Entamoeba infections

• Amoebiasis


  A disease caused by Entamoeba histolytica

  
• Protozoa


  A diverse group of unicellular eukaryotic organisms
• Sarcodina

  A subphylum of protozoa that includes amoebas
• Trophozoites

  The active, feeding stage of amoebas
• Cyst


  A dormant, resistant stage of amoebas
• Objectives

  • Classification
  • Morphology
  • Transmission
  • Clinical Presentation
  • Diagnosis
  • Treatment
• Classification of Entamoeba histolytica

  • Phylum Sarcomastigophora
  • Subphylum Sarcodina
  • Super Class Rhizopoda
  • Class Lobosea
  • Sub Class Gymnamoebia
  • Order Amoebida
  • Suborder Tubulina

  
• Trophozoite morphology

  • Irregular shape with pseudopodia
  • Large 20-30µm in diameter
  • Nucleus characterized by a peripheral layer of chromatin ring and a central karyosome

  
• Cyst stage morphology

  • Oval or spherical in shape
  • Presence of 4 nuclei (mature) and 1-2 (immature)
  • Karysome is compact and usually centrally located
• Entamoeba histolytica has a worldwide distribution
• Entamoeba histolytica is endemic in most tropical countries with low socio-economic conditions
• Entamoeba histolytica is the third leading parasitic cause of death after Malaria and Schisto
• High risk groups for amoebiasis

  • Travelers
  • Immigrants
  • Sexually active homosexuals
  • Individuals in mental institutions
  • Prisoners
  • Children in day care centers
  • Immunocompromised individuals
• Infection among HIV AIDS patients in Ghana is 14%
• Severe infections are common in

  • Children below the age of 5 years
  • Pregnant women
  • Malnourished individuals
  • Individuals taking corticosteroids
• Transmission

  Oro-faecal through food or water contamination<|>Sexual (oro-anal) transmission
• Reservoirs are the asymptomatic cyst carriers (humans)
• Incubation period ranges from 2-4 weeks
• Entamoeba histolytica usually found in the large intestines in the mucosal lining
• Clinical manifestations of amoebiasis

  • Sudden onset with abdominal discomfort
  • Diarrhoea with blood or mucus
  • Tender abdomen
  • Liver slightly enlarged
  • Ulcers may perforate and cause peritonitis
• 90% of infections are intestinal (Amoebic Colitis)
• 90% of infections are asymptomatic
• 10% of infections are symptomatic
• 10% of infections are extra intestinal (Amoebic Abscesses)
• Pathogenesis

  • Can destroy all human tissues
  • Preferred sites are intestinal mucosal, liver, brain, skin
  • Trophozoites can invade cartilage & bones
  • Feed on blood and form abscesses
• Enzymes are believed to lyse host tissues leading to amoebic ulcers
• Ulcers often develop in the caecum, appendix or adjacent portion of the ascending colon
• Ulcers are usually raised with a small opening on the mucosal surface and a larger area of destruction below the surface
• Extraintestinal Amoebiasis


  • Amoebic liver abscess
  • Pleuropulmonary amoebiasis
  • Genitourinary amoebiasis
  • Cutaneous amoebiasis
  • Cerebral amoebiasis
• Amoebic liver abscess is the most common extra-intestinal infection
• Amoebic liver abscess is found in all age groups but is 10x more common in adults
• Most of those infected (20%) have histories of amoebic dysentery
• 10% of patients have diarrhoea or dysentery at the time of diagnosis of the abscess
• Amoebic liver abscess symptoms

  • Sudden onset with pain in upper abdomen
  • High fever
  • Profuse sweating
  • Anorexia
  • Weight loss
  • Nausea
  • Vomiting
  • Fatigue
  • Hepatomegaly
• In typical abscesses, the fluid is odourless resembling chocolate syrup or anchovy paste and bacteriologically sterile
• Diagnosis methods

  • Microscopy
  • Culture methods
  • Serological methods
  • Sigmoidoscopy
  • Polymerase Chain reaction
• Treatment drugs

  • Luminal amoebicides
  • Tissue amoebicides
• Luminal amoebicides

  • Diloxanide furoate
  • Iodoquinol
• Tissue amoebicides

  • Metronidazole
  • Dehydroemetine
  • Chloroquine
• Prevention and Control

  • Good sanitation practices
  • Proper food handling
  • Boiling/filtering of water
  • Avoidance of vegetables grown on soils with human excreta as fertilizer
  • Soaking salad leaves in vinegar & 50% acetic acid
  • Health education