Parasite

Any organism living in or on another living creature and deriving advantage from it, while causing the host disadvantage. The parasite obtains food from the host’s blood, tissues, or diet. Parasites may spend only part of their life-cycles with the host or remain there permanently. Some parasites cause few symptoms, while others cause disease or even death. Animal parasites of humans include protozoa, worms, flukes, leeches, lice, ticks, and mites. Viruses and diseasecausing fungi and bacteria are also essentially parasites.