Amebiasis | Anatomy2Medicine
Amebiasis Symptoms

Amebiasis

 

  • Entamoeba histolytica
  • Trophozoites
      • In cases where amoebic dysentery is suspected, a fresh fecal sample is necessary.
      • A fresh stool while still warm should be examined quickly in order to see the colorless and motile trophozoites
      • The motile form of the trophozoite has one nucleus
      • Lugol’s iodine is frequently used and the stain kills the parasite almost immediately
  • E. histolytica vs Entamoeba. coli. (MCQ)
        • Stained Entamoeba histolytica trophozoites have a transparent outer border (ectoplasm) and an opaque inner border (endoplasm).
        • The border between endoplasm and ectoplasm is not distinct in Entamoeba .coli
      • trophozoite of E. histolytica contain red blood cells (unlike other amoebae).
        • pathognomonic (diagnostic) for pathogenic Entamoeba histolytica (MCQ)
        • but is not always present.
  • Chromatoid bodies. (MCQ)
        • Ribosomes can be arranged in characteristically shaped elongate bars with rounded ends
    • Cysts
      • cysts of  E. histolytica posses four nuclei. (MCQ)
      • cysts of Entamoeba coli  have eight nuclei (MCQ)
    • Symptoms
      • abdominal pain
      • diarrhea with blood in the stool specimen,
      • moderately febrile
      • tenesmus, – If the rectum is affected
      • Perianal ulcers
  • Symptoms may mimic ulcerative colitis and diverticulitis(MCQ)
    • Fulminant colitis due to amoebal infection
      • severe and sudden onset.
      • characterized by high fever and intestinal bleeding
      • can cause perforation of the colon.
    • Amoeboma with a mass may occur
      • misdiagnosed as colon cancer.
  • Life Cycle
    • The mature cysts are ingested and passed into the small intestine where excystation (“hatching”) takes place.
    • The “freed” cyst then develops into a trophozoite form
    • trophozoite proceeds to multiply through binary fission in the lumen
    • Trophozoites may then initiate a process called encystations, and immature cysts are excreted
    • fecal contamination begins the infective cycle that would impact other animals.
    • Both immature and mature cysts are found in the feces along with trophozoites, a stage that is most prevalent in watery stools.
    • Some trophozoites may invade the colon’s wall where they multiply and pass into the vascular system to infect organs outside the colon
  • Disease Transmission
    • Sources of most cases of amebiasis.
      • Food and water contaminated with amoebic cyst
      • sexual intercourse involving anal penetration (MCQ)
    • When E. histolytica trophozoites pass through the colon walls and enter the circulatory system, they lead to  abscesses in liver and the brain or lungs.
  • Laboratory Diagnosis
    • Charcot-Leyden crystals for disintegrated eosinophils may provide clues that parasites may be present. (MCQ)
    • In active dysentery, no cysts of E. histolytica are found in the feces
    • Since excretion of the parasites is intermittent, it is best to carry out three different stool analyses before deciding upon a negative result.
    • it is easier to reveal the parasites in a stool obtained by means of a purgative medication or a laxative.