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MOD (Mechanisms of Disease) Exam 3 > Parasites and Prions > Flashcards

Parasites and Prions Flashcards

1
Q

Giardia Lamblia: who is affected, how do they get the parasite, and what GI problems does the parasite cause?

A
  • seen in hikers who drink unfiltered, contaminated water (fecal oral transmission)
  • infectious cysts are passed on in stool; use O&P to diagnose (flagellated, pear-shaped trophozoites)
  • causes bloating, farting, and foul smelling diarrhea (steatorrhea from GI malabsorption)
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2
Q

Entamoeba histolytica: who is affected, how do they get the parasite, and what two GI problems does this parasite cause?

A
  • seen in people who eat/drink contaminated products or men-men sexual relations
  • infectious cysts are passed in stool; use O&P to diagnose (endocytosed RBCs in trophazoite)
  • causes right liver lobe abscess (RUQ pain) having “anchovy paste” consistency
  • causes focal intestinal mucosa ulcerations (flask-shaped) = BLOODY DIARRHEA
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3
Q

Cryptosporidium: who is affected, how do they get the parasite, and what GI problems does the parasite cause?

A
  • seen in HIV patients (immunocompromised); composed of 4 motile sporozoites (damage small int.)
  • infectious cysts passed in stool; stain ACID-FAST
  • causes copious watery diarrhea (highly resistant to chlorination but oocysts can be filtered out of water)
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4
Q

Toxoplasma Gondii: who is affected, how do they get the parasite, and what two CNS problems does the parasite cause in the immunocompromised?

A
  • pregnant women and immunocompromised at inc. risk of contracting
  • oocysts transferred via CAT FECES (definitive hosts), but can also be found in undercooked meats
  • causes ring-enhancing lesions on MRI (HIV pts) and ENCEPHALITIS (most common presentation)
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5
Q

What are 4 symptoms of congenital Toxoplasmic infection? How would you differentiate Toxoplasma from CNS lymphoma?

A
  • TORCH INFECTION causing intracranial calcifications, hydrocephalus, seizures, chorioretinitis, hearing loss
  • Toxoplasma has MULTIPLE ring-enhancing lesions vs CNS lymphoma which has a solitary ring-enhancing lesion on CT/MRI
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6
Q

Trypanosoma brucei (African Sleeping Sickness): what carries the parasite, what does the parasite look like, and what are 4 CNS problems that the parasite can cause?

A
  • caused by tsetse fly bites (Gambia/Rhodesia) and causes coma (potentially death if untreated); variable surface glycoproteins (antigenic variation)
  • trypomastigotes seen on blood smear (LN/CSF): protozoa are motile w/SINGLE FLAGELLA
  • post. cervical lymphadenopathy (early), axillary lymphadenopathy, recurrent fevers, coma
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7
Q

Naegleria fowleri: what 3 things can this parasite be found in and what is the major CNS problem it causes?

A
  • found in freshwater (watersports) and trophozoites enter CNS via cribiform plate; also seen in contaminated lens solution and nasal irrigation
  • cause Primary Amoebal Meningoencephalitis (fatal) –> use CSF to diagnose
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8
Q

Trypanosoma cruzi (Chagas Disease): who is affected, what 3 clinical findings does the parasite cause, and what are two visual diagnostic findings?

A
  • blood protozoa
  • “kissing bug” bites around mouth contaminated with feces that can be scratched into skin (reduviid); mainly in South and Central America
  • causes megacolon, dilated cardiomyopathy, megaesophagus
  • see trypomastigotes (blood-form) on peripheral smear and trypanosomes in cardiac myocytes on biopsy (burrows into endocardium)
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9
Q

Babesia: what carries the parasite and where is it located, what does the parasite look like, and what are 3 clinical findings of the parasite?

A
  • blood protozoa introduced by saliva of Ixodes or “Deer” tick in Northeastern US; thick blood smear shows “Maltese Cross” in RBCs
  • causes hemolytic anemia, jaundice, irregular cycling fevers
  • inc. risk of disease in sickle cell pts and asplenic pts
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10
Q

Plasmodium malariae, ovale/vivax, and falciparum: what do they look like and what is the general fever pattern for each of the 3 groups?

A
  • blood protozoa seen on thick blood smear w/Giemsa stain

PM: quartan fever (72 hours)

PO/V: dormant hypnozoites in LIVER
- tertian fever (48 hrs)

PF: irregular fever pattern (MOST SEVERE FORM)

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11
Q

Plasmodium falciparum: what does it look like, what 3 clinical findings does it cause, and what condition can protect from it?

A
  • gametocytes appear banana-shaped on blood smear
  • occludes brain capillaries (CEREBRAL MALARIA), occludes kidney capillaries, occludes lung capillaries
  • sickle cell anemia protects pts from this condition
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12
Q

How is the Plasmodium parasite introduced into victims and what is its life cycle like?

A
  • Anopheles mosquito saliva introduces sporozoites into blood (mature to merozoites in LIVER)
  • merozoites rupture from shizonts and hepatocytes, and infect RBCs in the bloodstream (trophozoites look like rings in RBCs)
  • can initiate sexual development through gametocytes
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13
Q

Leishmania brazillensis and donovani: what does the parasite look like and what are the clinical appearances of both types?

A
  • blood protozoan; numerous amastigotes nuclei (non-flagellated) seen in macrophages

LB: hosted by vertebrates and transferred by Sand Flies; causes cutaneous leishmaniasis (papules/lesions –> ulcerative lesions)

LD: causes visceral leishmaniasis (black fever or kala-azar); spiking fever, pancytopenia, hepatosplenomegaly

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14
Q

Trichomonas vaginalis: what is it, what does it look like, and what are 4 clinical findings of the parasite?

A
  • sexually transmitted protozoa
  • motile trophozites on wet mount, pH > 4.5
  • causes “strawberry” cervix w/burning, itching, and frothy yellow/green malodorous discharge
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15
Q

Enterobius Vermicularis (Pinworm): how are they transmitted and how can you diagnose?

A
  • intestinal nematodes mainly affecting children through fecal-oral transmission (itching butt)
  • females lay eggs at anus
  • diagnosed with Scotch Tape over the anus
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16
Q

Ancyclostoma duodenale and Necator americanus (Hookworm): how are they transmitted, what clinical finding do they cause, and how can they be diagnosed?

A
  • intestinal nematodes found in Southern rural US that are transmitted by walking barefoot (penetrate skin)
  • travel through blood vessels to the lungs, then back to GI tract
  • cause Iron Deficiency Anemia and can be diagnosed by finding eggs in stool and inc. eosinophilic count
17
Q

Ascaris Lumbricoides (Large Roundworm): how is it transmitted, what 3 clinical findings does it cause, and how can it be diagnosed?

A
  • intestinal nematodes transmitted via eggs in contaminated water and food
  • travel through blood vessels to lungs, then back to GI tract
  • cause malnutrition and respiratory problems and INTESTINAL OBSTRUCTION @ ileocecal valve
  • diagnose via eggs in stool and inc. eosinophilic count
18
Q

Strongyloides stercoralis: how is it transmitted and how can it be diagnosed?

A
  • intestinal nematode that penetrates skin of foot and travels through the blood vessels to the lungs, then back to the GI tract
  • can AUTOINFECT GI tract after larvae hatch
  • diagnose via LARVAE in stool and inc. eosinophilic count
19
Q

Trichinella spiralis: what is the parasite found in and what are 5 clinical findings of the parasite?

A
  • intestinal nematode found in undercooked meats (pork/bear)
  • causes periorbital edema, fever, vomiting
  • larvae carried to striated muscle (cyst formation) and cause inflammation and myalgias
  • see inc. eosinophilic count
20
Q

Dracunuculus medinensis: how is it transmitted and how is it diagnosed?

A
  • tissue nematode transmitted by drinking copepods (larvae) in contaminated water
  • adult female Dracunuculus emerge from ulcers in patients lower extremities and must be slowly pulled out
21
Q

Onchocerca volvulus: how is it transmitted and what 3 clinical findings does it cause?

A
  • tissue nematode transmitted through black fly bites (“River Blindness”); can be seen on skin biopsy
  • causes hypo/hyperpigmentation spots w/onchodermatitis
  • microfilariae seen in eye and can cause BLINDNESS
22
Q

Wuchereria bancrofti: how is it transmitted and what 4 clinical findings does it cause? (ECWD)

A
  • tissue nematode transmitted from mosquito bites and are seen on thick blood smears
  • causes lymphatic filariasis (ELEPHANTIASIS –> chronic/severe lymphadema)
  • cause tropical pulmonary eosinophilia = nocturnal cough, wheezing, and dyspnea
23
Q

Toxocara canis: how is it transmitted and what clinical finding does it cause?

A
  • tissue nematode transmitted via food contaminated by infected DOG and cat feces
  • ocular larvae migrans can cause BLINDNESS
24
Q

Loa loa: how is it transmitted and what two clinical findings does it cause?

A
  • tissue nematode transmitted via Deer Flies and can be seen on blood smears
  • causing cyst-like collection in SubQ tissues near EYES and TENDONS, can migrate across conjunctiva (“African Eye Worm”)
25
Q

Taenia saginata and solium: how are they transmitted, what do they look like, and what clinical complication does Taenia solium cause?

A
  • cestodes (TAPEWORM)

T. saginata: found in COWS; NO hooks around mouth;

T. solium: found in PIGS; has hooks around mouth; causes Neurocysticerosis (CNS inf.); transmitted by fecal-contaminated water

  • Neurocysticerosis causes seizures and has “swiss-cheese” appearance on head CT
26
Q

Diphyllobothrium latum: how is it transmitted and what two clinical findings does it cause?

A
  • cestodes (Fish Tapeworms) from eating undercooked fish; LARGEST tapeworm (10 meters long)
  • cause B12 (cobalamin) deficiency –> megaloblastic anemia and small intestine diarrhea
  • proglottid segments seen on stool O&P
27
Q

Echinococcus granulosus: what is it and how is it transmitted, what does it look like on CT, and what is a complication of infection?

A
  • cestodes (tapeworm) transmitted via water/food contaminated with dog or sheep feces
  • cause Hydatid cysts that look like “eggshell” calcifications on liver CT
  • cyst ruptures can cause anaphylactic rxn (eosinophilia)
28
Q

Schistosoma Mansoni, Japonicum, and Haematobium: how are they transmitted, what do they look like, and what 5 clinical findings do they cause?

A
  • trematodes carried by snails that mature in the liver; can infect swimmers; migrate AGAINST portal flow

SM: eggs have LATERAL spine
SJ: small spine (round)
SH: large TERMINAL spine

  • cause “Swimmers Itch” that manifests as a rash on the legs, liver cirrhosis, portal hypertension, jaundice; hematuria
29
Q

What cancer is Shistosoma a risk factor for?

A

Squamous Cell Bladder Cancer

30
Q

Clonorchis sinensis: how is it transmitted, what 2 clinical findings does it cause, and what cancer can develop from it?

A
  • trematodes carried by snails and fish that infects the biliary tree (eggs appear operculated on stool O&P)
  • causes sclerosing cholangitis (hepatic failure), pigmented gallstones
  • inc. risk of cholangiocarcinoma
31
Q

Paragonimus westermani: what are they and how are they transmitted, and what are two clinical manifestations of infection?

A
  • trematodes carried by snails and is transmitted by raw/undercooked crab and fish meat (eggs appear operculated on stool O&P)
  • infects lungs: causes chronic cough (bloody sputum) and hemoptysis
32
Q

Prions and Transmissible Spongiform Encephalopathy

A
  • proteins that adopt alternate conformations that become SELF-PROPAGATING (NO NUCLEIC ACIDS)
  • cause cerebrocortical “spongiform” pathologic features (neuromuscular signs, cognitive defects, dementia, death)
  • long incubation period but once symptomatic, progression occurs over a period of a few months or years
33
Q

What are the 3 forms of Prions?

A
  1. Familial Form (rare): inherited Autosomal Dominant
  2. Infectious Form: eating contaminated animals
  3. Sporadic Form: unknown etiology
34
Q

Creutzfeldt-Jakob Disease

A
  • prion disease of men; NO TREATMENT
  • sporadic form is most common prion disorder in humans (85% of all cases of human PrP disease)
  • inherited form due to mutations of PrP gene (PRNP @ 20p)
  • all forms of symptomatic prion disease show RELENTLESSLY progressive neurological disease
35
Q

What 6 diseases of animals are caused by prions? (SMMFE)

A 
S - scrapie of sheep and goats
M - mink encephalopathy
M - "Mad Cow" aka bovine spongiform encephalopathy
F - feline spongiform encephalopathy
E - exotic ungulate encephalopathy
36
Q

How did “Mad Cow” disease arise?

A
  • emerged in Britian during 1980s due to industrial cannablism, where cattle were fed meat and bone meal of other cattle
37
Q

How did “Chronic Wasting Disease” arise?

A
  • prion disease endemic in deer and elk in North America
  • origin is uncertain but it is HIGHLY communicable –> feces from asymptomatic, infected wild herbivores is though to be responsible for the spread
38
Q

What is the “gold standard” for diagnosis of prions?

A
  • brain-biopsy or autopsy, with histopathologic examination and immunostaining for PrPSC in brain tissue
  • CSF unremarkable; tonsilar biopsy is HIGHLY SENSITIVE and SPECIFIC for vCJD

MOD (Mechanisms of Disease) Exam 3 (5 decks)

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