Light micrograph of a Trichinella spiralis larva found in the biopsy of a human muscle. This parasitic nematode worm can infect a variety of mammals, including pigs, dogs, rats and humans. Human infection causes the disease trichinosis, which is usually caused by eating contaminated, undercooked pork. The larvae mature in the intestines and produce fresh larvae that migrate around the body, causing fever and pains and forming cysts in the muscles, like this one. The worms are killed by the anthelmintic drug thiabenzadole.