Exotis ISSN 2398-2985


Hypovitaminosis A

Synonym(s): Vitamin A deficiency (VAD)

Contributor(s): Vetstream Ltd, Allan Muir

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  • Cause: typically caused by a lack of dietary vitamin A. This common condition can be seen in a range of reptilian species, however it is usually associated with aquatic chelonian and insectivorous lizard species.
  • Signs: bilateral periocular edema, secondary bacterial conjunctivitis, skin lesions, secondary bacterial infections of the gastrointestinal and respiratory tract, aural abscessation, hyperkeratosis of the beak (chelonian), chronic respiratory infections, renal failure in severe cases.
  • Diagnosis: biopsy, cytology, history, clinical examination.
  • Treatment: vitamin A supplementation, correction of underlying husbandry deficits, topical/systemic antibiosis, topical analgesia.
  • Prognosis: variable.
Print off the Owner Factsheets on Nutritional diseases in chameleons, Nutritional diseases in geckos, Nutritional diseases in lizards, Nutritional diseases in snakes, Nutritional diseases in terrapins and/or Nutritional diseases in tortoises to give to your clients.



  • Hypovitaminosis A causes multifocal squamous cell metaplasia and hyperkeratosis in a range of body tissues; therefore it is important to remember that his condition is not specific to the eye.
  • Deficiency in vitamin A can affect glandular mucous membrane epithelium within the reptilian body, including the respiratory and digestive tract.
  • It was nearly 50 years ago that Dr Edward Elkan and Dr Peer Zwart independently identified hypovitaminosis as the cause of the conjunctival changes seen in aquatic chelonian with poor nutritional status.
  • Their histopathological studies demonstrated epithelial changes in conjunctiva and orbital glands which were characteristic of low vitamin A levels.
  • Hypovitaminosis A is particularly obvious in terrapins because of the large proportion of the orbit occupied by the lacrimal and Harderian glands.
  • Lizards generally have a ventromedial Harderian gland and a dorsotemporal lacrimal gland, but these are considerably smaller than in the freshwater aquatic chelonia.
  • Geckos, chameleons and snakes have only a well-developed Harderian gland, but even this does not rival the size of the chelonian orbital glands.
  • The desquamated hyperkeratinized epithelium swells the conjunctiva and fills the orbit.

Predisposing factors


  • A diet deficient in vitamin A Vitamin A, in the case of terrapin/turtle species these animals are often being fed on a whole meat/shrimp diet without any commercial pellets or supplementation Nutritional requirements.
  • In the case of the insectivorous lizards, often the owners are failing to dust the insects in a suitable supplement containing vitamin A and/or failing to “gut load” the insects prior to feeding.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Mans C & Braun J (2014) Update on common nutritional disorders of captive reptiles. Vet Clin Exotic Anim Pract 17 (3), 369-395.

Other sources of information

  • Ballard B & Cheek R (2017) Exotic Animal Medicine for the Veterinary Technician. 3rd edn. Wiley-Blackwell.
  • Girling S J (2013) Veterinary Nursing of Exotic Pets. 2nd edn. Wiley-Blackwell.
  • Mader D R & Divers S J (2013) Eds Current Therapy in Reptile Medicine and Surgery E-Book. Elsevier Saunders, USA.
  • Williams D (2012) The Reptile Eye. In: Ophthalmology of Exotic Pets. Wiley-Blackwell, UK. pp 167-169.
  • Calvert I (2004) Nutritional Problems. In: BSAVA Manual of Reptiles. 2nd ed. BSAVA, UK. pp 289-308.

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, and David L Williams: Ophthalmology of Exotic Pets © 2012, published by John Wiley & Sons.