Lapis ISSN 2398-2969

Hypovitaminosis A

Synonym(s): Vitamin A deficiency

Contributor(s): Molly Varga, Anna Meredith

Introduction

  • Vitamin A   Vitamin A   is a general term for a large number or related compounds.
  • Retinol + retinal together make pre-formed vitamin A; this is metabolised to retinoic acid in animal tissue.
  • Carotenoids are pigments found in plants that can be converted to retinol within mucous membranes and stored in the liver bound to protein molecules (retinol binding proteins or RBPs).
  • Vitamin A is essential for bone development, maintaining epithelial integrity, reproductive function and the immune response.
  • Cause: vitamin A deficiency.
  • Signs: retarded growth/weight loss -> neurological signs; birth defects, keratitis.
  • Diagnosis: hematology, blood biochemistry, conjunctival swabs, fecal samples.
  • Treatment: offer correctly formulated diet, supplementation, treatment for ocular/neurological symptoms and coccidiosis.
  • Prognosis: good.

Presenting signs

  • Signs are similar to those of overdose   Hypervitaminosis A  ; squamous metaplasia of epithelial tissues.
  • Retarded growth and weight loss   Weight loss  are seen in growing animals, which may progress to neurological signs in severe cases.
  • Birth defects such as hydrocephalus and cerebellar herniation may be noted in neonates.
  • In adults, keratitis that progresses to iridocyclitis, hypopyon and blindness is a feature; however, the typical conjunctival swelling noted in other species is not seen.
  • In-breeding animals low fertility rates and abortion are noted.

Acute presentation

  • Rare as vitamin A stored in the liver.
  • Juveniles show reduced weight gain or loss and potentially neurological signs.
  • Adults typically exhibit keratitis.

Age predisposition

  • Both adults and juveniles are susceptible.

Cost considerations

  • Significant in breeding colonies due to significant reduction in reproductive potential as well as other clinical problems.

Special risks, eg anesthetic

  • None reported, however function of those organ systems lined with epithelium may be compromised.
  • Increased anesthesia risk if squamous metaplasia extends into the respiratory tract.
  • Concomitant drug use should be approached with caution as the gut, liver and kidney function can all potentially be affected.

Pathogenesis

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Diagnosis

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Treatment

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Prevention

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Sequelae

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Blomhoff R & Blomhoff H K (2006) Overview of retinoid metabolism and function. J Neurobiol 66 (7), 606-630 PubMed.
  • Schneider C (2005) Chemistry and biology of vitamin E. Mol Nutr Food Res 49 (1), 7-30 PubMed.
  • St Clair M B, Kennett M J & Besch-Williford C L (2004) Vitamin A toxicity and vitamin E deficiency in a rabbit colony. Contemp Top Lab Anim Sci 43 (4), 26-30 PubMed.
  • Collins M D & Mao G E (1999) Teratology of retinoids. Annual Rev Pharm & Toxicol 39 (1), 399-430 PubMed.
  • Tzimas G, Collins M D, Bürgin H et al (1996) Embryotoxic doses of vitamin A to rabbits result in low plasma but high embryonic concentrations of all trans-retinoic acid: Risk of vitamin A exposure in humans. J Nutr 126 (9), 2159-2171 PubMed.
  • Hennekens C H, Mayrent S L & Willett W (1986) Vitamin A, carotenoids and retinoids. Cancer 58 (8 Suppl), 1837-1841 PubMed
  • Fox R R, Eaton H D & Crary D D (1982) Vitamin A, betacarotene and hereditary buphthalmus in the rabbit. J Hered 73 (5), 370-374 PubMed.
  • McMichael H (1965) Inhibition of shope rabbit papilloma by hypervitaminosis A. Cancer Res 25 (7), 947-955 PubMed.

Other sources of information

  • Higdon J, Drake V J & Traber M G (2008) Vitamin E. Oregon State University, Linus Pauling Institute, Micronutrient Information Center. Website:http://lpi.oregonstate.edu/infocenter/vitamins/vitaminE.
  • Higdon J, Drake V J & Russell R M (2007) Vitamin A. Oregon State University, Linus Pauling Institute, Micronutrient Information Center. Website:http://lpi.oregonstate.edu/infocenter/vitamins/vitaminA
  • Harcourt-Brown F (2002) Textbook of Rabbit Medicine. Butterworth Heinemann.
  • McDonald P, Edwards R A, Greenhalgh J F D & Morgan C A (1996) Animal Nutrition. 5th edn. Longman.
  • Cheeke P R (1994) Nutrition and Nutritional diseases. In: Biology of the Laboratory Rabbit. 2nd edn. Eds: Manning P J, Ringler D H & Newcomer C E. Academic Press. pp 321-333.
  • Hunt C E & Harrington D D (1974) Nutrition and Nutritional diseases of the Rabbit. In: Biology of the Laboratory Rabbit. 1st edn. Eds: Manning P J, Ringler D H & Newcomer C E. Academic Press. pp 403-428.


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