test 2 schistosomes Flashcards
What does schistosoma mean?
Split body
Describe how the males and females interact.
Males have a ventral groove that the female fits into. they have the same partner for life.
describe the lifecyle of schistosomes (blood fluke).
Pretty much the same as liver flukes except after the cercariae comes out of the snail it goes straight into a person (skips aquatic plant or animal).
What are the differences between blood and tissue flukes.
Similarites: both have oral and ventral suckers, life span is long for both.
Differences:
Blood flukes are slender and wormlike, eggs are non operculated, and sexes are seperate and there is only one intermediate host.
Tissue flukes are flat and leaf like, eggs are operculated, hermaphrodites, and have two intermediate hosts.
Describe the life cycle of the schistosomes.
Eggs hatch in water, releasing miracidia. miracidia penetrate snail tissue where they develop into sporocysts. cercariae are released by the snail back into the water. The cercariae burrow through the skin of a human and get into blood stream. They lose their tails and become schistosomulae. They get into the circulation, migrate to portal blood in liver and mature into adults. mature adults migrate to the mesenteric venules of the bowels/rectum where they lay eggs.
do schistosomes have a rediae stage?
No
How many cercaria can be produced from one miracidium?
up to 4000
How long do the cercaria have to infect a host before they die?
about 8 hours
How do schistosomes hide from the immune system?
they camouflage themselves with host proteins.
what are some of the historical things we talked about in class?
Ancient egyptians believed the advent of manhood was blood in the urine, when this was really just a late manifestation of S. haematobium infection.
S. japonicum infection is believed to have stopped mao’s troops from lauching an assault on taiwan in 1940’s. Mao later mobilized thousands of peasants to destroy the snails.
How do the eggs of schistosomes get out of the body?
eggs are viable for 3 weeks. if they are close to a mucosal surface they may reach the lumen by excreting lytic substance.
S. mansoni and S. japonicum get into the bowel, and S. haematobium gets into the bladder.
how fast can a schistosome penetrate the skin?
in as little as 3 minutes.
Differentiate the places the different types of schistosomes like to live.
S. mansoni: prefers veins draining the large intestines. Humans are principle host but it may infect rodents and monkeys.
S. haematobium: prefers veins draining the bladder plexus. humans are the only host.
S. japonicum: Prefers veins draining the small intestine. zoonotic disease. cattle and water buffalo responsible for 90% of infections in china.
What is the epidemiology for schistosome infectinos.
affects about 200 million people worldwide.
Not transmitted in USA because we dont have the right species of snails here. Land irrigation increasing numbers of people involved.
What is the distribution for the 3 types of schistosomes.
S. mansoni: tropical areas of brazil, middle east, and africa.
S. haematobium: africa and middle east only
S. japonicum: only in asia.
