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Parasitology > Week 4: Nematodes > Flashcards

Week 4: Nematodes Flashcards

1
Q

Where do nematodes typically infect?

A

Intestines
Blood and tissue

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2
Q

What are 3 main ways that nematodes are transmitted?

A
  1. Ingestion of embryonated eggs
  2. Direct penetration of skin by larvae
  3. Insect vector
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3
Q

From where do adult nematodes obtain food?

A
  • Partially digested intestinal contents
  • Ingesting blood
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4
Q

List intestinal nematodes

A
  1. Enterobius vermicularis (pinworm)
  2. Trichuris trichiura (whipworm)
  3. Ascaris lumbricoides (most common helminth infection)
  4. Necator americanus (hookworm)
  5. Ancylostoma duodenalae (hookworm)
  6. Strongyloides stercoralis (threadworm)
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5
Q

List blood and tissue nematodes

A
  1. Trichinella spiralis
  2. Dracunculus medinensis (Guinea worm)
  3. Filarial worms (there’s a bunch we need to know that I won’t include here to keep the flashcard shorter)
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6
Q

List clinically important microfilaria

A
  1. Wuchereria bancrofti
  2. Brugia malayi
  3. Loa loa
  4. Onchocerca volvulus
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7
Q

Describe the life cycle of Enterobius vermicularis (aka whipworm). Include infective and diagnostic stages

A
  1. Larvae inside eggs mature within 4-6 hrs. Located in perianal folds (is this the buttcrack??? I’m not googling this in class) Diagnostic stage
  2. Embryonated eggs ingested Infective stage
  3. Larvae hatch in small intestine
  4. Adults in lumen of cecum
  5. Gravid (female adult) migrates to perianal region at night to lay eggs
  6. Repeat cycle
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8
Q

Describe Enterobius vermicularis egg characteristics

A
  • Size: 50-60 by 20-30 microns
  • Thick, double-layered shell, flattened on one side
  • Larvae may be visible inside
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9
Q

Describe the Trichuris trichiura (whipworm) lifecycle. Include infective and diagnostic stages

A
  1. Diagnostic stage: Unembryonated eggs passed in feces
  2. 2- cell stage
  3. Advanced cleavage
  4. Infective stage: Embryonated eggs are ingested
  5. Larvae hatch in small intestines
  6. Adults in cecum
  7. Repeat cycle
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10
Q

Which laboratory diagnostic method do you use for Trichuris trichiura?

A

FEA concentration because found in stool

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11
Q

Describe Trichuris trichiura unembryonated egg characteristics

A
  • Size: 50-55 by 22-24 microns
  • Barrel-shaped, bile stained, thick shell, mucoid plugs at each end
  • You occasionally see adults in feces but mainly see egg stage
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12
Q

Describe the Ascaris lumbricoides life cycle. Include infective and diagnostic stages

A
  1. Diagnostic stage Adult worms in small intestine lay eggs that get passed in feces
  2. Infective stage: Fertilized eggs ingested
  3. Hatched larvae migrate and circulate to lungs
  4. coughed up and swallowed, so go to GI tract
  5. Repeat cycle
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13
Q

Why do these worms typically not cause symptoms? Mentioned in lecture, not in slides

A
  • Load may not be high enough
  • They’re happy enough to eat leftovers of what we humans eat
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14
Q

How do you diagnose Ascaris lumbricoides in the lab?

A
  • Preserve whole worm in formalin or 70-90% ethanol
  • Stool specimen for FEA concentration
  • Wet mount to look for eggs
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14
Q

Describe Ascaris lumbricoides adults

A
  • 6-12 inches in length
  • Live in small intestines but do NOT attach
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14
Q

Describe Ascaris lumbricoides fertilized eggs

A

See image

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15
Q

Describe Ascaris lumbricoides unfertilized eggs

A

See image

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16
Q

Describe the Necator americanus and Ancylostoma duodenalae hookworm life cycles. Include infective and diagnostic stages

A
  1. Diagnostic stage: Eggs passed in feces
  2. Rhabditiform larva hatches
  3. Filariform larva form
  4. Infective stage: Filariform larva penetrates skin
  5. Adults in small intestines
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17
Q

How do you diagnose hookworm in the laboratory?

A
  • Look for eggs in stool
  • FEA concentration
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18
Q

Describe hookworm eggs

A
  • Size: 60-75 by 35-40 microns
  • Oval-shaped
  • Smooth, thin shell
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19
Q

What kind of teeth Ancylostoma duodenale have?

A

Cutting teeth

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20
Q

What kind of teeth Necator americanus have?

A

Cutting plates

21
Q

Describe the Strongyloides stercoralis threadworm life cycle. Include infective and diagnostic stages

A

This is too wordy to type out. Please look at picture :D

Infective stage: filariform larvae
Diagnostic stage: rhabditiform larvae in feces

22
Q

How do you diagnose Strongyloides stercoralis in the lab?

A

ID rhabditiform larvae in feces, duodenal aspirate, or Entero-Test capsule

23
Describe *Strongyloides stercoralis* rhabditiform larvae
- Size: 200-300 microns long
24
How do you distinguish between *Strongyloides* and hookworm?
- Hookworm has longer buccal cavity - Hookworm has absent genital primordium BUT it's prominent in *Strongyloides* - Tail of hookworm is pointed, but *Strongyloides* has notched tail
25
Not question, but review
:)
26
Describe the *Trichinella spiralis* life cycle. **Include infective and diagnostic stages**
**Infective stage:** encysted larvae in undercooked meat ingested **Diagnostic Stage:** Larvae in striated muscle
27
What are the reservoir hosts for *Trichinella spiralis*?
Bears, rodents, and pigs!
28
How do you diagnose for *Trichinella spiralis* in the lab?
- Antibody detection (EIA) - Muscle biopsy (pathology does this)
29
Describe the *Dracunculus medinensis* Guinea worm life cycle. **Include infective and diagnostic stages**
**Infective stage:** Larvae in copepod ingested through contaminated water **Diagnostic stage:** Female emerging worm from skin; larvae escape blister and released into water
30
Describe the general filarial worm lifecycle. **Include infective and diagnostic stages**
**Infective stage:** Larvae in arthropod vector get passed to human through feeding site **Diagnostic stage:** Microfilariae in blood/tissue (such as dermis)
31
How do you diagnose filarial worms in the lab?
- ID through stained blood smear - ID in skin snip or tissue nodule
32
What type of disease manifestations are associated with *Wuchureria bancroftii* and *Brugia malayi*?
- Fever - Lymphangitis (lymphatic channel inflammation) - Elephantiasis
33
What type of disease manifestations are associated with *Loa loa*?
- Localized subcutaneous edema (aka Calabar swellings) - Eyeworm
34
What type of disease manifestations are associated with *Onchocerca volvulus*?
- River blindness - Fibrotic nodules on skin
35
Describe traits to look for in *Wuchereria bancrofti* (lymphatic)
- Sheath - No nuclei in the tip of tail
36
Describe traits to look for in *Brugi malayi* (lymphatic)
- Sheath - 2 distinct nuclei in the tip of the tail
37
Describe traits to look for in *Loa loa* (eye worm)
- Sheath - Nuclei extending to the tip of the tail
38
Describe traits to look for in *Onchocerca volvulus* (skin)
-No sheath - No nuclei in the tip of tail
39
Put it all together! What are the traits you look for in the different filiarial worms (sheath, nuclei)
:)
40
ID this intestinal nematode and stage
*Enterobius vermicularis* egg
41
ID this intestinal nematode and stage
*Trichuris trichiura* egg
42
ID this intestinal nematode and stage
*Ascaris lumbricoides* fertilized egg
43
ID this intestinal nematode and stage
*Ascaris lumbricoides* unfertilized egg
44
ID this intestinal nematode and stage
Hookworm egg
45
ID this intestinal nematode and stage
*Strongyloides stercoralis* rhabditiform larvae
46
ID this tissue nematode stage
*Trichinella spiralis* larvae
47
The pic is too gross to put here: but which blood/tissue nematode crawls out of your skin for the diagnostic stage?
*Dracunculus medinensis* AKA Guinea worm
48
ID the following filarial worm
*Wuchereria bancrofti*
49
ID the following filarial worm
*Brugia malayi*
50
ID the following filarial worm
*Loa loa*
51
ID the following filarial worm
*Loa loa*
52
ID the following filarial worm
*Onchocerca volvulus*

Parasitology (5 decks)

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