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Tim's CP Board Review > Parasitology > Flashcards

Parasitology Flashcards

1
Q

Giardia - Morphology

A

Trophozoite: Pear shaped, with two nuclei and 4 pairs of flagellae
Cyst: 4 nuclei

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2
Q

Chilomastix

A

Non-pathogenic.

Trophozoite: Pear-shaped, flagellated. One nucleus, with adjacent cytostome

Cyst: Lemon-shaped with anterior hyaline knob. “Shepherd’s hook”

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3
Q

Dientamoeba

A

Non-pathogenic.

Only trophozoite: 1-2 nuclei, each with 4 clumps of chromatin (resembles die pips)

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4
Q

Entamoeba histolytica

A

Fecal-oral cyst transmission. Causes amebic dysentery, sometimes liver abscesses.

Cyst: 1-4 nuclei, with “chromatoid bar” cigar-shape

Trophozoite: 1 nucleus with central karyosome. RBCs!

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5
Q

Entamoeba dispar

A

Non-pathogenic; resembles E. Histolytica except without erythrophagocytosis.

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6
Q

Entamoeba hartmannii

A

Resembles E. Histolytica, only smaller (<9um)

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7
Q

Entamoeba coli

A

Resembles entamoeba histolytica, except larger, has 1-8 nuclei, and eccentric karyosome

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8
Q

Iodamoeba butschlii

A

Cyst has large central glycogen vacuole and one nucleus.

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9
Q

Blastocystis

A

Unclear pathogen status

Huge central vacuole, compresses nuclei peripherally

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10
Q

Cryptosporidium parvum

A

Fecal-oral oocyst, immediately infective. Resists chlorine.

Tiny (1-3um), acid-fast. Diagnosable with histology.

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11
Q

Cyclospora

A

Fecal-oral oocyst, delayed infectivity. Resists chlorine.

8-10um, modified acid-fast. Thick wall?

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12
Q

Cystisospora

A

Fecal-oral oocyst (delayed infectivity). Rare.

The only oocyst that can be observed on O&P. Round/ovoid with 2 sporozoites. 20-33um?

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13
Q

Microsporidia

A

Protozoan (or fungus) that is actually an enormous phylum of OBLIGATE INTRACELLULAR parasites.

Best diagnosed on histology. “Belt-like stripe”

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14
Q

Malaria transmission & diagnosis

A

Transmitted by anopheline mosquitoes, transmission, needles, or vertically

Diagnosed by BinaxNow (rapid Ag; has T1 for falciparum, T2 for common plasmodium antigen), 200-300 thick smear fields (but use thin smear to quantify).

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15
Q

Plasmodium falciparum

A

Malignant tertian fever (48 hours). Cerebral symptoms, often fatal.

High parasitemia, including multiple organisms per RBC (all stages). Crescent (“banana”) gametocytes (DO NOT COUNT TOWARDS PARASITEMIA LOAD). No schizonts.

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16
Q

Plasmodium malariae

A

Causes quartan (72hr) fever. Mild? Indolent.

Infects mature RBCs (smaller). 6-12 merozoites.

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17
Q

Plasmodium vivax

A

Schizont can infect liver&raquo_space; hypnozoites cause true dormancy & relapses.

Infects reticulocytes (larger). Schuffner stippling. 12-24 merozoites, ameboid trophozoite.

Most common malaria overall

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18
Q

Plasmodium ovale

A

Schizont can infect liver&raquo_space; hypnozoites cause true dormancy & relapses.

Infects reticulocytes (larger). Schuffner stippling. Up to 16 merozoites.

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19
Q

Plasmodium knowlesi

A

Zoonotic (often infects rhesus monkeys). Asia.

Morphologically indistinguishable from P. Malariae, but clinically worse.

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20
Q

Babesia microti

A

Ixodes tick (NE US / anterior anal groove). 1-4wk incubation&raquo_space; malaria-like illness. TTI.

Maltese cross, ring forms, extracellular merozoites.

Dx: Serology, smear, PCR

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21
Q

Trypanosoma brucei

A

Transmitted by Tsetse (Glossina) fly. Rhodesiense (west), Gambiense (east)

Triphasic disease: Chancre&raquo_space; Hemolymphatic involvement&raquo_space; CNS involvement (fatal)

Large trypomastigotes with SMALL POSTERIOR KINETOPLAST and dividing forms

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22
Q

Trypanosoma Cruzi

A

Transmitted by Reduviid bug.

Chagoma / Romana&raquo_space; Systemic symptoms including megacolon/megaesophagus and cardiomyopathy.

Amastigotes on tissue sections. Trypomastigote on smear with LARGE SUBTERMINAL KINETOPLAST and no dividing.

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23
Q

Leishmania donovani

A

Transmitted by sandfly. Promastigote transforms to amastigote within macrophages.

Cutaneous ulcer&raquo_space; visceral involvement (especially in immunocompromised)

Resembles histoplasmosis. Look for kinetoplast. No budding, no PAS.

24
Q

Toxoplasma Gondii

A

Cats, infected meat, transplacental, transfusion. Direct transmission of oocyst.

Immunocompetent: Asymptomatic, sometimes mono-like.
Immunocompromised: Ring-like brain abscesses, carditis.
Congenital: Severe chorioretinitis, hydrocephalus with calcifications, death.

Dx with serology (follow IgM to seroconversion). Cysts with bradyzoites on H&E. Tachyzoites indicate active infection.

25
Q

Trichomonas

A

1 STD. Underrecognized. Only trophozoite (no cysts)

Undulating membrane covers 1/2 of body. 1 nucleus.

26
Q

What features are common to all nematodes?

A

True gut (coelom) and cuticle.

Most cause high morbidity but low mortality infections.

27
Q

Enterobius vermicularis (pinworm)

A

1 nematode in US. Children, often autoinfection.

No O&P. Eggs are oval, 50-60um, asymmetric.

Can directly observe worms at night.

28
Q

Trichuris trichiura (whipworm)

A

Fecal-oral transmission. Produces 1000s of eggs per day.

May cause prolapse with severe burden.

Ova are barrel-shaped, brown, with bipolar mucus plugs.

29
Q

Ascaris lumbricoides

A

1 nematode worldwide. Fecal-oral egg transmission but lung maturation (eosinophilic pneumonitis). 100,000s of eggs.

Huge worms (up to 40cm), often many&raquo_space; obstruction, perforation.

Ova: Unfertilized are mammillated/bumpy. Fertilized are round with ruffled shell.

30
Q

Necator/Ancylostoma (hookworms)

A

Skin-penetrating filaria (larva migrans)&raquo_space; lung maturation (eosinophilic pneumonitis).

Causes severe iron deficiency anemia.

Ova are ~65um with early embryo inside (grape-like).
*Cannot differentiate species by eggs; but ancylostoma has “4 fangs” while necator has “2 plates”

31
Q

Strongyloides

A

Skin-penetrating filaria (larva migrans)&raquo_space; lung maturation (eosinophilic pneumonitis). Autoinfection!

Adults 2mm long; rhabditiforms in stool. Can move on agar plate&raquo_space; may “carry” gram-neg bacteria in disseminated infection

Dx by O&P, serology, often histology.

32
Q

Wuchereria Bancrofti

A

Many vectors (Culex, Anopheles). Causes lymphedema, elephantiasis.

Pulmonary tropical eosinophilia syndrome.

Nighttime collection&raquo_space; Sheathed worm with nuclei that do not extend to tail.

33
Q

Brugia

A

Many vectors (Culex, Anopheles). Causes lymphedema, elephantiasis.

Pulmonary tropical eosinophilia syndrome.

Nighttime collection&raquo_space; Sheathed worm with 2 terminal nuclei

34
Q

Loa loa filariasis

A

Horse/deer fly vector. Occupies visceral lymphatics?

Worm classically infects conjunctivae. Periocular “Calabar swelling”

Nighttime harvest&raquo_space; Sheathed worm with nuclei that extend to end of tail.

35
Q

Onchocerciasis

A

Transmitted by black fly.

Subcutaneous nodules, river blindness.

No specific harvest-time&raquo_space; Unsheathed worm that does not have nuclei to end of tail

36
Q

Diphyllobothrium latum

A

Fish tapeworm, huge. “Bothrium” folded scolex. 1Mil eggs/day!

Proglottids are wider than long.

Ova have operculum and abopercular knob. 70um.

37
Q

Taenia solium

A

Pig tapeworm. Can cause neurocysticercosis (egg ingestion) or GI parasite (larva ingestion).

Proglottids have 7-13 uterine branches per side.

Eggs are 30um, round, with thick shell and visible hooklets.

38
Q

Taenia saginata

A

Beef tapeworm.

Proglottids have 15-30 uterine branches per side.

Eggs are 30um, round, with thick shell and visible hooklets.

39
Q

Echinococcus granulosis

A

Infects sheep & dogs (humans incidental). Actually a tiny cestode (3 segments).

Hydatid cysts are thick-walled with scolical debris.

Risk of anaphylaxis&raquo_space; inject and aspirate.

40
Q

Echinococcus multilocularis

A

Rats, rodents etc. Humans incidental host.

More severe liver cyst burden than granulosus…

41
Q

Hymenolepis nana & diminuta (dwarf tapeworm)

A

1 cestode in US.

Nana: Worms are 4cm long. Ova have thick shell with polar filaments (“silly string”)
Diminuta: No polar filaments

42
Q

Dipylidium caninum

A

Dogs & cats. “Rice-grain” proglottids in stool.

Ova are actually packets/sachets of 5-15 eggs.

43
Q

What are some general characteristics of trematodes?

A

Flatworms; have ventral sucker and oral cavity with no true coelom. All are hermaphroditic and rely on 1-2 intermediate hosts, of which one is always a snail.

44
Q

Clonorchis sinensis

A

Asia, uncooked fish secondary (smoking, pickling do not kill).

Bile duct obstruction, cholangiocarcinoma…

Ova have operculum and abopercular knob with shoulders. 30um.

45
Q

Fasciola hepatica

A

Raw water cress. Bile duct obstruction.

Small operculum, no shoulders. 140um.

46
Q

Fasciolopsis buski

A

Raw water chestnut. Bile duct obstruction.

Small operculum, no shoulders. 140um.

47
Q

Paragonimus Westermani

A

Oriental lung fluke; crayfish/crab.

Acute infection involves GI but chronic infection involves lungs.

Ova have operculum, thickened abopercular end. 100um.

48
Q

Schistosoma mansoni

A

Colon polyposis, bloody diarrhea, portal HTN.

Prominent lateral spine, 120um.

49
Q

Schistosoma japonicum

A

Portal hypertension.

Small-round ova with wimpy lateral spine (80um)

50
Q

Schistosoma hematobium

A

Cystitis, squamous metaplasia, urothelial carcinoma.

Terminal spine. 120um.

51
Q

Balantidium coli

A

The only ciliated parasite of humans. Quite large (70um). Pigs.

52
Q

Ixodes tick

A

Anterior anal groove

Transmits borrelia, anaplasma

53
Q

Stool preservatives

A

Sodium acetate / acetic acid / formalin (SAF)

Polyvinyl alcohol (PVA)

Merthiolate iodine formalin (MIF)

54
Q

Blood smear preservative

A

Use EDTA (heparin distorts morphology)

55
Q

Trichinella

A

Pork-encysted larvae&raquo_space; adult worms in human GI tract&raquo_space; larvae re-encyst. One host with no eggs!

GI symptoms, muscle pain/weakness, fever, periorbital edema.

Diagnosed with serology or H&E.

56
Q

Acanthamoeba

A

Wrinkled double-wall. Causes keratitis and granulomatous encephalitis.

Tim's CP Board Review (16 decks)

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