GLOBAL AGROVET RESEARCH CONFERENCE

22 December 2025

Targeting Intracellular Calcium Release: A Strategy of Hyalomma anatolicum Ticks to Suppress Platelet Aggregation

22 December 2025

Ticks are obligate blood-feeding arthropods that secrete a range of bioactive compounds into the host’s bloodstream during feeding. Few of these molecules interfere with the host’s hemostatic mechanisms, thereby facilitating uninterrupted blood flow to support the tick’s nourishment. Infestation of ticks causes irritation, damage to hides, depression of immune function and transmission of wide variety of pathogenic micro-organisms like Theileria annulata, Babesia bigemina etc. in animals. These tick-borne pathogens are responsible for causing theileriosis, babesiosis, anaplasmosis etc. in animals whereas spotted fever rickettsioses, recurrent fever borrelioses, Q fever, tularemia and Crimean-Congo hemorrhagic fever in human beings. So, the aim of the present study was to isolate the platelet aggregation inhibitors from the salivary glands of Hyalomma anatolicum ticks. For this, salivary glands of adult female ticks were dissected and homogenized on ice in HEPES saline buffer (pH 7.0), centrifuged and the supernatant was fractionated using gel filtration chromatography. The total protein concentration was quantified. For platelet aggregation assays, bovine platelets were isolated and exposed to different treatments: salivary gland fractions, an agonist (thrombin), and an antagonist (Gly-Pro-Arg-Pro amide). Fractions exhibiting anti-platelet aggregation activity were then evaluated for their effect on intracellular calcium release by monitoring changes in fluorescence intensity by the Fura-2 labelled platelets. Fura-2 is a ratiometric fluorescent calcium indicator dye which was used to measure intracellular calcium concentration in platelets. Unlike agonist, all the fractions of H. anatolicum significantly (p < 0.05) inhibited intracellular calcium release, with inhibition levels comparable to those observed with the antagonist. The mean ± SE values of fluorescence emitted were 39265.2 ± 797.5 for the agonist, 26541.7 ± 1395.8 for the antagonist, and ranged from 23792.2 ± 1240.6 to 26314.5 ± 639.5 for the fractions. These findings suggest that the inhibition of platelet aggregation is likely mediated through the suppression of intracellular calcium-release, which is critical for platelet aggregation.

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