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TROP939 > helminths > Flashcards

helminths Flashcards

1
Q

What is a key difference in the lifecycle of nematodes and platyhelminthes?

A

Nematodes get bigger through their lifecycle but cestodes and trematodes look different at all stages in life cycle.

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2
Q

What does dioecious mean? Which helminths are?

A

Separate sexes

all nematodes and schistosoma species

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3
Q

What are DALYs?

A

Disability Adjusted Life Years
It is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death.

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4
Q

Which STH has the biggest health burden?

A

Ascaris lumbricoides

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5
Q

What is MDA?

A

Mass drug administration (MDA) is the administration of a treatment to every member of a defined population or every person living in a defined geographical area (except those for whom the medicine in contraindicated) at approximately the same time and often at repeated intervals.

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6
Q

Life cycle of Ascaris lumbricoides

A
  1. Adults reside in small intestine, eggs in faeces
  2. eggs mature in external environment
  3. embryonated eggs ingested from soil/ contaminated food
  4. L3 larvum hatch and penetrate gut wall, migrate to lungs via bloodstream
  5. migrate up trachea and swallowed back into the gut where they mature
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7
Q

treatment of nematodes

A

albendazole/mebendazole

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8
Q

Life cycle of Trichuris trichuria

A
  1. Unembryonated eggs passed in faeces
  2. Eggs mature in external environment
  3. Embryonated eggs are ingested
  4. Larvae hatch in small intestine
  5. Adult worms embed into well of caecum and large bowel
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9
Q

Diagnosis of trichuris

A

stool microscopy or colonoscopy

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10
Q

Life cycle of Hookworm species

A
  1. Eggs in faeces
  2. develop in external environment into filariform larvae
  3. penetrate skin ‘ground itch’
  4. bloodstream transport into lungs
  5. migrate up trachea and swallowed by gut
  6. adult worms develop in SI
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11
Q

Life cycle of Enterobius vermicularis ‘pinworm’

A
  1. Eggs on perianal skin
  2. Maturation on skin surface
  3. Scratching - picks up eggs on hands/ bed linen
  4. Ingestion of embryonated eggs by same host ‘auto-infection’ or another host
  5. larvae hatch in SI
  6. Adult worm in caecum
  7. Adult females migrate out through anus to lay eggs on skin
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12
Q

Diagnosis of Enterobius

A

Scotch tape method, peri-anal swab, lookunder microscope

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13
Q

What are the different life cycles of Strongyloides stercoralis

A

Free living worm in environment, direct parasitic life cycle in host, autoinfection cycle

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14
Q

Diagnosis of strongyloides

A

larvae in faeces or sputum, concentrate stool, charocoal cultures, antibody detection, pcr

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15
Q

Which infection is more intense- Ascaris or Trichuria?

A

Ascaris - higher egg count in faeces (200,000 per day) compared to Trichuria (20,000)
In Ascaris larvae enter bloodstream and migrate to lungs
in trichuris larvae hatch in SI and embed into caecum.

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16
Q

Name the cestode species

A 
Taenia saginata–‘beef tapeworm’
Taenia solium–‘porktapeworm’
Diphyllobothrium latum–‘fish tapeworm’
Hymenolepis nana –‘dwarf tapeworm’
Echinococcus spp.
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17
Q

What is the general morphology of cestodes?

A

tapeworm with scolex (head) with hooks or suckers for attachment and proglottids (segments). they’re hermaphrodite

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18
Q

Generalised cestode life cycle

A
  1. Adults in small intestine
  2. Proglottids break off which hold eggs
  3. Eggs shed in faeces
  4. Ingestion by intermediate host
  5. Develop into metacestode (juvenile)
  6. Definitive host ingests metacestode
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19
Q

Which cestode does not require an IM host?

A

Hymenolepsis nana

20
Q

What drug is used to treat cestodes?

A

Praziquantel

21
Q

How do you acquire D.latum?

A

Ingestion of raw or undercooked fish

22
Q

What IM hosts are there of D.latum?

A
  1. cyclops ‘water flea’

2. fish

23
Q

Brief life cycle of D.latum

A
  1. Eggs released in faeces
  2. Hatch into ciliated larvae in freshwater
  3. Cyclops ingest
  4. Fish ingest cyclops
  5. Definitive host eats fish
  6. Adult worm in small intestine
24
Q

What parasite causes cystercicosis?

A

Taenia solium

25
Q

What are the main differences between T.solium and T.saginata?

A

T.saginata: eggs do not infect humans, only cysticercus infective to humans, only adult worm present
T.solium: Eggs do infect humans, cysticercus AND egg is infective to humans. Adult worm AND juvenile cysts present

26
Q

How can you prevent infection with Taenia?

A

Mass chemotherapy with praziquantel, improve sanitation, reduce carriage in intermediate hosts (animals: vaccinate, treat, remove from sewage areas), meat inspections, cook meat well

27
Q

Name the liver flukes

A

Fasciola hepatica, Opisthorchis viverrini

28
Q

Describe life cycle of the liver flukes

A
  1. Eggs released into environment
  2. Miracidia hatch from eggs and penetrate intermediate host (water snails)
  3. Amplification by asexual reproduction in snail
  4. Cercariae released
  5. Metacerciae encyst on plants (Fasciola) fish (Opisthorcis)
  6. Ingestion by humans/cattle/sheep
  7. Excystment in duodenum
  8. Penetrate gut wall and migrate to liver where they become an adult fluke
29
Q

treatment of Fasciola hepatica

A

triclabendazole

30
Q

What’s the difference between Fasciola hepatica and Fasciolopsis buski?

A

Fasciola adult flukes reside in billiary ducts in the liver, Fasciolopsis adults reside in intestinal mucosa in gut.

31
Q

What is the name of the lung fluke?

A

Paragonimus westermani

32
Q

Describe the life cycle of Paragonimus westermani

A
  1. Eggs in faeces (when swallowed) or sputum
  2. Miracidia hatch and penetrate water snail
  3. cercariae released
  4. Metacercarie encyst on crustacean (crab)
  5. Ingestion of crabmeat by definitive host (human/cat/dog)
  6. Adult fluke resides by airways
33
Q

Describe general life cycle of Schistosomes

A
  1. Eggs passed in faeces (mansoni) or urine (haematobium)
  2. Miracidia hatch and penetrate snail
  3. cercariae released
  4. penetrate skin of waders/bathers ‘swimmers itch’
  5. cercariae lose tail ‘schistosomulae’ and migrate through circulation
  6. paired adult worms in venous plexus (blood) of gut (mansoni) or bladder (haematobium)
34
Q

What is the difference in life cycle of S. mansoni and S. haematobium

A

In haematobium parasite resides in blood vessels of urinogenital system, invades bladder and enters urine-linked with bladder cancer.
In mansoni, parasite resides in blood vessels of gut and passes out in faeces.

35
Q

Why is the development of an RDT important for schistosomiasis?

A
  • to identify species
  • where the tissue eggs are
  • how many worms-infection increases with number of eggs
36
Q

What are the symptoms of schistosomiasis?

A

abdominal pain, diarrhoea, blood in stool, liver or spleen enlargement, blood in urine (haematobium)

37
Q

Treatment for all flukes

A

schisto: praziquantel and albendazole
paragonimus: praziquantel
fasciola: triclabendazole
opisthorchis: praziquantel and albendazole

38
Q

Methods of control for schistosomes

A

MDA of praziquantel to interrupt transmission, snail control, improve sanitation, health education

39
Q

life cycle of trichinella spiralis

A
  1. larvae infested in undercooked meat
  2. larvae released in stomach
  3. adults in SI
  4. females release larvae that enter lymph/ blood (cause cell death of heart cns kidney lover lungs)
  5. larvae encyst skeletal muscle
  6. larvum matures in skeletal muscle /nurse cell
40
Q

describe life cycle echinococcus

A
  1. eggs released in animal faeces
  2. ingest by sheep
  3. cystic lesions in solid organs (liver and lungs)
  4. ingestion by canines of cysts of sheep

humans are accidental hosts

41
Q

where do hydatid cause problems

A

liver
brain
lungs

42
Q

main method of control for helminths

A

mda of benzimidazole drugs once or twice a year, donated by pharma

43
Q

control of opisthorchis

A 
encourage proper cooking of fish
targeted or mass chemotherapy-repeated doses as part of an integrated campaign
health education
improved disposal of human faeces
limit use of faeces as fertiliser
snail control
44
Q

intermediate hosts of schistosomes

A

Bulinus- haematobium

biomphalaria-masoni

45
Q

apart from faecal smear what other lab based diagnostic methods could be used to detect taenia

A

detection of proglottids
coproantigen tests
swab around anal akin
concentration method for stool

46
Q

other techniques more sensitive than direct wet mount of faeces

A

formal ether concentration technique

kato kaz

47
Q

describe kato kaz technique

A

faeces passed through mesh to remove large particles
portion of sieved sample transferred to hole of a template on a slide
template removed and sample covered with cellophane covered in glycerol- glycerol clears faecal material around the eggs

TROP939 (14 decks)

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