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Parasitology > Intestinal Nematodes > Flashcards

Intestinal Nematodes Flashcards

1
Q

Intestinal Nematodes

A

Known as Roundworms
Adult worms are long lived and survive in years
Anterior end has adaptations for attachment
Adult worms are both sexes
Males are usually smaller than female
Female may produce from few to 200,000 eggs/day
5 successive stages - four larval and adult worm
Most cases, 3rd stage larva is infective stage

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2
Q

Ascaris lumbricoides (large intestinal roundworm) General Information

A

Distributed worldwide in moist, warm climates, tropics and subtropics
Transmitted through ingestion of embryonated eggs from contaminated soil
Using human feces for fertilization of crops

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3
Q

Lifecylce of Ascaris lumbricoides

A

1) Eggs are ingested
2) Larvae hatch in duodenum (small intestine)
3) Larvae migrate to bronchial epithelium and cause damage
4) Larvae breakout into alveolar spaces
5) Larvae migrate up trachea and are swallowed
6) Adults mature in small intestine
7) Unembryonated eggs pass out in feces

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4
Q

Ascaris lumbricoides Adult Worm

A

Adults are white with thick cuticle that may become yellow from bile staining
Female:
- 20-35 cm long
- 5 mm in diameter
Male:
- 15-31 cm long
- More slender than female
- Curved Tail

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5
Q

Ascaris lumbroides Fertilized Egg

A
  • Round to Oval
  • 55-75 um x 35-50 um
  • Outer, Bile Stained, Albuminous coat
  • Thick Inner Hyaline Shell
  • Unsegmented Ovum when passed
  • Absence of fertile eggs means only females are present
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6
Q

Ascaris lumbricoides Unfertilized Egg

A
  • Barrel Shaped
  • 90-95 um x 43-47 um
  • Thinner and often indistinct
  • Mammillated layer varies from grossly irregular to relatively smooth
  • Internal contents are mass of disorganized, highly refractive granules
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7
Q

Ascaris lumbricoides Pathology

A

Dyspnea
Dry or productive cough
Wheezing or coarse rales
Fever
Transient eosinophilia
Itching of throat and chest

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8
Q

Ascaris lumbricoides Diagnostic Stage

A

1) Larval migration phase - larvae seen in sputum or gastic washings
2) Intestinal phase:
- Eggs or Adult worms in stool (fertile or infertile)
- Direct Wet Prep or Concentration

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9
Q

Ascaris lumbricoides Infectious Stage

A

Eggs

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10
Q

Enterobius vermicularis General Characteristics

A

Organism is cosmopolitan in distribution
More prevalent in temperate, cool climates
High prevalence in children

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11
Q

Enterobius vermicularis Transmission

A
  • Anus to mouth contamination, especially in children
  • Soiled night clothes and towels
  • Airborne eggs
  • Contaminated furniture, toys, and other objects
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12
Q

Enterobius vermicularis Life Cycle

A

1) Eggs are ingested
2) Larvae hatch in small intestine
3) Larvae migrate to colon
4) Adults mature in colon
5) Adults migrate out of anus
6) Adults lay eggs on perineum
7) Eggs embryonate on perineum
8) Eggs contaminate fingers

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13
Q

Enterobius vermicularis Adult

A

Female:
- 10 x 0.4 mm
- Fusiform body with long, thin pointed tail
Male:
- 3 x 0.15 mm
- Curled tail with copulatory apparatus

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14
Q

Enterobius vermicularis Egg

A
  • Oval, flattened on one side
  • 50-60 um x 25 um
  • Clear, colorless shell
  • Thick walled
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15
Q

Enterobius vermicularis Pathology

A
  • Slight irritation of intestinal mucosa
  • Nausea
  • Vomiting
  • Diarrhea
  • Pruritis (itching) caused by migration of female worm from anus to perianal region
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16
Q

Enterobius vermicularis Prevention

A
  • Improved personal and group hygiene
  • Children sleep in closed garments with short, clean fingernails
  • Dry heat used to sterilize
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17
Q

Enterobius vermicularis Diagnostic Stage

A

1) Detect eggs and/or adult worms by scotch tape prep
- Collect first thing in morning prior to showering or going to bathroom
2) Minimum 4-6 tapes required to rule out infection
3) Less than 5% of infections show eggs in stool

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18
Q

Trichuris trichiura General Characteristics

A
  • Distributed in tropics and subtropics
  • Children frequently pick up organism from contaminated soil
19
Q

Trichuris trichiura Life Cycle

A

1) Eggs are ingested
2) Larvae hatch in small intestines
3) Larvae migrate to colon
4) Adults mature in colon
5) Umembryonated eggs pass out in feces
6) Eggs embryonate in soil

20
Q

Trichuris trichiura Adult

A

Adult form is rarely recovered from stool due to firmly attaching to intestinal wall
Female:
- 40 mm in length
- long, slender esophageal region
Male:
- Smaller
- Coiled tail and copulating apparatus

21
Q

Trichuris trichiura egg

A

Barrel shape
50 um x 20 um
Bile stained
Have 2 shell membranes
Translucent polar plugs
Unsegmented ovum or embryo

22
Q

Trichuris trichiura Pathology

A

Asymptomatic or Symptomatic
Abdmoninal pain
Vomiting
Constipation
Fever
Distention of stomach and intestines
Flatulence
Heavy infections: bloody diarrhea, emaciation, prolapsed rectum

23
Q

Trichuris trichiura Diagnostic Stage

A

Recovery of eggs in direct wet prep or concentration
- Adult worms are rarely recovered

24
Q

Hookwork Generic Information

A

Ancylostoma duodenale (Old Work) and Necator americanus (New World)
- More common in the tropics and subtropics
- Worldwide about 900 million people carry

25
Q

Hookworm Life Cycle

A

1) Infection via filariform larvae from contaminated soil (larval migrans)
2) Migration via the lymphatics and blood stream to the heart and lungs
3) Penetrate the alveoli
4) Migrate up the trachea and are swallowed
5) Adult worm matures in the small intestines
6) Unembryonated eggs pass out in the feces
7) Eggs rapidly develop into rhabditiform larvae (hatch within 24-48 hrs)
8) Rhabditiform larvae molts twice to become filariform

26
Q

Necator americanus (New World Hookworm) adult

A

1) Female: 10 mm long, head end curved dorsally in hooked position
2) Male: 7-11 mm, posterior end forms copulating bursae
- Attaches to intestinal mucosa by two cutting plates (part of mouth)

27
Q

Ancylostoma duodenale (Old World) Hookworm adult

A

1) Female: head is not curved dorsally, slightly larger than Necator species
2) Male: smaller than female, terminates posteriorly with copulatory bursae
- Attaches to intestinal mucosa by a dual set of teeth

28
Q

Hookwork eggs

A
  • Eggs of two species are almost identical and not distinguishable
  • Oval with broad round ends
  • 40-70 um x 40 um
  • Thin clear, colorless shell
  • Clear space between developing embryo and thin shell
29
Q

Hookworm larvae

A
  • Long buccal cavity
  • Indistinct genital primordium, small and indistinct
  • Hour glass shaped esophugus
  • Pointed tail
30
Q

Hookworm Pathology

A

1) Pruritic dermatitis leading to vesicles due to larval skin penetration
2) Pneumonitis due to migration of larvae in lungs
3) Nonspecific gastrointestinal symptoms: intermittant abdominal pain, loss of appetite, and desire to eat soil (gephagy) due to presence of adults
- In acute phase: increased peripheral eosinophilia
- In chronic phase: develop Fe deficiency anemia
4) Hypoalbuminemia
5) Diarrhea with black to red stools

31
Q

Hookworm Diagnostic Stage

A

1) Recover and identify eggs in feces (direct and concentrate sediment)
2) If stool remains unpreserved for over 24 hrs, larvae may be seen. Differentiate from Strongyloids species

32
Q

Stronglyoides stercoralis General Information

A
  • Organism distributed worldwide
  • Prefers warm, moist climates due to greater fraility of filariform larvae
33
Q

Strongyloides stercoralis Life Cycle

A

Very similar to Hookworm, except eggs hatch in intestines and the L2 larvae are passed in feces

34
Q

Strongyloides stercoralis adult

A

1) Female: small, slender 2 mm
2) Male: thought to have extremely short life span and not observed in humans

35
Q

Strongyloides stercoralis egg

A

1) 50 um x 32 um
2) Similar to but smaller than hookworm eggs
3) Ova cannot be distinguished from hookworm
4) Clear thin shell
5) May be seen in diarrhic stool

36
Q

Strongyloides stercoralis Larvae

A

1) Develops into filariform larvae in soil
2) 700 um in length
3) Short buccal cavity
4) Prominent genital primordium
5) Notched tail

37
Q

Strongyloides stercoralis Pathology

A

Three areas of primary involvement
- Cutaneous skin itching
- Lungs - dyspnea and malaise
- Intestinal - pain, nausea, vomiting, diarrhea
Autoinfecion - long term immunocompromised, pneumonitis, and eosinophilia

38
Q

Strongyloides stercoralis Diagnostic Stage

A
  • Recovery and identification of larval stages in feces
  • Rarely see embryonated eggs in stool unless highly diarrhic stool
  • String test has been used to recover this organism
39
Q

Enterobius vermicularis Common name

A

Pinworm

40
Q

Enterobius Infectious Stage

A

Eggs

41
Q

Trichuris trichiura Common name

A

Whipworm

42
Q

Trichuris trichiura Infectious Stage

A

Egg

43
Q

Hookworm Infectious Stage

A

Filariform Larvae

44
Q

Strongyloides stercoralis Infectious Stage

A

Filariform Larvae

Parasitology (8 decks)

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