"Parasitic organisms" refers to living things that depend on another organism, or host, for survival. They take nutrients or resources from the host, often causing harm or disease. Full definition
For example, some dogs develop itch because of parasitic organisms on them while others might be just allergic to certain plants. (usbones.com)
Holding wastes parasitic organisms, and wastes may prevent aims for losing belly fat. (deliciouslyella.com)
Their chosen topic of conversation would deprive many people of an appetite, but the scientist and his guest shared an intellectual hunger for a stomach - churning subject: gut worms — specifically, tiny worm - like parasitic organisms called helminths that live nestled in the gastrointestinal tracts of their hosts. (scientificamerican.com)