PROTOZOA (FLAGELLATES) Flashcards
Pathogenic or causing disease Flagellates
Giardia lamblia - causing Diarrhea
Trichomonas vaginalis - causing vaginitis and uriginitis
Non-pathogenic or commensal Flagellates
Trichomonas hominis
Trichomonas tenax
Chilomastix mesnii
OTHER INTESTINAL PROTOZOANS
Dientamoeba fragilis
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.
Dientamoeba fragilis
Morphology of Dientamoeba fragilis in trophozoite form
Rosette shaped nuclei (1 to 2) .
Cytoplasm may contain vacuoles with ingested debris.
Shows progressive motility.
Broad hyaline pseudopodia that possess characteristic “serrated margin.”
Mode of Transmission of Dientamoeba fragilis
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.
Pathogenesis of Dientamoeba fragilis
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)
Diagnosis and Specimen of Dientamoeba fragilis
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.
Treatment for Dientamoeba fragilis
Iodoquinol
Tetracycline and Metronidazole are also effective
Prevention and Control of Dientamoeba fragilis
Proper sanitation
Proper disposal of human waste
BASIC STRUCTURE OF FLAGELLATES
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
A pathogenic flagellates that causes diarrhea.
Giardia lamblia
Initial name of Giardia lambia and who named it.
Cercomonas intestinalis
Dr. F. Lambl
Who names the Giardia lamblia?
Stiles named from Dr. Giard and Dr. Lambl
Synonymous to Giardia duodenalis
Giardia intestinalis
Other names for Giardia lamblia
Lamblia duodenalis or L. intestinalis
Habitat of Giardia lamblia
Duodenum
Jejunum
Upper ileum of humans
Life Cycle of Giardia lamblia
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.
Morphology
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
Infective Stage
Mature cysts (resistant to routine chlorination)
Pathogenicity
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.
May lead to decrease glucose, electrolytes, fluid absorption, and deficiency in disaccharide (malabsorption and maldigestion).
Villous flattening and crypt hypertrophy
Pathology
The onset is between 1-4weeks on an average of 9 days. Half of patients are asymptomatic.
Giardia lamblia is a causative agent for
Giardiasis or Lambliasis
It is the first recorded water outbreak and involved a group of visiting travelers and where.
Gay bowel syndrome.
Failure to thrive syndrome.
“Traveler’s diarrhea” - St. Petersburg, Russia
Acute infections
“rotten eggs” odor (hydrogen sulfide)
Chronic infections
steatorrhea (malabsorption of fats) - passage of greasy, frothy stools that may float on toilet water.
Specimen
Stool and Duodenal contents
Diagnostic Stage
Trophozoite and Cyst
Lab Tests
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.
Treatment
Metronidazole: (3x a day of 1 week): drug of choice 🙣
Tinidazole, Albendazole, Furazolidone, Quinacrine and Paromomycin as alternative.
Prevention and Control
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
