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Parasitology > PROTOZOA (FLAGELLATES) > Flashcards

PROTOZOA (FLAGELLATES) Flashcards

1
Q

Pathogenic or causing disease Flagellates

A

Giardia lamblia - causing Diarrhea

Trichomonas vaginalis - causing vaginitis and uriginitis

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2
Q

Non-pathogenic or commensal Flagellates

A

Trichomonas hominis
Trichomonas tenax
Chilomastix mesnii

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3
Q

OTHER INTESTINAL PROTOZOANS

A

Dientamoeba fragilis

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4
Q

Despite of its name, it is not an amoeba but an intestinal flagellate.

No cyst stage identified, only the trophozoite stage is known.

Originally described as an amoeba (based on EM and immunologic
and molecular phylogenic findings it is actually a flagellate)

Resembles Trichomonas.

A

Dientamoeba fragilis

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5
Q

Morphology of Dientamoeba fragilis in trophozoite form

A

Rosette shaped nuclei (1 to 2) .

Cytoplasm may contain vacuoles with ingested debris.

Shows progressive motility.

Broad hyaline pseudopodia that possess characteristic “serrated margin.”

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6
Q

Mode of Transmission of Dientamoeba fragilis

A

Fecal-oral route via transmission of helminth eggs (eg., Enterobius vermicularis)

It has been observed that some of Dientamoeba fragilis are found in the lumen of the Enterobius vermicularis adult.

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7
Q

Pathogenesis of Dientamoeba fragilis

A

Infections are asymptomatic because it does not invade the tissues compare to E. histolytica. The presence of this parasite in GIT only produces irritation of the mucosa with secretion of excess mucus and hypermotility of the bowel.

In chronic infections, it may only mimic the irritable bowel syndromes but primarily the infection is asymptomatic because the parasite is not invading the tissues.

Possible co-infection with E. vermicularis and A. lumbricoides 🙣 Chronic infections may mimic Irritable Bowel Syndrome (IBS)

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8
Q

Diagnosis and Specimen of Dientamoeba fragilis

A

Observation of binucleate trophozoites in multiple fixed and stained fresh stool

Microscopy and direct fecal smear.

Purged stool- provides more suitable material for examination than the average formed stool. We use laxatives in purged stool. Suitable specimen for detecting Dientamoeba fragilis.

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9
Q

Treatment for Dientamoeba fragilis

A

Iodoquinol

Tetracycline and Metronidazole are also effective

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10
Q

Prevention and Control of Dientamoeba fragilis

A

Proper sanitation

Proper disposal of human waste

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11
Q

BASIC STRUCTURE OF FLAGELLATES

A

Flagellum/Flagella- locomotor apparatus.

Kinetoplast- provides energy

Blepharoplast

Parabasal body

Cytostome- cell mouth

Undulating membrane- a membrane laterally projecting from the body of certain flagellates, participate in active motility of the flagella.

Axostyle or axial rod- for support in locomotion

Costa- rib-like structure within the cytostome for support

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12
Q

A pathogenic flagellates that causes diarrhea.

A

Giardia lamblia

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13
Q

Initial name of Giardia lambia and who named it.

A

Cercomonas intestinalis

Dr. F. Lambl

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14
Q

Who names the Giardia lamblia?

A

Stiles named from Dr. Giard and Dr. Lambl

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15
Q

Synonymous to Giardia duodenalis

A

Giardia intestinalis

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16
Q

Other names for Giardia lamblia

A

Lamblia duodenalis or L. intestinalis

17
Q

Habitat of Giardia lamblia

A

Duodenum

Jejunum

Upper ileum of humans

18
Q

Life Cycle of Giardia lamblia

A

Ingested mature cyst will pass safely through the stomach; it will undergo excystation in the duodenum for about 30 mins, developing into trophozoites that rapidly multiply (binary fission) and attach to intestinal villi causing pathologic changes.

As the feces dehydrates, the parasite will undergo encystation.

The mature cyst will pass through the feces (infectious).

Trophozoites may be isolated on the fecal sample.

Diagnostic stage are cyst and trophozoites.

19
Q

Morphology

A

Trophozoite Form:

  • “Old-man with eyeglasses”, “Monkey Face”
  • Pear/tear drop shaped, pyriform, shape of a tennis racket.
  • Bilaterally symmetrical with large ventral sucking disc pathogenic determinant.
  • Ventral sucking disc- attachment to intestinal villi.
  • 4 pairs of flagella, 2 ventral sucking disc.
  • 2 ovoidal nuclei with distinct karyosome (symmetrically bilateral).
  • “falling leaf motility”- movement.
  • Covered with variant-specific surface proteins (VSPs) - function is not fully elucidated but it is used as resistance for intestinal proteases attributing to the survival of the parasite.

Cyst Form

*Ovoidal in shape
* Thick shell (double wall), surrounded by a hyaline cyst wall
* Nuclei: 2 (young), 4 (mature)
* Presence of axostyle

20
Q

Infective Stage

A

Mature cysts (resistant to routine chlorination)

21
Q

Pathogenicity

A

Parasite attach to intestinal walls via adhesive sucking disc located on the ventral side, it causes mechanical irritation in the affected tissue.

It produces lectin for attachments.

The parasite is able to avoid peristalsis by trapping itself between the villi or within the intestinal mucosa.

22
Q

May lead to decrease glucose, electrolytes, fluid absorption, and deficiency in disaccharide (malabsorption and maldigestion).

A

Villous flattening and crypt hypertrophy

23
Q

Pathology

A

The onset is between 1-4weeks on an average of 9 days. Half of patients are asymptomatic.

24
Q

Giardia lamblia is a causative agent for

A

Giardiasis or Lambliasis

25
Q

It is the first recorded water outbreak and involved a group of visiting travelers and where.

Gay bowel syndrome.

Failure to thrive syndrome.

A

“Traveler’s diarrhea” - St. Petersburg, Russia

26
Q

Acute infections

A

“rotten eggs” odor (hydrogen sulfide)

27
Q

Chronic infections

A

steatorrhea (malabsorption of fats) - passage of greasy, frothy stools that may float on toilet water.

28
Q

Specimen

A

Stool and Duodenal contents

29
Q

Diagnostic Stage

A

Trophozoite and Cyst

30
Q

Lab Tests

A

Direct Fecal Smear

Entero test/Enterotube test/string test/ Beale

String’s test (non-invasive)

Aspirate and Biopsy (invasive)

Concentration techniques in low level of light infections

Antigen detection test and immunofluorescence commercial test kit- Cyst wall protein 1 (Giardia antigen found in the stool)

Direct fluorescent antibody testing- Gold standard because it provides high sensitivity and high specificity.

31
Q

Treatment

A

Metronidazole: (3x a day of 1 week): drug of choice 🙣

Tinidazole, Albendazole, Furazolidone, Quinacrine and Paromomycin as alternative.

32
Q

Prevention and Control

A

Proper disposal of human excreta

Improve access to clean and safe drinking water - (Proper water treatment that includes combination of chemical therapy and filtration)

Good food preparation practices

Avoid using “night soil´

Health education and promotion

33
Q
A

Parasitology (5 decks)

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