Vasoconstriction induced by salivary gland extracts from ixodid ticks

• Blood-sucking animals (e.g. sand flies, horse flies, ticks, leeches, vampire bats) produce vasodilators to help them feed.
• Ticks secrete prostaglandins from their salivary glands to induce vasodilation.
• Salivary gland extracts of two ixodid tick species induced vasoconstriction in a pre-constricted rat femoral artery model.
• There was no evidence of prostaglandins in the vasoconstrictive salivary gland preparations.
• Ixodid ticks may use vasoconstriction to restrict blood flow during their prolonged attachment and feeding.

In their quest for blood, most haematophagous parasites secrete vasodilators in their saliva to counter the host haemostatic response of vasoconstriction. Surprisingly, salivary gland extracts from adult female Dermacentor reticulatus and Rhipicephalus appendiculatus ticks induced constriction in a rat femoral artery model; males induced vasoconstriction or vasodilation depending on the time of feeding. Based on comparative HPLC fractionation, the active compounds inducing vasoconstriction do not appear to be prostaglandins (which ticks normally use as vasodilators). Vasoconstriction may be unique to ixodid ticks, helping them control blood flow during their prolonged blood-feeding of up to 10 days or more.

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