Worms Flashcards
What are the main different types of Helminths?
There are 3 main classes of Helminths
- Cestodes (tape worms)
- Trematodes (flukes) (incl. schostosoma)
- Nematodes (Roundworms (incl. Hookworm, Strongyloides9
What are the different shapes of the 3 classes of Worms?
- Cestodes (tapeworm) –> Flat, can be long
- Trematodes –> Flukes (small, plane)
- Nematodes (roundworms) –> cylindrical
What are the most important Cestodes?
- Beef and pork tape worms (human worms)
- Echinococcus - dog tape worm
What are the main lifcycles of the pork and beef tapeworm?
Ultimatet host ist Human
Human infected faeces –> ingested by pigs/pork –> cysts in animals –> hedge in humans (usually GI tract). NO cysts in human normal life cycle
NOTE: if humans have cysts –> humans will have eaten human faeces (is the pig in the life-cycle)
What is Echinococcus? Why does it clinically usually cause more problems than pork and beef tapeworms?
Echinococcus is a dog worm (Cestode) with sheep as intermediate hosts
The Lifecycle is the same as Pork and beef tapeworm, but with the dog as ultimate host
Are problematic if humans accidentally become intermediate host –> cyst formation (cysts are the problematic things that kill people)
What is the main management of Tapeworm infection?
- Of worms: Praziquantel (for humans and dogs)
- Of cysts: difficult (as drugs don’t penetrate)
Prevetnsion: hygiene, de-worm dogs, cull foxes
What is the main epidemiology of schistosomiasis?
Differnt sub-types with high prevalence in
Mainly in sub-saharan africa and parts of Brazil and south-east asia (south east asia now almost extinct)
What are the main signs and symptoms of schistosomiasis?
- Acute infection: skin reaction
- incubation period –> with hedging in blod (4-8 weeks) –> fever, cough malaise
- chronic infection (depending on site involved)
Bladder: haematuria, dysuria (+ increased bladder squamous cell carcinoma)
Hepatic. hepatosplenomegaly
Lungs, brains
How is Schistosomiasis diagnosed?
Microscops of urine of stool (visualisation of the eggs)
Serology (antibodies against adult worms)
Biopsy of cysts (can be present)
Explain the life cycle of schistosomiasis
- Humans (definitive host) excrete eggs in urine or faeces
- Eggs hedge in water into miracidia which penetrate into fresh-water snails
- Snails produce sporocyst that replicate asexually into cercadia.
- Cercadia are in water and can penetrate human skin again if in contac with humans
- Worms edge in blood
- Sexual reproduction of worms in bloodstream and migration + lie eggs in target organs (liver, bladder)
What is the main treatment and prevention of schistosomiasis?
Treatment:
Is very easy: praziquantel
Prevention:
Is hard:
Kill snails
Destroy snail habitat
Mass treatment
Interrupt transmission: no swimming, no washing etc
What are the most imporant sub-groups of Nematodes?
What is their main route of transmission?
Nematodes = Roundworms such as
Hookworms
Ascarids
Strongyloides
What are the main helminths transmited through soil?
What is their main mechanism of entry?
Usually differnt types of roundworms (Nematodes)
- Ascaris lumbricoides – ingested with food
- Trichuris trichiura – ingested with food
- Hookworm – transdermal infection
- Plus: Strongyloides stercoralis – transdermal infection
What are the main mechanisms/ causes of disease that infections with roundworms cause?
Very common and hugh burden of disease
Usually in GI system but can have other phases
- Migration (ascaris, hookworm and strongyloides)
- Intestinal obstruction (ascaris)
- Malabsorption and blood loss (all of them)
- Psychological distress
What is Ascaris? What is the routte of transmission?
Ascaris = big big nematode with very big global burden of disease
Transmited through soil (from fecal ingestion of eggs) –> migration through body