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MOD II Exam II > Parasites > Flashcards

Parasites Flashcards

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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
Transmission of Trypanosoma cruzi including geographic location
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
26
Clinical manifestations of Chaga’s disease (Trypanosoma cruzi) — including 3 phases
Acute: chagoma, romana sign, fever, malaise, LAD, myocarditis, severe meningoencephalitis (young pts) Intermediate: asymptomatic Chronic: dilated cardiomyopathy, arrhythmia, megacolon, achalasia
27
Dx of Chaga’s disease
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
28
Vector and geographic distribution of Babesia microti (babesiosis)
Vector = ixodes tick Found in NE USA (similar to borrelia, so must check for that too)
29
Clinical manifestations of babesiosis Who has increased risk besides immunocompromised?
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
30
Dx of babesiosis
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
31
A blood smear and ____ stain can be used to see parasites in RBCs infected with Plasmodium spp
Giemsa
32
What are the 4 species of Plasmodium and how are they characterized based on fever cycle
Plasmodium malariae = quartan fever cycle (q72 hrs) Plasmodium vivax and Plasmodium ovale = tertian fever cycle (q48 hrs) Plasmodium falciparum = irregular fever pattern
33
Which species of Plasmodium produces dormant hypnozoites in liver hepatocytes?
Plasmodium vivax | Plasmodium ovale
34
Clinical manifestations of Plasmodium falciparum
Irregular fever pattern Cerebral malaria Parasitized RBCs occlude vessels to kidneys and lungs Banana-shaped on peripheral smear Sickle cell disease is protective
35
Life cycle of plasmodium
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
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?
Merozoites [so merozoites are in RBCs, sporozoites are in mosquito saliva]
37
Host, vector, and disease associated with Leishmania braziliensis
Host = vertebrates (carries amastigote within macrophages) Vector = sandflies (carries promastigote - infectious form) Disease: cutaneous Leishmaniasis
38
Dx of cutaneous leishmaniasis (Leishmania braziliensis)
Microscopy — see darkly staining nuclei of multiple amastigotes in macrophages
39
Disease and clinical manifestations of Leishmania donovani or chagasi
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
Clinical manifestations of trichomonas vaginalis (STI)
Vaginitis = burning, itching, malodorous yellow-green discharge Cervicitis (“strawberry cervix”) = erythematous with punctate hemorrhages
41
Dx of Trichomonas vaginalis
Wet mount showing MOTILE trophozoites Also note pH change of 4.5 and up
42
What type of organism is Trichomonas vaginalis?
Protozoa
43
What are the 5 intestinal nematodes
``` Enterobius vermicularis Ancyclostoma duodenale Necator americanus Strongyloides stercoralis Trichinella spiralis ```
44
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
Enterobius vermicularis
45
What are the hookworm nematodes? How are they obtained and what is their primary clinical manifestation?
Ancyclostoma duodenale and Necator americanus Larvae penetrate skin on soles of feet —> bloodstream —> lungs —> GI tract Cause iron deficiency anemia (microcytic/hypochromic)
46
Dx of Ancyclostoma duodenale and Necator americanus
Check stool for eggs, sputum for larvae, eosinophilia
47
Location and transmission of ascaris lumbricoides
Tropics and southern US Ingestion of eggs from contaminated food (does NOT enter through skin)
48
Clinical manifestations of ascaris lumbricoides
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
Life cycle features and dx of ascaris lumbricoides
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
Endemic areas, transmission, and pathogenesis of Strongyloides stercoralis
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
Dx of Strongyloides stercoralis
Stool for LARVAE (no eggs!) Enterotest (nylon string), eosinophilia, Ab and Ag test
52
Transmission and life cycle of trichinella spiralis
Cyst ingestion from raw pork, develop into larvae, larvae enter bloodstream, travel to striated muscle and form cysts within it
53
Symptoms of Trichinella spiralis
Abdominal pain, vomiting, diarrhea, fever, severe myalgias, periorbital edema Can invade heart and brain —> severe and possible fatality
54
Dx of trichinella spiralis
Serologic test or muscle bioposy Check CPK levels
55
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?
Trichuris trichiura
56
5 tissue nematodes
``` Dracunculus medinensis Onchocerca volvulus Wuchereria bancrofti Toxocara canis Loa Loa ```
57
Location and transmission of Dracunculus medinensis
Africa — ghana and sudan Drinking water contaminated with copepods (intermediate host) containing larvae
58
Clinical features of dracunculus medinensis
Allergic symptoms — nausea, vomiting, hives, SOB; may see adult females emerge from painful ulcur in skin (LE) Tx by stick and drag
59
Location and vector associated with onchocerca volvulus
Africa, central, and south america Black fly vector
60
Clinical features and dx of onchocerca volvulus
“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
endemic areas and vector of Wuchereria bancrofti
Latin america, sub-saharan africa, SE asia Vector = mosquito
62
Clinical features and dx of Wuchereria bancrofti
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
Describe the organism that causes visceral larva migrans
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
Parasite that causes local subcutaneous swellings, show microfiliariae on blood smear, transmission via deer flies, and adult worms can be seen migrating across conjunctiva?
Loa Loa
65
What is the difference between a cestode and a trematode?
Cestode = tapeworm Trematode = flukes
66
Species of platyhelminthes (flatworms)
``` Shistosoma spp. Taenia spp. Diphyllobothrium latum Hymenolepis nana Echinococcus ```
67
Species of Cestodes
Taenia saginata and solium Diphyllobothrium latum Echinococcus granulosus
68
Species of trematodes
Schistosoma (mansoni, japonicum, haematobium) Clonorchis sinensis Paragonimus westermani
69
Differentiate between T. saginata and T. solium
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
Clinical manifestations of Taenia infection (saginata or solium) based on ingestion of eggs vs. cysts vs. larvae
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
_____ is known as the fish tapeworm and is often obtained by ingestion of ____in sushi
Diphyllobothrium latum; larvae
72
Symptoms and dx of Diphyllobothrium latum
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
Host, transmission, and clinical features of echinococcus granulosus
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
Morphologic differences between schistosoma mansoni, japonicum, and haematobium
S.mansoni = eggs have large lateral spine S.japonicum = eggs have small spine (appear round) S.haematobium = large termal spine
75
Transmission and life cycle of schistosoma
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
Schistosoma are blood flukes, where is each species found geographically, and in the body?
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
T/F: schistosoma exhibit molecular mimicry
True
78
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
Clonorchis sinensis (chinese liver fluke)
79
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
Paragonimus westermani
80
Difference between larva currens and larva migrans
Larva currens = very FAST serpiginous eruption of S.stercoralis Larva migrans = slow eruption, cutaneous caused by A.braziliense, visceral caused by T.canis
81
Clinical features of schistosomiasis
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
Hallmarks of prions
Long incubation No host immune response (non-inflammatory) Protease resistant No gross neuro abnormalities. Exhibits microscopic spongiform changes, neuronal loss, and amyloid plaques
83
Pathogenesis of prion disease
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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