ISSN 2398-2942      

Entamoeba histolytica

icanis
Contributor(s):

Vetstream Ltd

Synonym(s): E.histolytica


Introduction

Classification

Taxonomy

  • Phylum: Sarcomastigophora.
  • Subphylum: Sarcodina.
  • Order: Amoebida.
  • Family: Endamoebidae.
  • Genus: Entamoeba.

Active Forms

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Resting Forms

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Clinical Effects

Epidemiology

Habitat

  • Can be carried in the gastrointestinal tract of primates (including human beings) and dogs.
  • Dogs are not a significant reservoir of infection.

Lifecycle

  • After ingestion of the quadrinucleate cyst, the metacystic form is released and produces 8 uninucleate amoebae. These pass to the large bowel and may remain in the lumen or may invade the tissues.

Transmission

  • Cysts passed in human feces → transmitted in food and water, or by flies.
  • Cysts rarely formed in cats and dogs; therefore they are rarely infectious.

Pathological effects

  • Pathogenicity may be associated with host cell interaction with parasite causing release of phosphohydrolase from amoebic liposomes.
  • Presence of certain bacteria may also be active in pathogenesis.
  • Both invasive and non-invasive strains contain trypsin and pepsin.
  • Invasive strains invade epithelium, multiply and penetrate to submucosa where they spread laterally, causing ulceration.
  • Lesions may remain confined to the mucosa; repair may occur thus eliminating the organisms. Further penetration may occur with inflammation and neutrophil infiltration and spread may occur via the lymphatics and veins.
  • E. histolytica is commonly found in the right lobe of the liver where an abscess may develop; this may be acute or chronic.
  • Abscesses may also occur in the lungs and brain and rarely the skin.
  • Natural infections have occurred in dogs and cattle, acquired from human contacts.
  • The organism commonly occurs in Old World monkeys.
  • Wild rats may harbor the organism with or without signs of disease; the organism is probably derived from humans.

Control

Control via chemotherapies

Control via environment

  • Good sanitation, sewage disposal, avoidance of contamination of food and clean water supply.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Meloni B P, Thompson R C, Hopkins R M et al (1993) The prevalence of Giardia and other intestinal parasites in children, dogs and cats from aboriginal communities in the Kimberley. Med J Aust 158 (3), 157-159 PubMed.
  • Nogami S, Inoue I, Araki K et al (1991) Specificity of commercially available Entamoeba histolytica antigen in enzyme-linked immunosorbent assay (ELISA) to sera from dogs with various parasitic infections. J Vet Med Sci 53 (4), 729-731 PubMed.
  • Wittnich C (1976) Entamoeba histolytica infection in a German shepherd dog. Can Vet J 17 (10), 259-263 PubMed.

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