Parasites and Prions Flashcards
Giardia Lamblia: who is affected, how do they get the parasite, and what GI problems does the parasite cause?
- 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)
Entamoeba histolytica: who is affected, how do they get the parasite, and what two GI problems does this parasite cause?
- 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
Cryptosporidium: who is affected, how do they get the parasite, and what GI problems does the parasite cause?
- 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)
Toxoplasma Gondii: who is affected, how do they get the parasite, and what two CNS problems does the parasite cause in the immunocompromised?
- 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)
What are 4 symptoms of congenital Toxoplasmic infection? How would you differentiate Toxoplasma from CNS lymphoma?
- 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
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?
- 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
Naegleria fowleri: what 3 things can this parasite be found in and what is the major CNS problem it causes?
- 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
Trypanosoma cruzi (Chagas Disease): who is affected, what 3 clinical findings does the parasite cause, and what are two visual diagnostic findings?
- 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)
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?
- 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
Plasmodium malariae, ovale/vivax, and falciparum: what do they look like and what is the general fever pattern for each of the 3 groups?
- 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)
Plasmodium falciparum: what does it look like, what 3 clinical findings does it cause, and what condition can protect from it?
- 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
How is the Plasmodium parasite introduced into victims and what is its life cycle like?
- 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
Leishmania brazillensis and donovani: what does the parasite look like and what are the clinical appearances of both types?
- 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
Trichomonas vaginalis: what is it, what does it look like, and what are 4 clinical findings of the parasite?
- sexually transmitted protozoa
- motile trophozites on wet mount, pH > 4.5
- causes “strawberry” cervix w/burning, itching, and frothy yellow/green malodorous discharge
Enterobius Vermicularis (Pinworm): how are they transmitted and how can you diagnose?
- intestinal nematodes mainly affecting children through fecal-oral transmission (itching butt)
- females lay eggs at anus
- diagnosed with Scotch Tape over the anus
Ancyclostoma duodenale and Necator americanus (Hookworm): how are they transmitted, what clinical finding do they cause, and how can they be diagnosed?
- 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
Ascaris Lumbricoides (Large Roundworm): how is it transmitted, what 3 clinical findings does it cause, and how can it be diagnosed?
- 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
Strongyloides stercoralis: how is it transmitted and how can it be diagnosed?
- 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
Trichinella spiralis: what is the parasite found in and what are 5 clinical findings of the parasite?
- 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
Dracunuculus medinensis: how is it transmitted and how is it diagnosed?
- 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
Onchocerca volvulus: how is it transmitted and what 3 clinical findings does it cause?
- 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
Wuchereria bancrofti: how is it transmitted and what 4 clinical findings does it cause? (ECWD)
- 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
Toxocara canis: how is it transmitted and what clinical finding does it cause?
- tissue nematode transmitted via food contaminated by infected DOG and cat feces
- ocular larvae migrans can cause BLINDNESS
Loa loa: how is it transmitted and what two clinical findings does it cause?
- 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”)
Taenia saginata and solium: how are they transmitted, what do they look like, and what clinical complication does Taenia solium cause?
- 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
Diphyllobothrium latum: how is it transmitted and what two clinical findings does it cause?
- 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
Echinococcus granulosus: what is it and how is it transmitted, what does it look like on CT, and what is a complication of infection?
- 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)
Schistosoma Mansoni, Japonicum, and Haematobium: how are they transmitted, what do they look like, and what 5 clinical findings do they cause?
- 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
What cancer is Shistosoma a risk factor for?
Squamous Cell Bladder Cancer
Clonorchis sinensis: how is it transmitted, what 2 clinical findings does it cause, and what cancer can develop from it?
- 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
Paragonimus westermani: what are they and how are they transmitted, and what are two clinical manifestations of infection?
- 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
Prions and Transmissible Spongiform Encephalopathy
- 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
What are the 3 forms of Prions?
- Familial Form (rare): inherited Autosomal Dominant
- Infectious Form: eating contaminated animals
- Sporadic Form: unknown etiology
Creutzfeldt-Jakob Disease
- 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
What 6 diseases of animals are caused by prions? (SMMFE)
S - scrapie of sheep and goats M - mink encephalopathy M - "Mad Cow" aka bovine spongiform encephalopathy F - feline spongiform encephalopathy E - exotic ungulate encephalopathy
How did “Mad Cow” disease arise?
- emerged in Britian during 1980s due to industrial cannablism, where cattle were fed meat and bone meal of other cattle
How did “Chronic Wasting Disease” arise?
- 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
What is the “gold standard” for diagnosis of prions?
- 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
