Protozoans

• What are the three kingdoms under which unicellular parasites are classified?

  Protozoa, Stramenopila, Fungi
• What is the size range of protozoa?

  1. 100 µm
• What encloses the protoplasm of protozoa?

  A cell membrane
• What does the nucleus of protozoa contain?

  Clumped or dispersed chromatin and a karyosome
• What are the organelles of locomotion in protozoa?

  Pseudopods, flagella, or cilia
• How many major subgroups or phyla does the kingdom Protozoa comprise?

  13 major subgroups or phyla
• Which seven phyla of protozoa are of concern in medical parasitology?

  Metamonada, Parabasia, Percoloza, Euglenozoa, Amoebozoa, Sporozoa, Ciliphora
• How are protozoa classified based on locomotion?

  • Sarcodina (Amoebae) use pseudopodia
  • Ciliophora (Ciliates) use cilia
  • Mastigophora (Flagellates) use flagella
  • Apicomplexa (Sporozoa) possess microtubule complex
• What are the single-celled organisms belonging to the subkingdom or phylum Amoebozoa called?

  Amoebae
• To which class do intestinal parasites of amoebae belong?

  Entamoebidae
• Which genera of amoebae parasitize the intestinal tracts of humans?

  Entamoeba, Endolimax, Iodamoeba
• What are the two components of the cytoplasm in amoebae?

  Endoplasm and ectoplasm
• How do amoebae reproduce?

  By binary fission
• What is the life cycle of amoebae like?

  • Shapeless mass of moving cytoplasm
  • Divided into granular endoplasm and clear ectoplasm
  • Movement via pseudopodia
  • Feeding through phagocytosis
  • Infectious form is the cyst
• What is the infectious form of amoebae acquired by ingestion of contaminated material?

  The cyst
• What happens once the cyst reaches the intestinal tract?

  Excystation occurs, releasing trophozoites
• Where does encystment occur in amoebae?

  In the colon
• How long can cysts remain viable in the environment?

  Days to weeks
• What is the most widespread pathogenic disease caused by amoebae?

  Amoebiasis or amoebic dysentery
• How is amoebiasis transmitted?

  Through fecally contaminated food, water, or materials
• What is the causative agent of amoebiasis?

  Entamoeba histolytica
• What distinguishes E. histolytica from E. dispar and E. moshkovskii in stool tests?

  They cannot be distinguished by a stool ova and parasite (O&P) test
• What is the size range of trophozoites of E. histolytica?

  12–60 μm
• How do trophozoites of E. histolytica move?

  Exhibit progressive rapid and directional movement
• What is the diagnostic feature of E. histolytica infection?

  Presence of RBCs in the cytoplasm of trophozoites
• What happens to the cysts when conditions become unfavorable for trophozoites?

  Cysts develop
• Where is E. histolytica more prevalent?

  In tropical and subtropical regions
• How does infection occur with E. histolytica?

  By ingestion of cysts from contaminated material
• What has epidemiologic evidence shown about E. histolytica transmission?

  Significant sexual transmission among men who have sex with men
• What leads to fecal exposure in sexual transmission of E. histolytica?

  Direct oral-anal contact
• What are the stages of infection by Entamoeba histolytica?

  1. Cysts passed in feces
  2. Ingestion of mature cysts
  3. Excystation in the small intestine
  4. Release of trophozoites
  5. Migration to the large intestine
  6. Multiplication by binary fission
  7. Cysts and trophozoites passed in feces
• What happens to trophozoites once passed in stool?

  They are rapidly destroyed outside the body
• What is the difference between invasive and noninvasive infections of E. histolytica?

  Invasive infections involve trophozoites invading intestinal mucosa
• What is the diagnostic feature of E. histolytica infection?

  Ingested red blood cells in trophozoites
• What is the first stage in the invasive pathogenesis of E. histolytica?

  Attachment of the trophozoite to human target cells
• What do amoebae produce to aid in their spread in the submucosa?

  Neutral cysteine proteinases
• What is the result of E. histolytica engulfing fragments of human cells?

  Death of the cell due to loss of membrane integrity
• What percentage of E. histolytica infections are asymptomatic?

  The majority
• What are the symptoms of amoebic dysentery?

  Diarrhea, cramping, lower abdominal pain, low-grade fever, blood and mucus in stool
• What is an amoeboma?

  A large inflammatory mass in the gastrointestinal tract