Protozoan parasites are tiny, single-celled organisms that can live in or on other living beings, causing diseases. They are often found in contaminated water or food and can infect humans, animals, and plants. Some common types of protozoan parasites include Giardia, which can cause gastrointestinal issues, and Plasmodium, responsible for malaria. These parasites can reproduce quickly and adapt to their environments, making them challenging to control. Prevention methods include practicing good hygiene, drinking clean water, and cooking food thoroughly. Understanding protozoan parasites is essential for maintaining health and preventing outbreaks of diseases they can cause.