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58 Cards in this Set
- Front
- Back
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Name the intestinal protozoa:
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Amoebae:
- Entamoeba histolytica - Entamoeba coli - Entamoeba dispar (non-path) - Iodamoeba (non-path) - Endolimax nana (non-path) - Blastocystis hominis Flagellates - Giardia lamblia - Chilomastix mesnili (non-path) - Dientamoeba fragilis - Trichomonas hominis Ciliates - Balantidium coli Coccidia - Cryptosporidium parvum - Cyclospora cayetanensis - Isospora belli - Sarcocystis sp. Microsporidium (intracellular) |
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Nematodes
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Ascaris
Trichuris (whipworm) Enterobius vermicularis Hookworms Strongyloides |
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Cestodes
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Taenia solium
Taenia saginata Diphyllobothrium latum ... |
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Cause of amebic dysentery, pathogenesis, & most common extra-intestinal disease
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E. histolytica
fecal-oral humans, flies, cockroaches Invasive through mucosa >90% asymptomatic LIVER ABSCESSES |
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Name & identifying characteristics
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Entamoeba histolytica
Cyst form Chromatin at edge of nucleus, beaded Trophs: - Unidirectional motility (vs E coli, multiple) - INGESTION OF RBCs -Cyst can have up to 4 nuclei (>4 rules out!) Generally: - 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 |
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Life cycle of E histolytica
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Entamoeba coli
Cyst Usually non-pathogen but can cause diarrhea >4nuc rules out E histolytica |
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Entamoeba coli
Trophozoite Very similar to E histolytica; chromatin more blotchy & clumpy; cytoplasm less smooth; larger |
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Entamoeba coli
Trophozoite MAY HAVE VACUOLES |
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Entamoeba coli
Cyst form |
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Iodamoeba butschlii
Non-pathogenic T:6-25um C: 5-15 ID: - 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) |
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Endolimax nana
Troph Smallest: 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 |
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Giardia lamblie
Flagellate 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 |
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Giardia
Trophozoite form; 9-21um Symmetrical 2 nuclei "falling leaf" motility on wet prep |
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Cryptosporidium
- protozoan - GI illness; usu kids & HIV pts - cysts remain in GI tract x 5wks - small infectious load (2-10 cysts) - resistant to chlorine |
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Organism?
Species infectious to humans? |
Cryptosporidium
C. parvum C. hominis |
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Isospora belli
Mature form (2 sporocysts) 25-30um Rare cause of diarrhea; increased in AIDS Fecal-oral transmission |
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Isospora belli, immature form (1 sporocyst)
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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 |
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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 |
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What special stain is used to ID microsporidium?
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WEBER STAIN; stains them salmon-colored
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Sarcocystis
-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) |
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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 |
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Chilomastix mesnili
-Flagellate -Warm climates; fecal-oral -Non-pathogen T: Pear shaped; **single large nuc immediately beneath outer membrane; 3 anterior flagella; pointed end |
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Chilomastix mesnili
C: pear shaped; distinctive hyaline knob off to one side; single nuc; **CURVED cytosome "shepherd's crook" which is diagnostic |
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Dientamoeba fragilis
-Flagellate -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 |
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Trichomonas hominis
-Flagellate -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 |
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Only member of the ciliates to infect humans?
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Balantidium coli
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Balantidium coli
-Fecal-oral; found in swine -Asymptomatic, self-limited infxn -Ciliates - 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 |
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NEMATODES
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NEMATODES
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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 |
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ova of ascaris
maybe fertilized (cleaved) or unfertilized. oval, thick shell. big (50-90um) |
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Diagnostic ova of trichuris thrichiura (whipworm)
-Distinct barrel shape -Refractile hyaline plugs at both ends |
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Trichuris trichiura
(Whipworm) Adults 3-5cm Male with typical coiled tail |
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Ova of enterobius vermicularis
(Pinworm) Ova have thin transparent shell, are oval and asymmetrical with one flatter side resembling an underinflated football |
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Adult female enterobius vermicularis
Characteristic pointed "pin" tail; other side has open para-oral alae |
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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 |
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Hookworm ova
OVAL Thin smooth transparent shell ** clear space beneath shell from yolk sac retraction |
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How to diagnose strongyloides? And how to tell apart from other hookworms?
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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 |
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Strongyloides stercoralis
Rhabditiform larvae (stage before filariform larvae) arrow pointing to large genital primordium (diagnostic) |
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Strongyloides stercoralis
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Hookworm, rhabditiform larvae
LONG buccal cavity |
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Strongyloides
SHORT buccal cavity |
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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 |
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CESTODES
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CESTODES
TAPEWORMS |
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Taenia saginata
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Taenia saginata tapeworm
Closeup of proglottid outlining uterine branching segments. T saginata has >14, while solium <13 |
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Taenia saginata tapeworm scolex
Does not have hooklets |
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Brain lesion
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Cysticercosis
Cysts have two walls: outer fibrous reactive tissue and inner thin membrane from worm |
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Cause of cysticercosis?
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Taenia solium
CNS involvement in 70-90% Other tapeworms as a rare cause |
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neurocysticercosis
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Taenia eggs
Cannot ID further Thick-walled spherical eggs; distinctive radial striations. Many enclose 3 pairs of hooklets |
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Diphyllobothrium latum
Fish tapeworm Tiny scolex and broad narrow proglottids Longest tapeworm that infects humans! |
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D latum proglottid
Characteristic width-over-length dimensions Nondescript central branching uterus & ovaries (ROSETTE) |
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D latum egg
Large Oval with thin smooth shell Nub at one end (arrow) **Non-shouldered operculum at other end, inconspicuous, vs the shouldered operculum of paragonimus westermani |
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Hymenolepis nana egg
Double membrane 3 pairs of hooklets inside 40-60 um Polar thickenings on either side of inner hexacanth membrane |
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Hymenolepis diminuta egg
Larger than H nana (60-80um) ABSENCE of polar thickenings 6 hooklets |
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Dipylidium caninum proglottid
Genital pore on either side is unique (other tapeworms have one lateral genital pore) |
