Internal parasites are organisms that live inside the bodies of their hosts, often causing harm. Common types include worms, protozoa, and flukes. These parasites can infect various animals, including pets like dogs and cats, as well as humans. They typically feed on the host's nutrients, leading to health issues such as weight loss, anemia, and digestive problems. Transmission of internal parasites often occurs through contaminated food, water, or soil. In some cases, they can also spread through direct contact with infected animals. Preventive measures include maintaining good hygiene, regular veterinary check-ups for pets, and proper cooking of food to reduce the risk of infection.