Economic zoology deals with applying zoological knowledge to benefit humanity, such as culturing animals for mass production and controlling or eradicating animals that harm people. Protozoa are microscopic single-celled organisms that can infect humans and cause diseases like malaria, giardia, and toxoplasmosis. Some protozoa classes include sporozoa, flagellates, amoeba, and ciliates. Trypanosoma are parasitic flagellates that cause sleeping sickness and Chagas disease in humans through transmission via insect vectors like tsetse flies and reduviid bugs.