AB L2 Helminths Flashcards
What are helminths?
Multicellular, with differentiated organs
Do helminths have a circulatory tract?
No
Size?
<1nm - 10m
Anterior end has…
suckers, hooks or plates for attachment
Where do helminths replicate?
Usually free or in another host, they don’t live their whole lives in humans
Why is is difficult for the immune system to eradicate them? (2)
Have a tough cuticle
Some camouflage by coating with host molecules (e.g. roundworms)
Parasitic helminths feed on…. (2)
Body fluids or intestinal contents
WHO status of helminths:
Many are neglected tropical diseases
Mainly found in what populations?
Rural villages/overcrowed cities
Symptoms include….
malnutrition affecting physical and mental development
Apary from health why else are helminths an issue?
economic cost - e.g. infected cattle
Main classes of helminths
Nematodes (roundworms)
Cestodes (tapeworms)
Trematodes (flukes)
What to nematodes (roundworms) look like?
cylindrical body - no shit.
have alimentary canal - food comes in one side and out the other
What do cestodes look like?
flat, ribbon shape
no digestive tract, nutrients absorbed through the cuticle
What do trematodes look like?
leaf-shaped
blind-branched alimentary tract (in one end, out the same end)
4 e.g. of intestinal nematodes
large roundworm
threadworm
hookworm
whipworm
Most intestinal nematodes are transmitted via …
fecal-oral route
although hookworm larvae penetrate the skin
Symptoms of intestinal nematodes
anal itching, slow growth, anaemia
Another name for roundworm
Ascariasis - may creep out of any orifice
Problems caused by roundworm?
migration of larvae the most common cause of morbidity
blockage of intestines
migration to other organs
Life cycle of roundworm
- learn!
produce 20000 eggs/day excreted in feces mature in soil (3 weeks) ingested hatch and penetrate wall enter lymph/blood carried to liver, heart, lungs - further development coughing brings up adult
blood and tissue nematodes are called….
filariae
where are filarie found? - how transmitted?
blood and lymph, adults discharge larvae that circulate in the blood.
Ingested by insects where the develop into infective larvae.
3 e.g. of blood/tissue nematodes?
river-blindness
elephantitis
loiasis (inflammation of skin and eye)
Cestodes can live for ….
decades
How are cestodes transmitted?
Ingesting a cist in undercooked meat
When do cestodes get dangerous?
Ingestion of egg means larval stages will invade tissue (muscle/brain)
If they stay in the lumen of the gut symptoms are minor
Trematodes live…. and cause damage to…
Live for decades in blood vessels or tissue
progressive organ damage
What do trematodes use as an intermediate host?
Snails
How do you catch yourself a trematode?
eat infected crab/fish
2nd greatest economic impact of a parasitic disease
schistosomiasis (snail fever)
How is schistosomiasis transmitted?
contaminated water (eggs excreted in urine or feces)
Symptoms of schistosomiasis
swimmers itch
2 months later: fever, chills, cough, muscle ache
How does schistosomiasis damage?
eggs stick to tissue and damage is due to immune response - scarring of tissues, lead to bladder cancer
schistosomiasis life-cyle
Free living larvae in water, infect snail
In snail the develop swimming tail
Penetrate human host
Migrate through body - final destination dependent on species (bladder, intestine)
How to diagnose nematodes/cestodes?
Feces sample or just coughing/vomming it up
How to diagnose schistosomiasis?
Eggs in feces or urine sample.
How to diagnose tissue nematode?
Difficult to diagnose adults in tissue
Look at microfilariae in blood
