Chapter 9 Flashcards
What is the most important Digenean parasite group
schistosomes
Where do schistosome adults live
intestine or bladder veins
What are male and Female schistosomes like
usually together, females are clasped by male
Are Schistosome F or M larger
didymozoidae- fish, F large, M small
Schistosomatidae- vertebrates, M are large, females small
Describe the life cycle of Schistosomes
- in feces or urine of host,
- eggs hatch in water releasing miracidia
- miracidia penetrate snail tissue,
- sporocysts in snail
- cercariae released into water free swimming,
6 penetrate human host skin
7 cercariae lose tails and become schistosomulae - go into circulation,
- migrate to portal blood in liver and mature into adults
start over
Where do S japonicum schistosomes migrate to as adults in the human body
mesenteric venules of bowel. lay eggs that circulate to liver and shed in stool
Where do S mansoni migrate to as adults in human body
same as japonicum
Where do S haematobium migrate to as adults in the human body
venous plexus of bladder, exit through urine
What are the characteristics of schistosome eggs
have a spine to penetrate gut or bladder, pass in urine or feces and hatch in water
What environmental stimuli do schistosome eggs need to hatch
drop in temp, drop in osmotic pressure, need light, need to be in water
How long do miracidia have to reach a snail host
8-12 hrs
What do miracidia do once inside snail host
asexual reproduction yeids daughter sporocysts or redia
what is special about when cercariae are released
it is rhythmic, occurs during midday, when people are more likely to go swimming,
How long do cercariae have to reach new host
24 hrs, need to burrow through skin
What do schistosomes have specificity for
snail hosts, each fluke has one snail species, not specific for vertebrates
