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MOD II Exam II > Parasites > Flashcards

Parasites Flashcards

1
Q

What are the 3 protozoa of the intestinal tract?

A

Giardia lamblia
Entamoeba histolytica
Cryptosporidium

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2
Q

Mode of transmission for Giardia lamblia

A

Fecal-oral transmission of CYSTS

[Consuming water contaminated by animal/human feces in endemic areas; often associated with camping/traveling/hiking and not adequately purifying water before drinking it]

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3
Q

Clinical manifestations of Giardia lamblia

A

Bloating
Flatulence
Foul-smelling diarrhea (steatorrhea!)

Weight loss and potential ADEK vitamin deficiencies d/t malabsorption

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4
Q

Morphologic features and dx of Giardia lamblia

A

Distinct trophozoite shape with flagella

Dx by stool sample, immunoassay antigen, sanitation detection

Note that invasion is required for Giardia lamblia to cause diarrhea, so trophozoites found in stool is diagnostic of this parasite

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5
Q

What are the 2 life cycle stages of Entamoeba histolytica?

A

Cyst form: infectious if ingested

Trophozoite form: invasive, causes clinical manifestations

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6
Q

Describe transmission of Entamoeba histolytica

A

Ingestion in contaminated water (fecal-oral)

Associated with men who have sex with men d/t anal-oral transmission

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7
Q

Clinical manifestations caused by trophozoites of Entamoeba histolytica

A

Amoebic liver abscess affecting right lobe —> RUQ pain, hepatomegaly (abscess described as having anchovy-paste consistency)

Intestinal amoebiasis = “flask-shaped” ulcerations in colon; bloody diarrhea

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8
Q

Dx of Entamoeba histolytica

A

Stool sample — looking for cysts or trophozoites

Can also diagnose under a microscope if shown trophozoites with endocytosed RBCs; ELISA Ag test, serology, intestinal biopsy showing flask-shaped lesions in colon

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9
Q

Clinical manifestations of Cryptosporidium in healthy people vs. immunocompromised

A

Healthy: mild watery diarrhea

Immunocompromised: unrelenting watery diarrhea (note similar presentation in Isospora and Cyclospora in AIDS pts)

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10
Q

Transmission and pathogenesis of cryptosporidium

A

Fecal-oral transmission of oocyst

After ingestion, 4 motile sporozoites are released from oocyst and attach to small intestine wall causing damage and diarrhea

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11
Q

Dx of cryptosporidium

A

Stool sample for oocysts — stains acid-fast; cysts composed of 4 motile sporozoites

Small intestine biopsy

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12
Q

What are the 3 protozoa of the CNS?

A

Toxoplasma gondii
Trypanosoma brucei
Naegleria Fowleri

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13
Q

3 mechanisms of transmission of toxoplasma gondii

A
  1. Transplacental transfer
  2. Ingesting raw/undercooked pork containing cysts
  3. Ingesting water or undercooked veggies contaminated by animal stool (oocysts) — cat feces! - can also be inhalation

Note that pregnant women are at increased risk - should not clean litter box

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14
Q

Besides pregnant women, who else is at increased risk for toxoplasma gondii?

A

Immunocompromised (HIV pts) — CD4 < 100 and serology positive for IgG requires prophylaxis

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15
Q

Symptoms of adult toxoplasma gondii infection

A

Usually flu-like symptoms or asymptomatic in healthy people

Immunocompromised at risk for encephalitis, may see RING-ENHANCING lesions on head CT or MRI

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16
Q

Symptoms of congenital toxoplasmosis

A

Chorioretinitis
Hydrocephalus -> seizures
Intracranial calcifications

Can also cause deafness

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17
Q

Dx of toxoplasmosis

A

Serology (IgM and IgG), radiology, retinal exam

Can also do biopsy looking for intramuscular cysts

Note that serology does not indicate active infection, as 30% of population are estimated to be carriers

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18
Q

Vector and geographic distribution associated with Trypanosoma brucei

A

Vector = tsetse fly

Endemic to Gambia and Rhodesia, Africa (Trypanosoma brucei gambiense and Trypanosoma brucei rhodiense)

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19
Q

Clinical manifestations of Trypanosoma brucei infection

A

Causes African Sleeping Sickness

Initially presents as hard, red, painful ulcer that heals

Systemic spread presents as Winterbottom’s sign: fever, headache, dizziness, LAD

Patient goes through fever-free intervals followed by relapsing fever secondary to variable surface glycoprotein alterations

Eventual progression to daytime drowsiness, altered mental status, coma, and death = Demyelinating panencephalitis

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20
Q

Describe diagnosis and virulence factors associated with Trypanosoma brucei

A

Dx by trypanomastigotes in peripheral smear, lymph, or CSF

Can do card agglutination for T.brucei gambiense

T.brucei has variable surface glycoprotein coats that undergo constant antigenic variation = reason for relapsing fevers

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21
Q

Transmission of Naegleria fowleri

A

Associated with freshwater — swimming, watersports

Also associated with nasal irrigation, contact lens solutions, etc.

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22
Q

Pathogenesis and clinical manifestations of Naegleria fowleri

A

Trophozoite enters CNS via cribriform plate causing primary amoebic meningoencephalitis (nuchal rigidity, fevers, altered mental status)

High mortality rate — rapidly fatal with poor prognosis

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23
Q

Diagnosis of Naegleria Fowleri

A

CSF examination shows amoebas

[note that this may resemble a bacterial infection but there will be no bacteria on gram stain or culture. Note that NO cysts form in brain which differentiates NF from other amoebas]

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24
Q

What are the 4 protozoa of the blood

A

Trypanosoma cruzi
Babesia spp.
Plasmodium spp.
Leishmania spp.

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25
Q

Transmission of Trypanosoma cruzi including geographic location

A

Found in Southern US, Mexico, South America

Transmission via Reduviid “kissing bug” — bites around victim’s mouth and deposits feces (containing parasite) that are later scratched in

Note that initial bite is painless

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26
Q

Clinical manifestations of Chaga’s disease (Trypanosoma cruzi) — including 3 phases

A

Acute: chagoma, romana sign, fever, malaise, LAD, myocarditis, severe meningoencephalitis (young pts)

Intermediate: asymptomatic

Chronic: dilated cardiomyopathy, arrhythmia, megacolon, achalasia

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27
Q

Dx of Chaga’s disease

A

Peripheral smear for motile promastigotes (these are only present during active infection) — during chronic infection dx by serology and clinical symptoms

Trypanosomes may be seen within cardiac myocytes on heart biopsy (gets to heart by burrowing into endocarium)

Xenodiagnosis

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28
Q

Vector and geographic distribution of Babesia microti (babesiosis)

A

Vector = ixodes tick

Found in NE USA (similar to borrelia, so must check for that too)

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29
Q

Clinical manifestations of babesiosis

Who has increased risk besides immunocompromised?

A

Most cases subclinical or mild, but can look like malaria

In immunocompromised, see irregularly cycling fever, hemolytic anemia, fatigue, protracted disease course

Increased risk of severe disease in sickle cell patients as well as asplenic pts

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30
Q

Dx of babesiosis

A

Thick blood smear — see maltese cross appearance in RBC, representing TETRAD of trophozoites (this differentiates from malaria)

PCR is more sensitive test, can also do serology

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31
Q

A blood smear and ____ stain can be used to see parasites in RBCs infected with Plasmodium spp

A

Giemsa

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32
Q

What are the 4 species of Plasmodium and how are they characterized based on fever cycle

A

Plasmodium malariae = quartan fever cycle (q72 hrs)

Plasmodium vivax and Plasmodium ovale = tertian fever cycle (q48 hrs)

Plasmodium falciparum = irregular fever pattern

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33
Q

Which species of Plasmodium produces dormant hypnozoites in liver hepatocytes?

A

Plasmodium vivax

Plasmodium ovale

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34
Q

Clinical manifestations of Plasmodium falciparum

A

Irregular fever pattern
Cerebral malaria
Parasitized RBCs occlude vessels to kidneys and lungs

Banana-shaped on peripheral smear
Sickle cell disease is protective

35
Q

Life cycle of plasmodium

A

Anopheles mosquitos carry sporozoites in saliva which are transferred to humans

Sporozoites mature to trophozoites in liver, then become schizonts

Schizonts divide into merozoites which burst from hepatocytes and infect RBCs

The life cycle continues in RBCs: trophozoites —> schizonts —> merozoites —> infect RBCs

Note that immature schizont has “ring form “ inside an RBC

36
Q

Which life cycle form of plasmodium can form gametocytes, and is thus the form transferred from RBCs within mosquitos that spread infection from person to person?

A

Merozoites

[so merozoites are in RBCs, sporozoites are in mosquito saliva]

37
Q

Host, vector, and disease associated with Leishmania braziliensis

A

Host = vertebrates (carries amastigote within macrophages)

Vector = sandflies (carries promastigote - infectious form)

Disease: cutaneous Leishmaniasis

38
Q

Dx of cutaneous leishmaniasis (Leishmania braziliensis)

A

Microscopy — see darkly staining nuclei of multiple amastigotes in macrophages

39
Q

Disease and clinical manifestations of Leishmania donovani or chagasi

A

Visceral leishmaniasis - aka Black Fever or Kala-azar

Affects the bone marrow leading to pancytopenia — severe anemia; also causes fever, weakness, and massive splenomegaly

40
Q

Clinical manifestations of trichomonas vaginalis (STI)

A

Vaginitis = burning, itching, malodorous yellow-green discharge

Cervicitis (“strawberry cervix”) = erythematous with punctate hemorrhages

41
Q

Dx of Trichomonas vaginalis

A

Wet mount showing MOTILE trophozoites

Also note pH change of 4.5 and up

42
Q

What type of organism is Trichomonas vaginalis?

A

Protozoa

43
Q

What are the 5 intestinal nematodes

A 
Enterobius vermicularis
Ancyclostoma duodenale
Necator americanus
Strongyloides stercoralis
Trichinella spiralis
44
Q

What organism is associated with the following:

Female pin worm lays eggs at the anus, causing anal pruritis

Transmission is fecal-oral

Scotch tape test shows eggs under microscope

A

Enterobius vermicularis

45
Q

What are the hookworm nematodes? How are they obtained and what is their primary clinical manifestation?

A

Ancyclostoma duodenale and Necator americanus

Larvae penetrate skin on soles of feet —> bloodstream —> lungs —> GI tract

Cause iron deficiency anemia (microcytic/hypochromic)

46
Q

Dx of Ancyclostoma duodenale and Necator americanus

A

Check stool for eggs, sputum for larvae, eosinophilia

47
Q

Location and transmission of ascaris lumbricoides

A

Tropics and southern US

Ingestion of eggs from contaminated food (does NOT enter through skin)

48
Q

Clinical manifestations of ascaris lumbricoides

A

Can be asymptomatic but is more likely than other parasites to cause respiratory symptoms — dry cough

May accumulate enought to cause intestinal obstruction (often at ileocecal valve)

49
Q

Life cycle features and dx of ascaris lumbricoides

A

Infective eggs are swallowed and travel to intestine where they hatch. Larvae migrate to hepatic portal through intestinal wall, then enter lungs and alveolar spaces causing cough. Coughed up larvae are swallowed, and cycle continues

Dx by checking stool for eggs, sputum for larvae, eosinophilia

50
Q

Endemic areas, transmission, and pathogenesis of Strongyloides stercoralis

A

SE US, South America, sub-Saharan Africa, SE Asia

Larvae penetrate the skin on soles of feet —> bloodstream —> lungs —> GI tract (autoinfection — the larvae hatch from eggs laid in intestinal wall, repenetrate wall, and enter bloodstream)

51
Q

Dx of Strongyloides stercoralis

A

Stool for LARVAE (no eggs!)

Enterotest (nylon string), eosinophilia, Ab and Ag test

52
Q

Transmission and life cycle of trichinella spiralis

A

Cyst ingestion from raw pork, develop into larvae, larvae enter bloodstream, travel to striated muscle and form cysts within it

53
Q

Symptoms of Trichinella spiralis

A

Abdominal pain, vomiting, diarrhea, fever, severe myalgias, periorbital edema

Can invade heart and brain —> severe and possible fatality

54
Q

Dx of trichinella spiralis

A

Serologic test or muscle bioposy

Check CPK levels

55
Q

What parasite has a similar life cycle to enterobius, causes abdominal pain and diarrhea, is known as the whipworm, and is diagnosed by fecal exam for eggs as well as NO eosinophilia?

A

Trichuris trichiura

56
Q

5 tissue nematodes

A 
Dracunculus medinensis
Onchocerca volvulus
Wuchereria bancrofti
Toxocara canis
Loa Loa
57
Q

Location and transmission of Dracunculus medinensis

A

Africa — ghana and sudan

Drinking water contaminated with copepods (intermediate host) containing larvae

58
Q

Clinical features of dracunculus medinensis

A

Allergic symptoms — nausea, vomiting, hives, SOB; may see adult females emerge from painful ulcur in skin (LE)

Tx by stick and drag

59
Q

Location and vector associated with onchocerca volvulus

A

Africa, central, and south america

Black fly vector

60
Q

Clinical features and dx of onchocerca volvulus

A

“River Blindness” — caused by microfiliariae in the eye (slit lamp exam dx)

Onchodermatitis — caused by microfiliariae in intraepithelial granulomas — nodules and rash (hyper and hypopigmented spots)

61
Q

endemic areas and vector of Wuchereria bancrofti

A

Latin america, sub-saharan africa, SE asia

Vector = mosquito

62
Q

Clinical features and dx of Wuchereria bancrofti

A

Filarial fever — LAD, fever, HA, cough d/t microfiliariae in lungs

Chronic filiariasis — lymphedema, elephantitis

Dx by nocturnal blood draw (d/t nocturnal periodicity), Ag and Ab testing

63
Q

Describe the organism that causes visceral larva migrans

A

Dog hookworm

Ingestion of eggs via food contaminated by dog or cat feces

Causes toxocariasis: migration causes fever, wheezing, diarrhea, hepatitis, and chorioretinitis —> blindness

Dx by serology, eosinophilia

64
Q

Parasite that causes local subcutaneous swellings, show microfiliariae on blood smear, transmission via deer flies, and adult worms can be seen migrating across conjunctiva?

A

Loa Loa

65
Q

What is the difference between a cestode and a trematode?

A

Cestode = tapeworm

Trematode = flukes

66
Q

Species of platyhelminthes (flatworms)

A 
Shistosoma spp.
Taenia spp.
Diphyllobothrium latum
Hymenolepis nana
Echinococcus
67
Q

Species of Cestodes

A

Taenia saginata and solium
Diphyllobothrium latum
Echinococcus granulosus

68
Q

Species of trematodes

A

Schistosoma (mansoni, japonicum, haematobium)

Clonorchis sinensis

Paragonimus westermani

69
Q

Differentiate between T. saginata and T. solium

A

T. saginata intermediate host is cattle, while for T. solium it is pigs

T.solium also has hooks on proglottid heads, while saginata does not

70
Q

Clinical manifestations of Taenia infection (saginata or solium) based on ingestion of eggs vs. cysts vs. larvae

A

Ingestion of Taenia eggs in water contaminated by animal feces —> neurocysticercosis (seizures, hydrocephalus, swiss cheese head CT)

Ingestion of cysts or larvae —> taeniosis (usually asymptomatic but may cause GI problems or malabsorption)

71
Q

_____ is known as the fish tapeworm and is often obtained by ingestion of ____in sushi

A

Diphyllobothrium latum; larvae

72
Q

Symptoms and dx of Diphyllobothrium latum

A

Most are asymptomatic or non-specific. Causes diarrhea and is associated with B12 (cobalamin) deficiency - leading to megaloblastic macrocytic anemia

Dx by stool eggs or proglottids

73
Q

Host, transmission, and clinical features of echinococcus granulosus

A

Definitive host is dogs, intermediate host is sheep

Transmission is via dog feces

Causes hydatid cysts in liver — shows up as eggshell calcifications in cysts on liver CT

Cyst rupture —> anaphylaxis and acute abdomen

74
Q

Morphologic differences between schistosoma mansoni, japonicum, and haematobium

A

S.mansoni = eggs have large lateral spine

S.japonicum = eggs have small spine (appear round)

S.haematobium = large termal spine

75
Q

Transmission and life cycle of schistosoma

A

Swimmers at risk of infection d/t exposure to intermediate hosts — snails!

Adults mature in the liver, then migrate to other parts of the body; migration occurs against portal flow to get to venous destination

76
Q

Schistosoma are blood flukes, where is each species found geographically, and in the body?

A

S.mansoni = S.America and Africa, found in GI veins (feces)

S.japonicum = SE Asia, found in GI veins (feces)

S.haematobium = Africa, found in bladder veins (urine)

Note that mansoni and japonicum cause portal HTN, GI hemorrhage, abdominal pain, and eventual liver cirrhosis. Haematobium is characterized by hematuria and increased risk of bladder cancer

77
Q

T/F: schistosoma exhibit molecular mimicry

A

True

78
Q

What organism is characterized by the following:

Intermediate host snails transmit to fish consumed by humans; causes biliary fibrosis, cholangiocarcinoma, and pigmented gallstones, dx by operculated eggs on stool O and P

A

Clonorchis sinensis (chinese liver fluke)

79
Q

What organism is characterized by the following:

Chronic cough with bloody sputum, intermediate host snails, transmission via consumption of raw/undercooked crab meat containing larvae, and dx by operculated eggs on O and P

A

Paragonimus westermani

80
Q

Difference between larva currens and larva migrans

A

Larva currens = very FAST serpiginous eruption of S.stercoralis

Larva migrans = slow eruption, cutaneous caused by A.braziliense, visceral caused by T.canis

81
Q

Clinical features of schistosomiasis

A

Dermatitis - swimmers itch

Katayama fever = 4-8 wks - fever, hives, HA, weight loss, cough

Larva release eggs —> granuloma formation

Deposition in eggs: obstruction, inflammation, ulcers

(Dx by eggs in stool or urine, serology for Ab, eosinophilia)

82
Q

Hallmarks of prions

A

Long incubation
No host immune response (non-inflammatory)
Protease resistant

No gross neuro abnormalities. Exhibits microscopic spongiform changes, neuronal loss, and amyloid plaques

83
Q

Pathogenesis of prion disease

A

Alpha-helical PrPc may spontaneously shift to the beta-sheet PrPSc conformation. That PrPSc converts additional molecules of PrPc into PrPSc through physical interaction, eventually leading to formation of pathogenic PrPSc aggregates

Note Asparagine —> Valine conversion at position 129

MOD II Exam II (7 decks)

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