Entamoeba Histolytica Infection

Intestinal Amoeba

• Entamoeba histolytica: has 8 nucleus in mature cyst, ingested RBCs are found in trophozoites, and asymptomatic individuals with documented infection should be treated.
• Entamoeba coli: has 4 nucleus in mature cyst.
• Endolimax nana: a type of intestinal amoeba.
• Iodamoeba butschlii: a type of intestinal amoeba.
• Blastocystis hominis: a type of intestinal amoeba.

Free Living Amoeba

• Naegleria fowleri: has 3 morphological forms (amboebae, flagellates, and cysts).
• Acanthamoeba spp.: causes diseases such as keratitis and encephalitis.

Intestinal and Atrial Flagellates and Ciliates

• Giardia lamblia:
  • Oval and lightly bile-stained, with a diameter of 8-12 mm.
  • Has 4 nucleus in mature cyst, with a small eccentric karyosome.
  • Clear space beneath the thin cyst wall.
  • Infection occurs through ingestion of cysts in contaminated water, food, or via the fecal-oral route.
  • Excystation releases trophozoites in the small intestine, which multiply by longitudinal binary fission.
  • Encystation occurs as the parasites transit towards the colon.
  • Cysts are infectious when passed in the stool or shortly afterward, making person-to-person transmission possible.
  • Treatment options include quinacrine, metronidazole, and furazolidone for children.
  • Prevention involves avoiding contaminated food and water, proper disposal of feces, good personal hygiene, and proper storage of food and water.
• Trichomonas vaginalis:
  • Genital flagellate, found in the vagina and urethra.
  • Has 3-5 anterior flagella and one undulating membrane.
  • Distribution is worldwide, and transmission occurs through sexual contact, contaminated towels, and contaminated examination equipment.
  • Infection causes trichomoniasis, which is usually asymptomatic in males but can cause urethritis with a thin, white urethral discharge.
  • In females, infection causes vaginitis with an offensive yellowish discharge, and grows optimally at pH 5.5-6.0.
  • Diagnosis involves microscopic examination, detection of motile trophozoites in a wet preparation of vaginal or urethral discharge.
  • Treatment options are not specified.
• Dientamoeba fragilis:
  • Has a pear-shaped trophozoite with a length of 10-30 mm and a width of 5-20 mm.
  • Has an ovoid nucleus at the anterior, 4 anterior flagella, and an undulating membrane from the anterior to the middle of the body.
  • Axostyle runs from the anterior to the posterior and ends like a tail.
  • Infection occurs through contaminated food and water, and causes diarrhea.
  • Diagnosis involves microscopic examination, and treatment options are not specified.
• Balantidium coli:
  • Only ciliate protozoan parasite of humans, and the largest protozoan.
  • Distribution is worldwide, and natural hosts are pigs, with accidental hosts being humans.
  • Reservoirs include monkeys, pigs, and rats.
  • Site of infection is the large intestine.
  • Trophozoite has a large kidney-shaped macronucleus and a small micronucleus.
  • Cyst has a thick and transparent double-layered wall.
  • Pathogenesis involves mucosal ulcers and submucosal abscesses.
  • Diagnosis involves stool examination, biopsy, and cultures.
  • Treatment options include tetracycline, metronidazole, and nitroimidazote.

Life Cycle of Protozoa

• Giardia lamblia: excystation releases trophozoites, which multiply by longitudinal binary fission, and encystation occurs as the parasites transit towards the colon.
• Trichomonas vaginalis: transmitted by sexual contact, and multiplies by longitudinal binary fission.
• Dientamoeba fragilis: no life cycle mentioned.
• Balantidium coli: trophozoite multiplies by transverse binary fission, and conjugation occurs.

Blood and Tissue Flagellates

• Leishmania spp.: causes diseases such as kala-azar, cutaneous leishmaniasis, and mucocutaneous leishmaniasis.
• Trypanosoma spp.: causes diseases such as African trypanosomiasis and Chagas disease.

Blood and Tissue Sporozoa

• Plasmodium vivax: causes vivax malaria.
• Plasmodium ovale: causes ovale malaria.
• Plasmodium malariae: causes malariae malaria.