Veneza zonata (Hemiptera: Coreidae)/trypanosomatid relationship: action of hemolymph in vitro and experimental infection.
The defense response of Veneza zonata (Hemiptera: Coreidae) against three different trypanosomatid infections was assessed: (1) strain 714TD, a Leptomonas which has V. zonata as vector of a plant trypanosomatid, (2) strain 563TD, a Leptomonas isolated from the digestive tract of Euchistus heros (Hemiptera: Pentatomidae), and (3) Leishmania (L.) amazonensis, a human parasite that cannot infect V. zonata. Experiments with V. zonata hemolymph showed agglutination only of L. (L.) amazonensis culture forms and hemocytic recognition was more intense with this strain. L. (L.) amazonensis also activated the prophenoloxidase system, whereas strains 714TD and 563TD did not activate this system but rather seemed to inhibit phenoloxidase activity. No flagellates were seen in the digestive tract, hemolymph, or salivary glands in insects infected with L. (L.) amazonensis. The digestive tract, the hemolymph, and the salivary glands of insects fed on tomatoes inoculated with 714TD are sequentially invaded by the flagellate, which is inoculated in plants together with saliva. Insects fed on tomatoes inoculated with 563TD exhibited culture forms in the digestive tract (6 days after) and hemocoel (three additional days); however, they died 12 to 14 days after exposure. The salivary glands in insects inoculated in the hemocoel with 714TD strain are rapidly invaded, whereas those with 563TD culture forms died approximately 24 h after infection. Bacterial proliferation in the hemocoel and hemocyte surface blebbing were seen in insects infected only with 563TD strain as the probable pathogenic mechanism of insect death.