Term
Entamoeba histolytica
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
fecal-oral
(cyst/trophozoite stages - cyst is infective stage)
Amoeba
oocyst: infective
trophozoite: motile
-bulls eye shaped nucleus, with RBC in cytoplasm
Asymptomatic carriers (invade portal blood)
Bloody diarrhea: when trophozoites invade the intestinal mucosa, causing erosions
-amoebic dysentery (due to trophozoites secreting proteolysins)
-necrotic mucosa, abdom pain
Liver ascess
(ddx: Shigella)
*trophozoites w/ ingested RBC*
Fecal exam: cysts and trophozoites with RBC in cytoplasm (O&P - feces)
Serology (+ doesn't necessarily mean active)
Abdom CT scan - liver abscesses
90% of infected people are asymptomatic
the dehydration of the feces causes encystment
**flask-shaped ulcers** on luminal side of colon |
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Term
Giardia lamblia
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
Fecal-oral
eating beavers in CO - made me smile
Oocyst - causes spread
Flagellated trophozoite
does not invade
foul smelling, greasy diarrhea (with high fat content), and abdominal gassy distention
Flattening of mucosal surface
Fecal exam: cysts and trophozoites
Commercial immunoassay kit: test stool
looks like it has a face
pear-shaped with hairlike flagella
attach by means of sucking disks to microvilli in intestine |
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Term
Cyclospora & Isospora
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
oocyst is infective agent
Cyclospora: watery diarrhea, N&D
Isospora: severe diarrhea and malabsorption in AIDS pts
look for oocysts in stool
**acid-fast** |
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Term
Cryptosporidium parvum
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
Fecal-oral
untreated H2O
everyone sick after swimming in a lake
Sporozoan
Oocyst is infective agent
life cycle occurs within infected epithelial cells
Watery diarrhea, vomiting & abdom pain (usually self-limiting, can be life-threatening in immunocompromised pts)
Fecal exam: look for oocyst - **acid fast**
Biopsy of lining of SI
Obligate intracellular parasite
attaches to wall, no invasion |
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Term
Trichomonas vaginalis
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
STD
No cyst stage
Flagellated trophozoite, motile
Painful itching
Dysuria
Yellow-green malodorous, frothy discharge
Highly motile protozoa in vaginal discharge
Exam urine
Wet mount w/ drops of normal saline
Colonizes vagina, male urethra
Half-pear-shaped, flagella |
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Term
Balantidium coli
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
pig feces - have B. coli cysts
Ciliate protozoan
cysts and ciliated trophozoites
the largest parasitic protozoans found in the intestine
asymptomatic cyst excretion
acute colitis - N&V, abdom pain, bloody (possibly) diarrhea
chronic: intermittent episodes
ciliated trophozoites or cysts in stool |
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Term
Naegleria fowleri
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
fresh water lakes
Amoeba stage
cysts
acute meningitis, usually fatal within a week
encephalitis
CSF: look for motile amoeba, as well as WBC
CT: fronto-basal collection
brain histo: amoebic vegetations
enters nasal cavity during swimming
can see macrophage-like trophozoites |
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Term
Acanthamoeba
transmission
morphology
clinical findings
dx |
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Definition
fresh water lakes
dirty contacts
Amoeba stage
cyst stage in brain
meningoencephalitis
chronic, granulomatous brain infxn, fatal in a year
Corneal infxn: dirty contacts
exam CSF and brain tissue: both cysts and mature trophozoites
Corneal scrapings: double-walled cysts, "ring infiltrate" |
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Term
Toxoplasma gondii
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
ingestion of oocysts in raw pork
inhalation of oocysts from cat feces
congenital: pregnant women exposed
Oocyst is infectious
trophozoites
sporozoa:
oocyst releases sporozoites, penetrate
tachyzoites multiply in macropahges, get released in a burst
multiply slowly in other cells - bradyzoites
TORCH: still birth, chorioretinitis, hydrocephalus, blindness, seizures, mental retardation
Normal appearing infants may develop reactivation later on; chorioretinitis can lead to blindness
AIDS: dissemianted infxn may include encephalitis (brain mass), chorioretinitis, LN, liver, spleen enlargement, pneumonia
Serology: high IgM and IgG
CT scan shows mass in brain
Retinal exam
Obligate intracellular parasite
*intracerebral calcifications* in fetus
"crescent-shaped" tachyzoites
AIDS - get reactivation of infxn, couldn't maintain in latent state |
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Term
Pneumocystis carinii
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
acquired at an early age by respiratory route
remains latent in normal hosts
flying saucer appearing FUNGUS
Interstitial pneumonia: fever and a dry, nonproductive cough
major pathogen in AIDS pts
-15% chance of infxn/yr, 80% lifetime risk w/o prophylactics
Silver stain - see flying saucer
-saline sputum
-bronchoalveolar lavage
-bronchial wall biopsy
X-ray: interstitial pneumo with diffuse infiltrates
AIDS with CD4 < 200 susceptible
Most common opportunistic infxn in AIDS |
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Term
Plasmodium (falciparum, vivax, ovale, malariae)
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
Female anopheles mosquito = vector
injects sporozoites
Exoerythrocytic: sporozoites migrate to liver, form trophozoite -> schizont -> merozoites
RBC stages: ring form, trophozoite, schizont, gametocyte
hemolysis -> anemia, fever
Erythrocytic: merozoites -> ring trophozoites -> schizonts -> merozoites & RBC lysis
MALARIA
Periodic high fever and chills, followed by profuse sweating (sweats occur with RBC burst and release merozoites)
-Tertian malaria: every 48 hrs, P. vivax and P. ovale
-Quartan malaria: every 72 hrs, P. malariae
-P. falciparum: most common and deadly, irregular episodes
Anemia
Hepatomegaly
Splenomegaly
Brain, lung, kidney damage with P. falciparum
Exam of blood smear:
-trophozoites (ring shaped)
-schizonts
-gametocytes (sausage- or banana-shaped)
RBC that lack the cell membrane Ag Duffy a and b provides resistance to infxn by P. vivax
Sickle cell anemia trait provides resistance to infxn by P. falciparum |
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Term
Babesia microti
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
Ixodes scapularis tick
Sporozoites from tick cause infxn
mature into trophozoites in humans and infect RBC
Immunocompetent: usually asymptomatic
Immunocompromised: anemia due to hemolysis, fatigue and protracted course
Blood smear - "maltese cross"
patients may be co-infected with Lyme disease |
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Term
Leishmania
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
Sandfly bite
contaminated blood transfusion
zoonotic
Promastigote: flagellated (in sandfly)
Amastigote: intracellular & non-flagellated: in phagocytic cells of reticuloendothelial symptoms
Cutaneous leishmaniasis: single ulcer at site of bite - heals in a yr, depigmented scar
Diffuse cutaneous - nodules at bite site and over body, can last 20 yrs w/o treatment
Mucocutaneous: ulcers on mucous membranes after bite site ulcer heals; erode nasal septum/soft palate/lips, 20-40 yrs
*Visceral: Kala-azar - common in young, malnourished children. Fever, anorexia, weight loss, abdom swelling, often fatal
Demonstration of protozoa: blood smear, biopsy of lesions, spleen or liver
Leishmanin skin test is (-) in pts with low CMI
Elevated serum anti-leishmanial IgG Ab titers
Leishmania donovani: Kala-azar/visceral
L. tropica: cutaneous
Leishmania sp: mucocutaneous |
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Term
Trypanasome rhodesiense, T. gambiense
transmission
morphology
clinical findings
dx
miscellaneous |
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Definition
Tsetse fly
contaminated blood transfusion
Trypomastigote is the motile (flagellated) extracellular form living in blood, LN, and CNS
Trypomastigote and epimastigote: in tsetse fly
AFRICAN SLEEPING SICKNESS
hard, red painful skin ulcer at bite site, heals in 2 wks
fever, headache, LN swelling
fevers subside, relapses can occur
CNS symptoms: daytime drowsiness, behavioral changes, difficulty walking, slurred speech, coma, death
-T. gambiense: slowly progression, wasting, late neuro sx
-T. rhodesiense: more severe, rapid cycling, neuro sx and death in wks-mo
Visualize trypomastigotes in blood, spinal fluid, or LN
Serology (high IgM titres)
Ab agglutination test for T. gamiense
Antigenic variation: trypanosomes express on their surface a variable surface glycoprotein in a cyclic nature; as Ab form, will produce progeny with different VSG - the mechanism for the recurrent fevers |
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Term
American Trypanosome - T. cruzi
transmission
morphology
clinical findings
dx |
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Definition
Kissing bug (reduviid bug): defecates on human skin while feeding. Trypomastigotes, present in feces, tunnel into skin
Contaminated blood transfusion
Trypomastigote is the motile (flagellated) extracellular form in blood
Amastigote: intracellular and non-motile: present in macropahges, LN, and organs
Trypomastigote and epimastigote: in kissing bug
CHAGAS' DISEASE
Chagoma: hardened red area at site of parasite entry
Acute Chagas: fever, malaise, swollen LN - meningoencephalitis, acute myocarditis with tachycardia and EKG changes
Intermeidate phase: low levels of parasites and Ab, no sx, most pts remain in this phase for life
Chronic: cardiomyopathy, megadisease
Visualize trypomastigotes in blood
Xenodiagnosis: 40 lab grown bugs feed on pt... |
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