Parasites are organisms that feed off a host, using the host's resources to survive. Common examples that affect humans include head lice, ticks, and malaria-carrying mosquitoes. Various types of parasitic worms can also infect the human body, often residing in different organs but typically drawing nutrients from the intestinal wall. If left untreated, these infections can cause significant damage to the affected body parts.
The symptoms caused by parasitic infections can vary widely depending on the type of parasite involved. Parasites that live on the skin, such as head lice, fleas, and mites, may lead to skin problems like itching and rashes. Internal parasites, or endoparasites, such as tapeworms and roundworms, can cause symptoms including diarrhea, stomach pain, weight loss, and nausea. In some cases, fragments of these parasites may be visible in the stool.