Nematodes: Larvae Infective for Humans Adult Trichinella spiralis develop, invade intestinal wall of pig,and Capsule Garbage,including produce larvae that invade muscles. undercooked or Section showing T.spiralis raw pork larvae encysted in pig's muscle tissue(capsule is 0.25 to 0.5 mm in length). Section of T.spirolis. ⑤Meanwhile,.other animals are infected by eating infected meat that has been dumped. Undercooked pork Human eats undercooked pork containing cysts. ④In human intestine, cyst walls are removed, and T.spiralis adults develop.Adults produce larvae that encyst in muscles. (a)Life cycle of Trichinella spiralis,the causative agent of trichinosis (b)T.spiralis adult Figure 25.26 Nematodes: Larvae Infective for Humans Figure 25.26