Morphological observation experiment of Schistosoma japonicum

Summary

This experiment is from the official website of Parasitology, School of Medicine, Shandong University.

Operation method

Morphological observation experiment of Schistosoma japonicum

Principle

Schistosomiasis is also known as Schistosoma. Parasitic schistosomes in human body are: Schistosoma japonicum, Schistosoma mansoni, Schistosoma aegypti, Schistosoma intermedia, Schistosoma mekongensis and Schistosoma malayanus. China only has Schistosoma japonicum, which is what we usually call schistosomiasis. S. japonicum is distributed in China, Japan, Philippines and Indonesia. In China, S. japonicum is distributed in the middle and lower reaches of the Yangtze River and its southern region in 12 provinces, municipalities and autonomous regions. Schistosoma japonicum parasitizes the portal vein system of humans or other mammals, mainly in the inferior mesenteric vein, and the females lay eggs in the small veins of the intestinal wall, and metamorphosis occurs around the eggs. Eggs fall into the intestinal lumen from the ulcers in the intestinal wall, and hatch out in the water with fecal excretion to invade the nail snail, through the mother cystic larvae, daughter cystic larvae and caecal larvae in various stages, and the caecal larvae escape from the snail body and then invade the human body through the skin. With the portal vein blood flow is transported to the liver eggs, in the interlobular vein along the way to cause metamorphosis, resulting in cirrhosis of the liver. The mode of infection is closely related to the way people live and produce.

Move

I. Self-observation

(a) Schistosoma eggs broken piece specimen: Schistosoma eggs are oval, yellowish, slightly larger than roundworm eggs, thin shell, no cover. There is a small spine on one side of the egg, because the egg is often attached to some dirt, the small spine is often covered and not easy to see. The eggs contain a mature trichinella.

(ii) Slide specimens of caecilians: The caecilians are the infective stage of Schistosoma haematobium, and the whole body is divided into two parts: the body and the tail, and the tail is bifurcated as a characteristic feature.

(c) Adult schistosomes and stained specimens of males and females: males are milky white, on average 10-18 mm long, with both sides of the body curling up to the ventral surface to form a female-embracing groove. The females were more slender than the males, with an average length of 13-20 mm, the anterior end was pointed and thin, the posterior end was thicker and grayish brown. Adults have an oral sucker at the anterior end, followed by an abdominal sucker. The male and female worms are often in a joint embrace. Adult worms are parasitized in the portal vein vessels and are not easily accessible, so they cannot be used for diagnosis.

II. Demonstration

(i) Life history of Schistosoma japonicum: Stages of schistosome development, eggs, trichinellae, female cysticerci, daughter cysticerci, caecal larvae (infective stage), adult worms. Note the site of parasitism of adult worms, the morphology of the intermediate host, the snail, and the morphology of the caecilians.

Oncomelania

(ii) Gross specimen of schistosome eggs deposited in the liver: the eggs caused cirrhosis in rabbits, with a distinct gray fibrous network visible on the surface of the liver.

(iii) Specimens of adult Schistosoma haematobium parasitized in the mesenteric vein (bottled specimens)

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