The parasitic hematophagous worm Haemonchus contortus inhibits human platelet aggregation and adhesion: partial purification of a platelet inhibitor.

Blood sucking parasites elaborate mechanisms to counteract the hemostatic system of their victim. Haemonchus contortus worms use several mechanisms directed against the normal platelet hemostatic function. Platelet adhesion onto collagen and fibrinogen, and the ristocetin-mediated interaction of von Willebrand Factor with glycoprotein (GP) Ib were inhibited by the protein extract of adult worms.