Parasitic pathogens are organisms that live on or inside a host, deriving nutrients at the host's expense. These pathogens can include various types of parasites, such as protozoa, helminths, and ectoparasites. They can cause diseases in humans, animals, and plants, leading to a range of health issues. These pathogens often have complex life cycles and can be transmitted through different routes, such as contaminated food, water, or direct contact. Common examples include malaria caused by Plasmodium species and tapeworm infections. Understanding these pathogens is crucial for developing effective treatments and prevention strategies.