MI: Worms Flashcards
What are 3 main types of helminths and some examples?
Cestodes (tapeworm)
- Hydatid
- Pork / beef / fish tape worm
Trematodes (Flukes)
- Lung, liver, intestinal
- Blood (schistosoma)
Nematodes (Roundworms)
- Hookworms
- Ascarids
- Stongyloides
Describe the tapeworm lifecycle
What are hyatids?
Dog tape worm (echinococcus)
- Dog and foxes are definitive hosts
- Encyst in liver, lungs
- Complications due to cyst rupture or mass effect
Describe the lifecycle of hyatids?
How are cestode infections diagnosed?
Visualisation, serology and imaging
How are cestode infections treated (tapeworm and hyatid)?
PAIR - puncture, aspiration, injection, reaspiration
Describe the lifecycle of schistosomiasis
Lifecycle
- Cercariae invade human skin when in contact with contaminated water.
- Worms develop in venous plexus
- Eggs excreted in faeces or urine
- Hatch into miracidia, which parasitise snails
- Snails release cercariae
Adult schistosomes lay eggs
- Migration of eggs through bladder or bowel causes damage
- Retrograde passage of eggs into the liver causes “cirrhosis”
Where is schistosomasis endemic to?
Africa, SE asia, South America
How is schistosomiasis diagnosed?
Microscopy - seeing the eggs
- Urine - S. haematobium
- Stool - S. mansoni, S. japonicum
Serology
Biopsy
Response to treatment
Treatment of schistosomiasis
Praziquantel
Prevention (hard) - kill snails, education (no swimming or washing)
What are 4 soil-transmitted helminths?
- Ascaris lumbricoides
- Trichuris trichiura
- Hookworm
- Strongyloides stercoralis
Ascaris lifecycle
Ingested with food
How many people affected in Ascaris in world
1 billion
Describe the lifecycle of strongyloides
Only helminth capable of autoinfection
- Larvae invade skin
- Mature into adult pinworms in the small bowel
- Eggs produced, hatch into rhabtidiform larvae
- These mature into filariform larvae (infectious)
- These can autoinfect via perianal skin
How do strongyloides cause damage?
Generally asymptomatic
- Hyperinfection
- Larva currens
- Malabsorption
How is strongyloides treated?
Ivermectin
What is filariasis?
Nematode infections spread by blackflies and mosquitoes
Categories according to the worm tropism
- Lymphatic filariasis (Wuchereria, Brugia)
- Subcutaneous filariasis (Onchocerciasis, Mansonella, Loa loa)
- Serous cavity filariasis (Mansonella, Dirofilaria)
Adult worms release larvae (microfilariae) taken up by vector
How does tissue damage occur in filariasis?
- Adult worms: lymphatic filariasis (elephantiasis, scrotal swelling), also oncho (nodules)
- Microfilariae: Onchocerciasis (depigmentation, river blindness)
How is filariasis diagnosed?
- Microscopy - blood film, skin snips
- Serology (ELISA)
- Imaging - find adult worms (USS dance sign)
How is filariasis treated?
Combination of ivermectin and diethylcarbamazine (DEC) with albendazole
Describe the lifecycle of filariasis
What is myiasis?
Asphyxiate larve by covering wound with vaseline
What is this?
Ginea worm - only worm that comes out your leg
Worms coming out of febrile child?
Nematode (ascaria) - does not like heat
What is this?
Dog hookworm
- Someone stepped in sand infected with dog poo
- Dog hookworms cannot migrate properly so remain local to invasion site
Describe 2 main parasite screening investigations.
- Microscopy
- Serology
What is commonly seen on FBC in helminth infection?
Eosinophilia
