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Parasites > Helminths > Flashcards

Helminths Flashcards

1
Q

What are the worms?

A
  • Nematodes (roundworms - filaria)
  • Trematodes (flukes or flatworms)
  • Cestodes (tapeworms)
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2
Q

What are the diagnostic methods?

A
  • See adult worm, larvae or eggs (worms may produce huge numbers of eggs daily, examination of faeces/blood/skin)
  • Antigen detection
  • Serology
  • PCR
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3
Q

What are invasive helminth infections often associated with?

A

Eosinophilia

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4
Q

What are the 4 different types of hosts?

A
  1. Definitive host (parasite reaches maturity or reproduces sexually)
  2. Intermediate hosts (harbour parasites during development stage)
  3. Paratenic hosts (intermediate host but parasite doesn’t develop further)
  4. Accidental/dead hosts (gets infected but don’t contribute to parasite’s ongoing life cycle as not a suitable predator)
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5
Q

What does Nematodes infect?

A
  • Intestinal
  • Blood and tissue
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6
Q

Describe intestinal nematodes

what worms? where? where egg hatch? how many stages?

A

Adult worms in human/animal intestine
- Two sexes
- Eggs hatch in environment or in host
- Several larval stages

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7
Q

How to diagnose intestinal nematodes?

A
  • Characteristic eggs, larvae (concentration techniques on stool)
  • Serology (some)
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8
Q

What are the intestinal nematodes species?

A

- Enterobius vermicularis
- Trichuris trichiura
- Ascaris lumbricoides
- Stronglyoides sterocoralis
- Trichinella spiralis
- Toxocara canis, T.cati
- Hook worms

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9
Q

Pathogenesis of Enterobius vermicularis

issa pinworm, threadworm

A
  • Humans swallow eggs
  • Hatch and worms mature
  • Female lay eggs on perianal/perineal skin

Reinfection of original host is common

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10
Q

What does Enterobius vermicularis cause?

issa pinworm, threadworm

A

Pruritus ani

don’t scratch bum or suck your thumb!

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11
Q

How to diagnose Enterobius vermicularis?

issa pinworm, threadworm

A

Sellotape slide, characteristic eggs

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12
Q

Pathogenesis of Trichuris trichiura

issa whipworm

A
  • Eggs passed in faeces
  • Humans swallow eggs
  • Larvae develop into adult in GIT
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13
Q

What are the clinical presentation of Trichuris trichiura?

issa whipworm

A
  • Bloody stools
  • Rectal prolapse
  • Abdominal pain
  • Trichuris Dysentery Syndrome (chronic diarrhoea, growth/intellectual retardation)
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14
Q

How to diagnose Trichuris trichiura?

issa whipworm

A
  • Eggs in faeces
  • Worms in rectal mucosa
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15
Q

Pathogenesis of Ascaris lumbricoides

issa large intestinal roundworm

A
  • Eggs passed in faeces
  • Swalloed, hatch in duodenum as larvae
  • Larvae migrate through mucosa into blood
  • Larvae migrate into lung airspaces
  • Coughed up and swallowed
  • Adult worms develop in small intestine
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16
Q

What are the clinical presentations of Ascaris lumbricoides?

issa large intestinal roundworm

A
  • Allergic reactions (asthma, rashes, eosinophilia)
  • Cough
  • Fever
  • Severe pneumonitis
  • Abdominal pain
  • Peritonitis
  • Appendicitis
  • Mechanical blockage of intestine, pancreatic or bile ducts
17
Q

How to diagnose Ascaris lumbricoides?

issa large intestinal roundworm

A

Usually by visualising worms or eggs in faeces

18
Q

Pathogenesis of hookworms

A
  • Eggs in soil hatch and mature as larvae
  • Larvae penetrates skin
  • Migrate via bloodstream to lungs
  • Coughed up and swallowed
  • Adult worms develop in small intestine, blood sucking and lay eggs
19
Q

What are the clinical presentations of hookworms?

A
  • Hookworm anaemia
  • Severe anaemia: tiredness, pallor, oedema, heart failure
  • Note pale conjunctivae
  • Cutaenous larva migrans (most often caused by dog/cat hookworm): itchy rash lasts many weeks (treatable)
20
Q

How to diagnose hookworm?

A
  • Eggs in faeces
  • Worm
21
Q

Pathogenesis of Strongyloides stercoralis

A
  • Adult female in GIT produces eggs, develop into larvae in GIT and exit in faeces (mature into adults in soil, eggs, infectious larvae penetrate skin and migrate to GIT/some via lungs, coughed up and swallowed)
  • Autoinfection cycle
  • Some larvae produced from eggs in GIT become infectious (penetrate GIT mucosa/perianal skin, migrate to GIT)
  • Infection persists for decades (chronic gastrointestinal symptoms)
22
Q

What do immunocompromised patients suffer from Strongyloides stercoralis?

A

Immunocompromised patients may suffer overwhelming hyperinfection syndrome

23
Q

What does Strongyloides stercoralis hyperinfection syndrome cause?

A
  • Many systems may be involved as larvae migrate
  • Gastrointestinal: severe diarrhoea +/- blood, intestinal perforation, peritonitis, septicaemia
  • Pulmonary
  • Skin: Larva currens (very itchym lesions come and go over a few hours)
  • CNS: encephalitis, meningitis
24
Q

How to diagnose Strongyloides stercoralis?

A
  • Microscopy: larvae in stool, duodenal fluid, biopsy, sputum (not very sensitive, entero-test, USE PPE!!!)
  • PCR
  • Serology (does not distinguish current from old infection)
  • Screen patients from tropical countries before giving immune suppression (chemotherapy/transplants)
25
Q

Pathogenesis of Trichinella spiralis

A
  • Consumption of cysts in poorly cooked meat
  • Larvae released, penetrate intestinal mucosa, mature to adults
  • Adult worms copulate, female produces larvae which enter bloodstream
  • Larvae encyst in many tissues including striated muscle

Humans are dead-end host, no eggs

26
Q

What are the clinical presentations of Trichinella spiralis?

A
  • Most infections asymptomatic
  • Early: GIT symptoms, nausea, vomiting, diarrhoea
  • Many systems may be affected (muscular pain, facial swelling, heart damage, CNS symptoms: encephalitis, meningitis)
27
Q

Pathogenesis of Toxocara

A
  • Adult worm in dog/cat
  • Eggs in faeces
  • Human ingest eggs
  • Larvae hatch and invade through intestine wall

Humans are dead-end host

28
Q

What are the clinical presentations of Toxocara?

A
  • Retinal disease may cause blindness (ocular larva migrans)
  • Heavier infections: many organs involved (brain, lungs, liver: visceral larva migrans) -> fever, eosinophilia, hepatosplenomegaly, pneumonitis, convulsions
29
Q

How to diagnose Toxocara?

A

Serology - ELISA

30
Q
A

Parasites (5 decks)

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