Eukaryotic Parasites 2 Flashcards
What are the 3 major types of helminths?
roundworms, tapeworms and flukes
Why is the life cycle of helminths different to other parasites?
Because they develop their eggs outside of humans - in another animal, or in soil or in a plant
What is the exception to this?
strongyloides - can complete sexual reproduction in human host
What are nematodes?
roundworms
What are enterobius vermicularis?
pinworms - highly contagious roundworms that live in the lower colon and rectum
What is the life cycle of pinworms?
Female pinworms crawl out of the anus at night and lay eggs - the eggs are ingested by humans and the larvae hatch in the small intestine and become adults and mate in the caecum
What is pinworm infection uncommon in adults?
better hygiene
How long will pinworms live for if they can’t reinfect?
4-6 weeks
What is the treatment for pinworms?
antihelminthic
What is ascaris lumbricoides?
a large intestinal roundworm
What does ascaris lumbricoides cause?
GI obstruction, respiratory obstruction, cholecystitis, pancreatitis, pneumonitis - but mainly asymptomatic
What is the lifecycle of ascaris?
Eggs are laid in the jejunum and then go into the faeces which will contaminate soil, eggs will mature in subtropical or tropical soil and then will reinfect humans via a contaminated water supply or plants - the larva hatch in the small intestine and then migrate through hepatic circulation to the lungs - in the lungs they go into alveolar spaces and then go back up the trachea to be swallowed
What is the treatment for ascaris?
antihelminthics
What is strongyloides?
a roundworm that can cause infection by skin penetration
Why is strongyloides a risk factor for gram negative sepsis in immunosupressed patients?
because immunosupression will cause dissemination and bring with it gram negative organisms
Why is strongyloides different from other helminths?
Because auto infection can happen - can happen decades after leaving an endemic area
What is the life cycle of strongyloides?
larvae in the intestine are excreted into the stool, develop into free living worm adults, produce eggs, eggs hatch infective larvae and penetrate the skin. Or the larvae can remain in the intestine and penetrate intestinal mucosa - self infection.
How are stongyloides treated?
antihelminthic
What is schistosoma mansoni?
A fluke that causes bilharzia
Where does schistisoma live?
mucosal associated veins - GIT or urinary
How does schistisoma infect?
it is transmitted by fresh water snails and penetrates the skin when swimming
What is the distribution of schistisoma?
africa, tropical south america, carribean - need an area with fresh water snail and human contact
What are the symptoms of a schistisoma infection?
in an acute infection only an itch and non specific febrile, if a chronic infection - hepatomegaly, splenomegaly, collateral circulation, portal hypertension, pulmonary fibrosis
What is the treatment of schistisoma?
antihelminthic
What is one way of controlling schistisoma infections?
snail control with molluscacides
What is the life cycle of schistisoma?
penetrates skin, travels through blood to the liver, enters portal venous system, matures in portal veins, migrates to venules of large bowel, lays eggs in blood stream and gut lumen, eggs passed out through faeces, returns to water supplies, hatch in water, penetrate fresh water snails
What is the general effect of all tapeworms?
They consume nutrients - causes most of their impact
What is echinococcus granulosus?
tapeworms where humans are accidental intermediate hosts
What does echinococcus cause?
hyatid cysts in the liver and lungs
How is echinoccous transmitted?
With sheep or goat contact in rural areas
What is the definitive host of echinococcus?
dogs
What happens if a cyst from echinococcus bursts?
It causes a very immunogenic anaphylactoid reaction
How is echinococcus treated?
pre treat with an antihelminthic agent or ‘puncture aspiration injection resaspiration’ to reduce the size of the cyst before removal with surgery
What is taeniasis?
cestode parasites causing neurocysticercosis (cysts in the brain)
What kind of hosts are humans for taeniasis?
either definitive or intermediate (not necessary hosts)
What are the symptoms of taeniasis infection?
may be asymptomatic or may cause epileptic foci
How do you commonly get a taeniasis infection?
eating undercooked meat - meats that aren’t under controls are more of a risk
How is taeniasis treated?
with antihelminthics - but won’t treat unless necessary as treatment may cause an immune response
What is the distribution of taenia solium?
africa, latin america, asia
