Parasitology Organisms

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Which group of protozoans do Entamoeba histolytica and coli belong to?


How do Entamoeba histolytica and coli move and reproduce?

Move: Extension of pseudopodia (false feet)
Reproduce: Asexually by binary fission

________ represent the active feeding form and also the stage that infects human tissue.


_______ represent the inactive, resting form but also the infective form as they are able to survive _____ acids on route to the _______

Cysts, gastric, intestine

Entamoeba histolytica and coli are the most/least common amoeba found in stool examination?


Why is differentiating the species so important?

E. coli is a harmless commensal and not unusual to find in people living in areas of poor sanitation

Entamoeba histolytica is the cause of?

Amoebic dysentry

Describe Entamoeba histolytica trophozoites
Size, move, food particles, nucleus

Size: Average 15-20 um
Move: Pseudopodia
Food particles: RBC
Nucleus: Central karysome, nuclear membrane with fine chromatin ring

Describe Entamoeba histolytica cysts
Size, nuclei, chromatoidal bars

Size: 10-20 um
Nuclei: 4 max
Chromatodial bars: 1-2 with rounded ends (cigar shaped)

Describe Entamoeba coli trophozoites
Size, move, food particles, nucleus

Size: 10-20 um or slightly larger
Move: Non-directional with blunt pseudopodia
Food particles: No RBC (bacteria, yeast, garbage)
Nucleus: eccentric karyosome, irregular chromatin

Describe Entamoeba coli cysts
Size, nuclei, chromatoidal bars

Size: 10-35 um
Nuclei: Eight max
Chromatodial bars: 0-2 with frayed ends

Giardi lamblia belong to which group of protozoans?


How do flagellates move?

By whip-like flagella

How is "beaver fever" infection spread?

Cysts have 4 nuclei and when the cyst wall is removed by digestive jucies, two binucleate trophozoites emerge. They attach to epithelial cells in the crypts of duodenum and upper jejunum by ventral sucking discs

What are the symptoms of Giardi lamblia?

Severe diarrhea with foul, mucus filled stool
Pain, nausea, anorexia

Who may be at rish of chronic infections with Giardi lamblia?

Those with IgA deficiencies

What is the best treatment for Giardia lamblia?


Describe Giardia lamblia
Wet prep, Stained prep, size, flagella, nuclei, sucking disc, media bodies

Wet Prep: Falling leaf motility
Stain Prep: Reveals diagnostic features
Size: Pear shaped, 10-20um x 5-15um
Flagella: 4 pair
Nuclei: 2
Sucking disc: large disc on ventral surface
Median bodies: two sausage shaped bodies below disc

Describe Giardi lamblia cysts unstained

Football shaped
4 nuclei clustered at one end

Describe Giardi lamblia cysts stained

Thin walled with granular contents
Size:8-12 um x 7-10 um
Nuclei: 4 at one end
Longitudinal fibrils may be seen along with four dark staining median bodies

What is available for direct detection of Giardia antigen from stool samples?

Direct immunofluorescent (DFA)
Enzyme Immunassay (EIA)

What does DFA detect?

Giardia and/or Cryptosporidium

What does EIA detect?

Giarida specific proteins and antigen

What protozoan group does Trichomonas vaginalas belong to?


What tract does Trichomonas vaginalas infect?


Describe female infection of Trichomonas vaginalas

Trophozoites colonize surface epithelial cells in vagina and urethra

Vaginal itching, burning, dysuria, thic discharge

Describe male infection of Trichomonas vaginalas

Asymptomatic but an occassional scant discharge

Describe morphology of Trichomonas vaginalas

12-26 um (large wbc)
4 anterior flagella
1 nucleus
Undulating membrane along one side

Which specimens can be used to diagnose Trichomonas vaginals?

Vaginal or urethral sections
Prostatic sections
Urine sediment

What are 3 methods for Trichomonas vaginalas diagnosis?

Culture, Immunological Diagnosis, Dipstick

Describe the Trichomonas dipstick method

Swab is added to lysis reagent
Dipstick is added and incubated
Reaction is read as positve or negative

Which group does Cryptosporidium belong to?


How do Coccidia differ from other protozoans?

Have both sexual (gametogony) and asexual (shizogony) stage in life cycle

What is the infective form of Cryptosporidium?


oocyst contants ____ sporozoites


Cryptosporidium oocyst pathogenicity

Some people may be asymptomatic while others have a mild self-limitung infections

Cryptosporidium is diagnosed by?

Finding oocytes in the stool or identifying antigen with immunological methods

What is the most common worm infection in humans?

Enterobius vermicularis

How long does it take for enterobius to reach sexual maturity?

2-6 weeks

How does the reinfection cycle usually occur with enterobius vermicularis?

Eggs on perianal area cause itching which leads to contamination on hands

How long are Enterobius vermicularis eggs viable for?

10 days

Describe pin worm ova

50 x 25 um
Flattened on one side
Embryo may be seen
Wall of ova has purplish tinge

What is Trichuris trichuria commonly know as?

Whip worm

What does a severe infection of Trichuris trichuria lead to?

Bloody diarrhea, rectal prolapse
Eosinophilia and urticaria (hives)

Describe the ova of Trichuris trichuria

50 x 20um
Polar plugs
Barrel shaped
Thick walled, bile stained

What is the largest nematode to infect man?

Ascaris lumbercoides

What may be present in a person suffering from Ascaris lumbricoides?

Larvae, blood in sputum
Urticaria, eosinophilia

Describe the ova of Ascaris lumbricoides

65 x 45 um
thick walled, bile stained
Warty, albuminous coat

Describe scolex

anterior attachment "organ"

Describe proglottids

Segments making up the tape worm

Describe food system of tape worms

Food is absorbed

Describe life cycle of tape worm

requires more than 1 host

Source of Taneia solium


Source of Taenia saginata


Source of Diphyllobothrium


Scolex of Taenia solium

1-4 mm
Hook and 4 suckers

Scolex of Taenia saginata

1-4 mm
4 suckers

Scolex of Diphyllobothrium

1-4 mm
Almond shaped
2 bothria

Proglottids of Taenia solium

5-13 coarse
Uterine branches

Proglottids of Taenia saginata

15-30 fine uterine branches

Proglottids of Diphyllobothrium

Rosette shaped uterus

Ova of Taenia solium

35 um
Thick, striated wall

Ova of Taenia saginata

35 um
Thick striated wall

Ova of Diphyllobothrium

70-45 um
Thin walled lid

Unique characteristics of Dientamoeba fragilis

Fragmented nuclei composed of 4-8 granules
No cyst stage exists

Describe Charcot Leyden Crystals

Breakdown products of eosinophils
Tissue-invading parasite infections or active allergic reactions
Double sided pyramid

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