Trichinella roundworm. Light micrograph (LM) of a Trichinella spiralis roundworm (nematode worm, centre) in a tissue sample. This parasite infects mammals, including humans, pigs, dogs and rats. Infection follows the consumption of raw or undercooked meat which contains the cysts of the T. spiralis larvae. These mature into the adult form in the intestine. The adults live for about 6-8 weeks, during which time the females release large numbers of larvae which penetrate the wall of the intestine. From here they migrate around the body, causing fever and pains and forming cysts in the muscles. Magnification: 100 when printed at 10 centimetres wide