Life cycle Schistosoma spp. Flashcards
What is the classification of Schistosoma spp?
Helminth in the category of trematodes flukes (flatworm)
What specicies of Schistosoma are infective for humans?
S. Mansoni
S. Japanicum
S. Makongi
S. Haematobium
How is Schistosoma spp. transmitted?
In water through larvae
Excreted eggs leave the body through urine (S. Haematobium) and stool (S. mansoni, S. Japanicum, S. Mekongi)
What are the steps of the Schistosoma lifecycle outside of the human host?
- Eggs shed from infected humans in urine and feces and get into the water. S. Mansoni, S. Japonicum, S. mekagi through feces. S. haematobium through urine
- Eggs hatch and release miracidia
- Miracidia penetrate snail tissue
- Sporocysts develop in snail (successive generation)
- Free swimming cercariae are released from the snail into the water, they have a tail
What are the lifecycle steps of Schistosoma lifecycle in the human host?
- Cercariae penetrate the human skin
- Cercariae lose tails during penetration and become schistosomulae
- Schistosomulae go into the blood circulation (other organs?)
- Migration to portal blood in lever and maturation in adult worms.
- Paired adult worms from the S. Mansoni, S. Japonicum, S. Mekongi species migrate to the mesenteric venules of the bowel/rectum laying eggs that circulate to the liver and shed in stool Paired adult worms from the S. haemotobium species migrate to venous plexus of bladder; eggs shed into urine.
Which type of life cycle does Schistosoma spp have?
Indirect life cycle
What is the definitive host and intermediate host for Schistosoma spp?
Aquatic snail: Intermediate host
Human: definitive host
What is the reservoir for Schistosoma spp?
Animals like cattle, dogs, cats etc.
What causes the symptoms of a Schistosoma infection?
Caused by the systemic reaction against the micrigenst systosomise.
What are the symptoms of Schistosoma spp. infection?
Many are asymptomatic but it can cause hypersensitivity of skin (light rash named swimmers rash). Other symptoms are fever, cough, abdominal pain, diarrhea
Occasionally it can lead to central nervous system lesions. Cerebral granulomatous disease may be caused by ectopic S. Japonicum eggs in the brain and granulomatous lesions around ectopic eggs in the spinal cord may occur in S. mansoni and S. haematobium infections.
What is the incubation time for Schistosoma spp. infection?
2-12 weeks after infection
Where is Schistosoma spp. endemic?
Worldwide but the problem is biggest in Africa.
S. Haematobium is found in Africa and pockets of the middle east
S. Japonicum is found in China, the Philippines, and Sulawesi
S. mekongi is in Cambodia and Laos
S. Intercalatum is only in the democratic republic of the Congo
S. guineensis is found in west Africa
Depends on the aquatic snail
How is Schistosoma spp. diagnosed?
Microscopy of urine & feces
