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58 Cards in this Set

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Name the intestinal protozoa:
- Entamoeba histolytica
- Entamoeba coli
- Entamoeba dispar (non-path)
- Iodamoeba (non-path)
- Endolimax nana (non-path)
- Blastocystis hominis

- Giardia lamblia
- Chilomastix mesnili (non-path)
- Dientamoeba fragilis
- Trichomonas hominis

- Balantidium coli

- Cryptosporidium parvum
- Cyclospora cayetanensis
- Isospora belli
- Sarcocystis sp.

Microsporidium (intracellular)
Trichuris (whipworm)
Enterobius vermicularis
Taenia solium
Taenia saginata
Diphyllobothrium latum
Cause of amebic dysentery, pathogenesis, & most common extra-intestinal disease
E. histolytica

fecal-oral humans, flies, cockroaches
Invasive through mucosa

>90% asymptomatic

Name & identifying characteristics
Entamoeba histolytica
Cyst form
Chromatin at edge of nucleus, beaded

- Unidirectional motility (vs E coli, multiple)
-Cyst can have up to 4 nuclei (>4 rules out!)

- E hist is smaller (T 12-40um, C10-20) vs E coli (T15-50, C10-35)
- Intranuclear karyosomes more central in E hist
- Rim of nuclear chromatin is beadlike in E hist, vs blotchy
Life cycle of E histolytica
Entamoeba coli

Usually non-pathogen but can cause diarrhea

>4nuc rules out E histolytica
Entamoeba coli

Very similar to E histolytica; chromatin more blotchy & clumpy; cytoplasm less smooth; larger
Entamoeba coli

Entamoeba coli
Cyst form
Iodamoeba butschlii

C: 5-15

- ball-in-socket nucleus (~E nana)
- Cyst contains large iodine staining glycogen vacuole (E coli & E hist can also have vacuoles in early stage, but usu >1nuc)
Endolimax nana

T 5-8um; C 5-24um
Can be difficult to distinguish from Iodamoeba

No peripheral chromatin; Has ball-in-socket nucleus; up to 4 nuclei per cyst
Giardia lamblie
Cyst form

Cysts: 8-12um
- oval
- 4 nuclei (mature form)
- Eccentric karyosome
- no peripheral chromatin on nuc membrane
- clear space beneath cyst wall = HALO EFFECT
- ill-defined longitudinal fibrils
Trophozoite form; 9-21um
2 nuclei
"falling leaf" motility on wet prep

- protozoan
- GI illness; usu kids & HIV pts
- cysts remain in GI tract x 5wks
- small infectious load (2-10 cysts)
- resistant to chlorine

Species infectious to humans?

C. parvum
C. hominis
Isospora belli

Mature form (2 sporocysts)

Rare cause of diarrhea; increased in AIDS
Fecal-oral transmission
Isospora belli, immature form (1 sporocyst)
Cyclospora cayetanensis

- 2x size of cryptosporidium; ill-defined internal structure
- Not detected with normal fecal stains; must use acid-fast, saffranin, or auto-fluorescence
- Causes traveler's diarrhea
- Sporulation takes several weeks so person-person transmission does not occur
Microsporidium species

-Very small! 1-3um
- 700 species
-Infect insects, fish, crustaceans, some human
-Dx: H&E, silver, PAS of intestincal epithelium; EM is gold standard; fecal smear will show tiny spores, characteristically with transverse septum
What special stain is used to ID microsporidium?
WEBER STAIN; stains them salmon-colored

-Ingestion poorly cooked pork/beef or ingestion of cysts from animal stool
-Can develop in skeletal muscle or in GI (fecal smears with 10-20um oval oocysts)
Blastocystis hominis

-Questionable pathogen
- irregularly sized spherical cells 5-15um
- Homogeneous staining central body occupies >70% of the cell
- Nuclear material scattered around central body OR in 2 elongated masses
Chilomastix mesnili

-Warm climates; fecal-oral
T: Pear shaped; **single large nuc immediately beneath outer membrane; 3 anterior flagella; pointed end
Chilomastix mesnili

C: pear shaped; distinctive hyaline knob off to one side; single nuc; **CURVED cytosome "shepherd's crook" which is diagnostic
Dientamoeba fragilis

-D, abd pain, wt loss
-No known cyst form
-T: asymmetrical; 2 nuclei; prominent karyosomes

-**Higher incidence in kids with pinworm
-Thx with tetracycine, metro
Trichomonas hominis

-not pathogenic; don't stain well; no cyst form
-Teardrop shape with single anterior nucleus (though not against the membrane like chilomastix)
-Undulating membrane extends entire cell, vs T vag extends half
-Stiff rotary motility
-DDx: T vaginalis in females, contaminant
Only member of the ciliates to infect humans?
Balantidium coli
Balantidium coli

-Fecal-oral; found in swine
-Asymptomatic, self-limited infxn
- Easy to recognize in stool: LARGE (100um)
-T: Short cilia cover outer membrane; large kidney shaped nuc with small micro-nuc adjacent; rotary motility
-C: Spherical to elliptical, 50-65um; single macro nuc with a hof containing a micronuc; small vacuoles
Ascaris lumbricoides

very large; 15-35 cm

fecal-oral: eggs- larvae in GI- circulation- lungs- trachea- swallow- become adults in GI- lay eggs in feces
ova of ascaris

maybe fertilized (cleaved) or unfertilized. oval, thick shell. big (50-90um)
Diagnostic ova of trichuris thrichiura (whipworm)

-Distinct barrel shape
-Refractile hyaline plugs at both ends
Trichuris trichiura

Adults 3-5cm
Male with typical coiled tail
Ova of enterobius vermicularis

Ova have thin transparent shell, are oval and asymmetrical with one flatter side resembling an underinflated football
Adult female enterobius vermicularis

Characteristic pointed "pin" tail; other side has open para-oral alae
Old World hookworm

New World hookworm
Ancylostoma duodenale

Necator americanus

Same life cycle; same ova appearance
Circulation --> lungs --> swallow --> attach to small intestine Cause anemia
Hookworm ova

Thin smooth transparent shell
** clear space beneath shell from yolk sac retraction
How to diagnose strongyloides? And how to tell apart from other hookworms?
Observing motile rhabditiform larvae rather than ova in stool specimens, because they hatch in the intestine

SS larvae have short buccal cavity (vs long in other hookworms) and a prominent genital primordium 1/3 from the tail
Strongyloides stercoralis

Rhabditiform larvae (stage before filariform larvae)
arrow pointing to large genital primordium (diagnostic)
Strongyloides stercoralis
Hookworm, rhabditiform larvae

LONG buccal cavity

SHORT buccal cavity
Capillaria philippinensis

Fish-bird life cycle
Always pathogenic; High IgE

Ova very similar to Trichuris trichiura except have BROAD FLAT protuberances and a STRIATED SHELL
Taenia saginata
Taenia saginata tapeworm

Closeup of proglottid outlining uterine branching segments. T saginata has >14, while solium <13
Taenia saginata tapeworm scolex

Does not have hooklets
Brain lesion

Cysts have two walls: outer fibrous reactive tissue and inner thin membrane from worm
Cause of cysticercosis?
Taenia solium

CNS involvement in 70-90%
Other tapeworms as a rare cause
Taenia eggs

Cannot ID further

Thick-walled spherical eggs; distinctive radial striations.

Many enclose 3 pairs of hooklets
Diphyllobothrium latum

Fish tapeworm

Tiny scolex and broad narrow proglottids

Longest tapeworm that infects humans!
D latum proglottid

Characteristic width-over-length dimensions
Nondescript central branching uterus & ovaries (ROSETTE)
D latum egg

Oval with thin smooth shell
Nub at one end (arrow)
**Non-shouldered operculum at other end, inconspicuous, vs the shouldered operculum of paragonimus westermani
Hymenolepis nana egg

Double membrane
3 pairs of hooklets inside
40-60 um
Polar thickenings on either side of inner hexacanth membrane
Hymenolepis diminuta egg

Larger than H nana (60-80um)
ABSENCE of polar thickenings
6 hooklets
Dipylidium caninum proglottid

Genital pore on either side is unique (other tapeworms have one lateral genital pore)