Schistosomiasis Flashcards
(59 cards)
What three species of Schistosoma are of vast medical significance?
Schistosoma mansoni
Schistosoma japonicum
Schistosoma haematobium
Where in the body do adult Schistosoma worms typically reside?
Adult worms live within the veins that drain certain organs of their host’s abdomen. Each of the three main species have distinct preferences.
- S. haematobium lives mainly in the veins of the urinary bladder plexus
- S. mansoni prefers the portal veins draining the large intestine
- S. japonicum is concentrated in the veins of the small intestine
Within which veins does S. haematobium typically reside?
Schistosoma haematobium typically resides in the veins of the urinary bladder plexus.
Within which veins does Schistosoma mansoni reside?
S. mansoni resides within the portal veins that drain the large intestine.
What veins do Schistosoma japonicum worms typically reside?
S. japonicum worms are concentrated in the veins of the small intestine.
How many people worldwide suffer from severe Schistosomiasis?
20 million people
What does Schistosoma mean?
Split body- referring to the gynecophoral canal of the male
What types of eggs does Schistosoma mansoni produce?
Laterally spined eggs.
Where is Schistosoma japonicum distributed?
Japan, China, Taiwan, the Philipines and SE Asia.
What term describes the ventral, longitudinal groove on male Schistosoma?
Gynecophoral canal.
Where does the female Schistosoma reside when moving?
The gyncecophoral canal of the male.
What does Schistosoma do to improve motility upstream from smaller veins?
The female Schistosoma positions itself within the gynecophoral canal of the male.
Where does copulation between male and female Schistosoma take place?
Within the gynecophoral canal.
Where are the eggs of Schistosoma deposited?
Within the small venules of the host.
What obstacle must eggs traverse before they can be expelled by the host?
The wall of the venules (small vein) and gut or bladder.
What process aids egg expulsion from the host?
The endothelial lining of the venule moves over the Schistosome eggs to exclude them from the lumen.
What processes may the worm complete to aid transport of the eggs to the gut or bladder lumen?
It may exploit host immune responses.
What process occurs once a Schistosoma egg has been forced out of the venule?
The expelled egg stimulations the formation of a granuloma (mass of cells containing eosinophils, plasma cells and macrophages).
Once the Schistosome granuloma has formed where does it move to?
The granuloma, containing the Schistosome egg moves to the intestinal or bladder lumen.
Once the Schistosome granuloma reaches the bladder or intestinal lumen what occurs?
The granuloma disperses and the egg contained within is expelled in the urine or faeces.
What fraction of Schistosome eggs are retained and not expelled from the host via urine or faeces?
Around 2/3 of eggs are not excreted and accumulate within the bladder or gut wall.
What stimulus triggers the hatching of the Schistsome egg?
Contact with fresh water releases free-swimming miracidia.
Once the miracidia are released in water what process occurs?
Cilia activation continues which allows the miracidium to enter a high spin state.
Once the miracidia reaches its high spin state what occurs?
Osmotically controlled vents open which allows the miracidium to emerge.
