Agglutinins of Trypanosoma, Leishmania and Crithidia in insect haemolymph

The haemolymph of the American cockroach (Periplaneta americana) and the desert locust (Schistocerca gregaria) but not the blowfly (Calliphora erythrocephala) contains agglutinins against the trypanosomatid flagellates Trypanosoma brucei, Leishmania hertigi and Crithidia fasciculata. There was no apparent difference in agglutinin titres between males and females. The preliminary results of selected physico-chemical treatments on the haemolymph suggest that the molecule is a protein or glycoprotein, possesses few or no disulphide bonds, is slightly affected by freezing and thawing, and inactivated by heating at 65°C for 30 min, but whose activity is non-dependent on divalent cations. Infection of locust and cockroach with L. hertigi, but not T. brucei, induced increases in both haemolymph agglutinins and lysozyme levels with maxima being reached on days 4 to 5. Evidence of melanic encapsulation was also observed. These agglutinins and lysozyme may play a role in the defence mechanisms against parasite invasion of the haemocoele and in the natural vector and host play a role in the determination of vector susceptibility.