Trichinella - roundworms from pigs. Enter the capillaries, migrate to the lung and liver. S. mansoni and japonicum migrate to the intestine, S. haematobium migrates to the urinary bladder. The worms do not multiply. The eggs are passed into feces or urine, excreted and infect more snails.
Most infected individuals carry low numbers of worms.
About half of the eggs remain in the host, invade the intestinal wall, liver or bladder and produce hemorrhages. Large granulomas contain the eggs but can block blood flow to the liver or bladder. Worms survive up to 20 years and express decresed levels of antigens, are enclosed into glycolipid coats derived from the host.