Schistosoma belongs to trematoda, Polypodiaceae and Schizostera. Adults are parasitic in the veins of mammals (including humans), also known as Schistosoma japonicum or Schistosoma japonicum.
The life history of Schistosoma japonicum includes eggs, metacercariae, female metacercariae, metacercariae, cercariae, larvae and adults.
Adults are parasitic in the portal vein-mesenteric vein system of humans and many mammals, and females lay eggs in the venous endings of intestinal submucosa. Some eggs flow to the portal vein of the liver through the portal vein system and deposit in the liver tissue, while others enter the intestinal cavity through the intestinal wall. Because the secretion of miracidium in mature eggs can penetrate the eggshell, the tissues around the eggs and the blood vessel walls are inflamed and necrotic. When blood pressure, intestinal peristalsis and intra-abdominal pressure increase, eggs can fall into intestinal cavity with broken tissues and be excreted with host feces.
Mature eggs cannot hatch in blood, intestinal contents or urine. Eggs discharged with feces must enter the water, and the feces can only hatch after being diluted below a certain turbidity. After hatching, the miracidium burrows into the Oncomelania hupensis, and then develops into cercaria through the asexual reproduction stage of the mother cyst and the ascocyst. After a cercaria is drilled into the body of Oncomelania hupensis, thousands of cercaria can be produced through asexual reproduction.
After escaping from snails, cercaria can crawl into the skin of the host. After a short stay in the subcutaneous tissue of the host, the worm enters the blood vessels or lymphatic vessels, passes through the right heart to the lungs with the blood flow, and then enters the systemic circulation from the left heart. Children who reach the mesenteric artery can enter the hepatic portal vein through capillaries. After the portal vein of the liver develops to the primary differentiation of sexual organs, the males and females embrace each other, and then migrate to mesenteric vein and rectal vein to live, mate and lay eggs.