IDENTIFICATION AND CHARACTERIZATION OF ANTICOAGULANT ACTIVITIES IN THE SALIVA OF THE LONE STAR TICK, AMBLYOMMA-AMERICANUM (L.)

Anticoagulant activities against both the extrinsic and intrinsic coag ulation pathways were identified in the saliva of partially fed female lone star ricks, Amblyomma americanum (L.). The activities of factor Xa and thrombin in thr common pathway or the coagulation cascade were inhibited by tick saliva. The greatest anticoagulant activities were f ound in the saliva of ticks weighing more than 200 mg. The anticoagula nt activities in tick saliva could be detected without preincubation o f tick saliva with sheep plasma, but preincubation significantly incre ased the activities. Tick saliva anticoagulant activities were abolish ed by boiling for 15 min or being treated with trypsin for 1 hr. Phosp hatidylcholine (3 mM) and phospholipase A(2) inhibitor oleyloxyethyl p hosphorylcholine (0.2 mM) did not affect the anticoagulant activities significantly, suggesting that the phospholipase A(2) activity found i n tick saliva does not contribute to the anticoagulant activities. Siz e exclusion high performance liquid chromatography revealed that the m olecular weights of the anticoagulant activities were approximately 16 ,000 D. The anticoagulant activities in rick saliva are believed to pl ay an important role in facilitating tick feeding by helping overcome the host hemostatic system.