood pressure and respiratory changes when they were reinjected hydatid fluid 48 hours or more after the first test. Pretreatment with the antihistamine chlorpheniramine substantially reduced the fall in blood pressure in 3 out of 8 reactive sheep. Atropine pretreatment failed to block the reactions to hydatid fluid. The responses brought about in sheep by hydatid fluid administration may be due to antigen-antibody reactions or due to pharmacological properties of the cyst fluid.