life cycle Flashcards
The start of the life cycle?
Eggs are eliminated with faeces or urine
The eggs hatch and form _______, what triggers this?
miracidia
contact with freshwater
How do the miracidia infect the snails?
they swim using cilia located over their surface and infect the snails by penetrating their foot
what is the species species relationship like between snails and schistosoma?
each species of snail is infected by a different schistosoma
What happens to the parasite in the snail?
undergo 2 generations of sporocysts
Where do the sporocysts migrate to in the snail?
hepatopancreas and divide producing cercariae
What emerges from the intermediate host?
cercariae emerge daily depending on ambient temperature and light. They are highly mobile
How is a human infected?
the cercariae penetrate the human skin and shed their tail becoming schistosomulae
what happens to the parasite when it first enters the human?
after becoming schistosomulae it migrates via lungs to the liver using the circulatory system
where do the schistosomulae reside in the liver?
liver sinusoids
after arriving at the liver what happens?
s.mansoni and s.japonicum worms develop an oral sucker and then feed on RBC
worms pair up male and female
what happens to the paired up worms?
migrate to the GI - S.M and S>J
or to the bladder - S.H
when in the GI or bladder eggs are produced, how many?
20-300 = S.m and S.h 500-3500 = s.j
how many eggs are excreted?
about half that are produced
