Phlebotomine sand flies are telophagic feeders, and consequently skin penetration by the mouthparts is shallow. Saliva is introduced into the site while feeding and contains the antihemostatic apyrase, vasodilators and immunosupressants. Of particular interest are two unidentified salivary proteins; one is known as EIF, Erythema Inducing Factor, which increases blood flow to the bite area and the other is LEF, Leishmania Enhancing Factor, (Ribeiro, 1987). LEF seems to have antimacrophage activity and be used by the parasite to drastically improve its ability to infect its host. As few as a dozen Leishmania spp. protozoan promastigotes injected directly into a host in the presence of fly saliva can initiate an infection while ten times as many injected without, are quickly immobilized and destroyed by the host immune system (Titus and Ribeiro, 1988).

Sand flies also possess a powerful vasodilator (another EIF) named maxadilan. Initial studies indicate that maxadilan is similar to the vasodilator/macrophage inhibitor calcitonin gene-related peptide (CGRP) but about 500 times more powerful as a vasodilator and 10 times as more potent as an antimacrophage. Maxadilan may be responsible for the antimacrophage activity noticed in the presence of saliva, but this is still under investigation (Beaty and Marquardt, 1996).