Dientameoeba fragilis

Question 1

How is D. fragilis classified?

Answer 1

Extracellular anaerobic intestinal protozoa belonging to the flagellates

Question 2

What is the life cycle of D. fragilis?

Answer 2

1. Trophozoites of D. fragilis is found in the feces of infected humans since it has no confirmed cyst stage
2. Transmission probably occurs through the fecal-oral route (by helminths eggs)
3. Transmission might also occur in combination with helminths eggs, primarily Enterobius vermicularis but also Ascaris and others
4. After transmission occurs D. fragilis trophozoites colonize in the lumen of the large intestine in mucosal crypts. Asexual reproduction occurs through binary fission and the trophozoites leave the body in the feces

Question 3

What type of life cycle does D. fragilis have?

Answer 3

Direct life cycle

Question 4

What are other reserviors of D. fragilis?

Answer 4

other mammals (non-human primates) - however epidemiological significance remains unknown

Question 5

What is the incubation time of D. fragilis?

Answer 5

Unknown

Question 6

What are the symptoms caused by D. fragilis?

Answer 6

Asymptomatic

Symptomatic

• gastrointestinal upset
• parasite does not penetrate the tissue so symptoms caused may be due to irritation which stimulates colonic motility

Question 7

Where is D. fragilis endemic?

Answer 7

• Worldwide, however more common in developed countries (crowded spaces, traveling to unconventional countries)
• More common in children

Question 8

How is D. fragilis diagnosed?

Answer 8

Microscopy

• examination of trophozoites in stained fecal smears
• trophozoites are easily overlooked or misidentified because they are pale-staining and their nuclei sometimes resemble those of Endolimax nana or Entamoeba hartmanni

PCR
- should be approached with caution because of the performance variability across platforms and the potential low specificity