Helminth Infections Flashcards
What are the other names for threadworms? (2)
Pinworms, Enterobius vermiculaires
Is antihelminitic treatment sufficient to eliminate threadworm infection?
No, medication must be combined with hygienic measures to break the cycle of auto-infection.
Additionally, all members of the family require treatment
What is the life-cycle of threadworms?
- threadworm ova are ingested and exposed to digestive juices in the upper GIT
- worms mature in the large bowel; adult threadworms live up to 6 weeks
- adult females lay eggs on perianal skin, causing pruritus
- scratching the area may lead to ova being swallowed (eg food eaten with unwashed hands)
What non-pharmacological methods may be used to interrupt the threadworm lifecycle? (2)
- Washing hands and scrubbing nails before each meal and after each visit to the toilet
- Taking a bath immediately after rising to remove ova laid during the night
What is the drug of choice for treating threadworm infection?
Mebendazole (single dose with second dose given after 2 weeks to treat reinfection)
- Children and adults: 100 mg for 1 dose (PO) +/- second dose after 2 weeks
What is the causative organism in ascaricides?
Roundworm (ie Ascaris lumbricoides)
What is the treatment of choice for ascaricides?
Mebendazole
100 mg BD for 3 days (PO)
OR
500 mg for 1 dose (PO)
**Levamisole may be used in cases where mebendazole cannot be used, however it is unlicensed for this purpose
Which organisms most commonly cause Taenicides? (5)
(Taenicides = tapeworm infections)
- Tænia solium (intermediate host = pig)
- Tænia sagginatus (intermediate host = cow)
- Diphyllobothrium latum (intermediate host = fish)
- Hymenolepis nana (intermediate host = rat, insect; “dwarf tapeworm”)
- Echinococcus granulosus (intermediate host = sheep)
What is the preferred treatment of taenicides?
Praziquantel (a niclosamide)
Tænia solium:
5-10 mg/kg for 1 dose, to be taken PO after a light breakfast
Hymenolepis nana:
25 mg/kg for 1 dose, to be taken PO after a light breakfast
What is important to remember regarding the Tænia solium life-cycle?
Disease in humans will vary depending on whether the organism is ingested in the ova form or the cyst form:
- “Primary hosting” is caused by eating under-cooked pork that contains CYSTS and results in adult worms in the intestines; generally without symptoms, easily treated
- “Secondary hosting” is caused by ingestion of food or water contaminated by feces from someone infected by adult worms, thus ingesting the tapeworm EGGS instead of the cysts; eggs go on to develop cysts in human muscle (usually asymptomatic) or in the brain (neurocysticercosis = seizures, dementia, HTN, blindness, meningitis, paraplegy, death)
What is the tænia (tapeworm) lifecycle?
- Egg passed into environment through human feces
- Egg ingested by pig or human
- Egg hatches, penetrates intestinal wall, circulates to musculature (or brain), developing into cyst
- Human ingests cyst in pig meat (larval stage), which everts once inside the small intestine
- Larvae migrate to and attach in upper GIT
- Free eggs and detached proglottids are spread through host defecation
- Eggs are ingested by pigs or humans, continuing cycle
(Egg in feces —> hatches into cyst, migrates to muscle (or brain) —> cyst consumed through meat —> adult worm in GIT —> egg in feces —> etc)
What is the treatment of choice for Hydatidiform disease (cysts caused by Echinococcus granulosus tapeworm infection)?
Surgical treatment remains the method of choice in most situations; albendazole is used in conjunction with surgery to reduce the risk of recurrence OR as primary treatment in inoperable cases
What are the two main causes of hookworm infection?
- Ancyclostomiasis
2. Necatoriasis
What is the treatment of choice in hookworm infections?
FIRST LINE:
- Mebendazole
SECOND LINE:
- Albendazole
- Levamisole
What is the treatment of choice in schistosomicides?
Praziquantel
