A parasitic infection occurs when harmful organisms, known as parasites, invade the body and live off the host. These parasites can be microscopic, like protozoa, or larger, like worms. They often enter the body through contaminated food, water, or insect bites, leading to various health issues. Symptoms of parasitic infections can vary widely, including fatigue, digestive problems, and skin rashes. Common types of parasitic infections include malaria, caused by Plasmodium parasites, and giardiasis, caused by Giardia. Treatment typically involves medications that target the specific type of parasite affecting the host.