ISSN 2398-2985      

Amebiasis

Jreptile
Contributor(s):

Wiley Blackwell

Mark Rowland

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Synonym(s): Entamoebiasis, Entamoeba infection


Introduction

  • Cause: infection with the ameba Entamoeba invadens.
  • Signs: diarrhea, anorexia, dehydration, weight loss, seizures.
  • Diagnosis: fecal examination, direct saline smear, culture, immunohistochemistry (snakes).
  • Treatment: antiprotozoals.
  • Prognosis: guarded to poor.
  • Many protozoans inhabit the gastrointestinal tract of lizards and tortoises as non-pathogenic or commensal organisms.
  • Entamoeba invadens lifecycle:
    • Passing of infective cysts from a host.
    • Ingestion of cysts by a suitable host.
    • Multiplication in to trophozoites in the intestinal tract.
    • Invasion of trophozoites in to host tissues.
    • Potential for bacterial septicemia via intestinal compromise.
    • Formation of infective cysts.
    • Shedding of infective cysts.
  • The lifecycle is direct; that is, spread directly from one reptile to another via the feco-oral route.

Pathogenesis

Etiology

  • Infection with the ameba Entamoeba invadens.
  • The pathogenesis of clinical disease is multifactorial and is caused by the tissue invasion of trophozoites and cellular destruction, and from secondary bacterial infection.
  • This ameba causes very high mortality and morbidity in snakes and is transmitted via the ingestion of infected reptile feces.
  • Entamoeba invadens is an example of an ameba that causes low morbidity in tortoises but can cause severe illness and death in snakes and carnivorous lizards.
  • Entamoeba invadens also causes acanthamoebic meningoencephalitis, primarily in snakes, causing fits and opisthotonic seizures; treatment is generally unsuccessful.

Predisposing factors

General

  • Keeping tortoises and carnivorous lizards and snakes in the same environment.
  • Inappropriate hygiene.

Pathophysiology

  • Amebiasis is directly transmitted by a fecal-oral route in reptiles and is pathogenic and highly virulent to snakes and some lizards. It is important to note that Entamoeba invadens is potentially a pathogen in all reptiles.
  • Of the many species of amebae that are found in snakes, E. invadens is the most pathogenic.
  • Amebiasis is non-pathogenic in tortoises and crocodilians but may be transmitted by both via their feces.
  • After incubating in the lining of the small intestine, each infective cyst produces eight uninucleate amebae which invade cells lining the large intestine of the same snake.
  • The amebae may also penetrate into the bloodstream and so end up in the liver, causing hepatic necrosis. The bile duct is another route to the liver for the pathogen.
  • Chelonia can be subclinical carriers of pathogenic ameba species.

Timecourse

  • Variable.

Epidemiology

  • Keep chelonia in a separate enclosure.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

Other sources of information

  • Cheek R & Crane M (2017) Snakes. In: Exotic Animal Medicine for the Veterinary Technician. 3rd edn. Eds: Ballard B & Cheek R. Wiley-Blackwell. pp 137-181.
  • Rivera S (2017) Chelonians. In: Exotic Animal Medicine for the Veterinary Technician. 3rd edn. Eds: Ballard B & Cheek R. Wiley-Blackwell. pp 183-196.
  • Wilson B (2017) Lizards. In: Exotic Animal Medicine for the Veterinary Technician. 3rd edn. Eds: Ballard B & Cheek R. Wiley-Blackwell. pp 95-136.
  • Girling S J (2013) Common Reptile and Amphibian Diseases. In: Veterinary Nursing of Exotic Pets. 2nd edn. Wiley-Blackwell. pp 297-318.
Reproduced with permission from Bonnie Ballard & Ryan Cheek: Exotic Animal Medicine for the Veterinary Technician © 2017, Simon J Girling: Veterinary Nursing of Exotic Pets © 2013, published by John Wiley & Sons.

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