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Medical Parasitology > Lesson 2 - Nematodes > Flashcards

Lesson 2 - Nematodes Flashcards

Nematodes

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USMLE® Step 1 flashcards
1
Q

Common name: Giant Roundworm/Ascariasis

A

Ascaris lumbricoides

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2
Q

Most common and largest nematode. Soil-transmitted helminth (STH)

A

Ascaris lumbricoides

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3
Q

Habitat: small inestine

A

Ascaris lumbricoides / Necator americanus, Ancylostoma duodenale / Strongyloides stercoralis / Capillaria philippinensis

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4
Q

Transmitted by embryonated eggs (embryonated eggs are infective stage)

A

Ascaris lumbricoides

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5
Q

Diagnostic test for Ascaris lumbricoides

A
  • Direct fecal smear
  • Kato-katz technique
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6
Q

Pathogenesis:
- Major damage occurs during larval migration
- Principal site of tissue reaction is the lungs, where inflammation with an eosinophilic exudate occurs
- Heavy worm burden > malnutrition

A

Ascaris lumbricoides

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7
Q

Lung Phase (L3 > L5):
- Hypersensitivity pneumonutus (Loefeller’s Syndrome)

Intestinal phase (L5 > Adult Worm):
- acute intestinal obstruction
- malabsorption syndrome
- nutrient deficiencies

Wandering Worms:
- Due to erratic behavior of adult worms
- Hepatobiliary ascariasis
- Pancreatitis, appendicitis

A

Ascaris lumbricoides

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8
Q

Treatment of choice for Ascaris lumbricoides

A

Albendazole (has greater larvicidal activity than mebendazole)

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9
Q

Hookworm (Miner’s Anemia, “tunnel disease”, Wakana disease, “brickmaker’s anemia”, “Egyptian chlorosis”

A

Necator americanus / Ancylostoma duodenale

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10
Q

Soil-transmitted helminth (STH)
Blood-sucking nematodes
Differentiated based on character of buccal spsears of filariform larvae

A

Necator americanus / Ancylostoma duodenale

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11
Q

Transmission is by skin penetration by filariform larva (L3)

A

Necator americanus / Ancylostoma duodenale

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12
Q

Diagnostic Stage: Eggs in feces.

Diagnosed by:
- Direct fecal smear
- Kato-katz technique
- Harada-Mori culture

A

Necator americanus / Ancylostoma duodenale

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13
Q

The major damage is due to the loss of blood at the site of attachment in the small intestine (0.1 - 0.3 mL/worm/day).

Blood is consumed by the worm and oozes from the site in response to an anticoagulant made by the worm.

A

Necator americanus / Ancylostoma duodenale

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14
Q

Cutaneous phase:
- Penetration of L3 to the skin
- Ground itch
- Cutaneous larva migrans (creeping eruption)

Lung Phase:
- Lung migration of L3
- Simply Lung eosinophilia (Loeffler’s syndrome)

Intestinal Phase:
- L3 > L5
- Up to 200mL of blood may be lost per day. Iron deficiency (microcytic hypochromic) anemia - weakness and pallor
- Protein malnutrition (hypoalbuminemia)

A

Necator americanus / Ancylostoma duodenale

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15
Q

Treatment of choice for Necator americanus / Ancylostoma duodenale

A

Albendazole

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16
Q

Common name: Whipworm

A

Trichuris trichiura

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17
Q

Soil-transmitted helminth (STH)

Inhabits the large intestine. Transmitted by ingestion of embryonated eggs.

A

Trichuris trichiura

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18
Q

Diagnostic stage: unembryonated eggs

Diagnostic test:
- Direct fecal smear
- Kato-katz technique (lemon-shaped or barrel-shaped eggs with bipolar plugs/football-shaped eggs)

A

Trichuris trichiura

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19
Q

Burrow their hairlike anterior ends into the intestinal mucosa.

Does NOT cause significant anemia.

A

Trichuris trichiura

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20
Q

Symptoms:
- Diarrhea
- Rectal prolapse (from increased peristalsis to expel the worms)

A

Trichuris trichiura

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21
Q

Treatment for Trichuris trichiura

A

Mebendazole

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22
Q

Common name: Pinworm/Seatworm/Enterobiasis/Oxyuriasis

A

Enterobius vermicularis

23
Q

Soil-transmitted helminth (STH)
Life cycle is confined to humans.
MC STH in developed countries. A cosmopolitan worm.

Habitat: Large Intestine

A

Enterobius vermicularis

24
Q

Transmitted by ingestion of embryonated eggs

A

Enterobius vermicularis

25
Q

Diagnostic stage: Eggs on perianal folds.

Diagnostic test:
- Graham’s scotch / cellulose tape test (D-shaped ovum with thin colorless cell wall)

A

Enterobius vermicularis

26
Q

Female releases thousands of fertilized eggs on perianal skin

Eggs develop into larvae, causing anal pruritus.

Autoinfection can occur.

A

Enterobius vermicularis

27
Q

Spectrum of disease:
- Pruritus ani
- Eosinophlic enterocolitis
- Vulvovaginitis
- Salpingitis
- Appendicitis (oxuriasis)

A

Enterobius vermicularis

28
Q

Treatment of choice for Enterobius vermicularis

A

Pyrantel Pamoate

29
Q

Common name: Strongyloidiasis

A

Strongyloides stercoralis

30
Q

Soil-transmitted helminth (STH)

Facultative parasites

Only helminth that causes greater pathology in AIDS patients

A

Strongyloides stercoralis

31
Q

Transmitted by skin penetration of filariform larva (L3)

A

Strongyloides stercoralis

32
Q

Diagnostic stage: Rhabtidiform (L1)

Diagnostic Test:
- Harada-Mori culture
(distinguished by their prominent genital primordium and a pointed tail)

A

Strongyloides stercoralis

33
Q

Larvae penetrate intestinal wall directly without leaving host and migrate to the lungs (autoinfection)

A

Strongyloides stercoralis

34
Q

Cutaneous Phase:
- Penetration of L3 to the skin
- Acute: Ground Itch
- Chronic: serpiginous track (larva currens)

Lung Phase:
- Lung migration of L3
- Acute: Loeffler’s syndrome
- Chronic: Paradoxical asthma

Intestinal Phase:
- Mild watery diarrhea
- Burrowing into the mucosa and submucosa - ulceration and sloughing - duodenitis

Disseminated strongyloidiasis: hyperinfection syndrome (in immunocompromised)

A

Strongyloides stercoralis

35
Q

Common worm: Pudoc Worm / Capillariasis / Mystery Disease / Wasting Disease

A

Capillaria philippinensis

36
Q

Intestinal nematode
Only nematode whose life cycle involves a migratory bird

A

Capillaria philippinensis

37
Q

Transmitted by ingestion of infected fish with L3 larvae

A

Capillaria philippinensis

38
Q

Diagnostic stage: Unembryonated egg

Diagnostic test:
- Direct fecal smear
- Kato-katz technique (Peanut-shaped eggs with flattened bipolar plugs)

A

Capillaria philippinensis

38
Q

Embryonated eggs can cause autoinfection and hyperinfection

Ulcerative and compressive degeneration of enterocytes - severe malnutrition

A

Capillaria philippinensis

39
Q

Acute disease:
- Borborygmi - fever, abdominal pain, eosinophilia

Chronic disease:
- Chronic watery diarrhea
- Edema, wasting
- Protein-losing enteropathy
- Hypogammaglobulinemia

A

Capillaria philippinensis

40
Q

Treatment of choice for Capillaria philippinensis

A

Albendazole

41
Q

Disease: Filariasis
Blood and tissue nematode
Most delibitating nematode infection.

A

Wuchereria bancrofti / Brugia malayi

42
Q

Transmitted by mosquito bite. Infective stage: third-stage larva (L3)

Diagnostic stage: Microfilariae (L1)
Diagnostic test:
- Thick blood smear - curved or kinky microfilariae
- Specimen collection - best done at night between 8 PM and 4 AM - nocturnal periodicity
- DEC provocation test

A

Wuchereria bancrofti / Brugia malayi

43
Q

Pathogenesis: Adult worms in the lymph nodes > inflammation > lymphatic obstruction > lymphedema

A

Wuchereria bancrofti / Brugia malayi

44
Q

Acute disease:
- Acute adenolymphangitis
- Filarial fever
- Nocturnal wheezing (tropical pulmonary eosinophilia)
- Expatriate syndrome

Chronic disease:
- Hydrocele
- Elephantiasis
- Milky Urine (chyluria)

A

Wuchereria bancrofti / Brugia malayi

45
Q

Treatment of choice for Wuchereria bancrofti / Brugia malayi

A

Diethylcarbamazine

46
Q

Disease: Trichinosis

A

Trichinella spiralis

47
Q

Tissue nematode. IH: Pigs
Transmitted by undercooked pork. Infective & Diagnostic stage Encysted larvae.

A

Trichinella spiralis

48
Q

Diagnostic test:
- Muscle biopsy - most definitive; larvae within striated muscle
- Elevated CPKs
- Xenodiagnosis
- Bentonite Flocculation test

A

Trichinella spiralis

49
Q

Pathogenesis:
- Intestinal stage - liberated from pork by gastric juices
- Muscle stage - disseminated hematogenously to striated skeletal muscle > encysted within a host-derived cell (nurse cell)

A

Trichinella spiralis

50
Q

Mild Disease:
- Fever, muscle pain (myalgia)
- Periorbital edema
- Eosinophilia
- Hemorrhagic phenomena (subconjunctival splinter)

Severe Disease:
- Myocarditis
- Encephalitis
- Pneumonia
- Respiratory myositis

A

Trichinella spiralis

51
Q

Treatment of choice for Trichinella spiralis

A

Thiabendazole

52
Q

Found in: Sorsogon, Albay, Samar, Mindoro, Leyte, Marinduque, Palawan, Romblon, Camarines, All of Mindanao

A

Bancroftian Filariasis

53
Q
A

Medical Parasitology (3 decks)

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