ANTICOAGULANT ACTIVITY IN SALIVARY-GLAND EXTRACTS OF BLACK FLIES (DIPTERA, SIMULIIDAE)

Anticoagulant activity was determined in salivary gland extracts from four species of black flies, i.e., Simulium vittatum Zettersdtedt, Sim ulium argus Williston, Simulium metallicum Bellardi, and Simulium ochr aceum Walker. Inhibition of coagulation factor Xa occurred among all f our, whereas thrombin inhibition was detected in S. argus and S. vitta tum only. Both bovine and human alpha-thrombins were inhibited with th e highest activity occurring with S. argus salivary gland extracts. Fa ctor Xa inhibition was highest in S. ochraceum, an anthropophilic spec ies and vector of Onchocerca volvulus, and lowest in S. vittatum, a pr imiparous autogenous species that is also zoophilic. Total soluble sal ivary gland extract protein also varied among the four species with th e highest concentration measured in S. ochraceum and the lowest in S. vittatum. A positive correlation was observed between the amount of so luble protein and percentage of inhibition of factor Xa for the four s pecies.