![]() Inside the snail host, miracidia undergo asexual development and transform into cercariae which emerge from the snails and find out the definitive host. Miracidia penetrate the snail by proteolytic activity and mechanical movement. When eggs contact water, they hatch into ciliated larval forms called miracidia that can sense compatible intermediate snail hosts. Some of the eggs migrate and penetrate the intestines and shed in the stool. Most of the eggs are carried upstream to the liver via the portal veins and its branches and get trapped in the pre-sinusoidal portal venules. The female begins to lay eggs within the mesenteric or pelvic vessels. Then develop to male-female worm pairs, and inhabit either the portal or pelvic vessels. Cercaria penetrate the skin, and transform into schistosomula. Human get infected when they come in contact with fresh water contaminated by cercariae, the infective stage of the parasite. S japonicum uses amphibious freshwater Oncomelania spp snails as its intermediate host (1).The life cycle of schistosoma parasites is completed in two different hosts i.e. Haematobium need certain species of aquatic freshwater Biomphalaria and Bulinus snails, respectively. Haematobium, causing urinary schistosomiasis in Africa and the Arabian peninsula and S japonicum, causes intestinal and hepatosplenic schistosomiasis which localizes to Asia, primarily in China, Philippines, and Indonesia (2). ![]()
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