Characterization of haemolytic activity from adult Haemonchus contortus

Adult Haemonchus contortus contain a detergent-soluble factor that haemolyses sheep red blood cells in a time- and concentration-dependent manner. This factor had comparable haemolytic activity at pH 5.0 and 8.0; activity was lower at pH 6.0 and 7.0. The activity was heat-stable, unaffected by proteolytic inhibitors, and inhibited by 20 mM polyethyleneglycol. Haemolytic activity was associated with the particulate fraction of the isolated intestine, suggesting an essential role for this activity in the acquisition of nutrients by disrupting host red blood cells. The data are consistent with the hypothesis that the mechanism of action of the haemolytic factor is as a pore-forming agent.