ISSN 2398-2969      

Hypervitaminosis A

Clapis
Contributor(s):

Molly Varga

Anna Meredith

Synonym(s): Vitamin A toxicity


Introduction

  • Vitamin A Vitamin A is a generaly term for a large number of related compounds.
  • Retinol + retinal together are preformed vitamin A, which becomes retinoic acid in animal tissues.
  • Carotenoids are pigments formed by plants (beta-carotene being the most important); these compounds are converted to retinol within mucous membranes once eaten.
  • Retinol is stored in the liver bound to proteins (retinol binding proteins or RBPs) from where it is delivered to cells according to need.
  • Vitamin A is essential for bone development, maintaining epithelial integrity, reporduction and mounting an immune response.
  • Cause: excess vitamin A intake, possible iatrogenic overdose.
  • Signs: squamous metaplasia, kertainization of mucous membranes, pain/tenderness of bones/joints.
  • Diagnosis: hematology, biochemical evaluation, liver/kidney function tests, radiography.
  • Treatment: no specific treatment or antidote available. Stop access to feed containing vitamin A and vitamin A supplementation, rehydration, use of diuretics if hypercalcemic. Empirical treatment of seizures may be required. Vitamin E supplementation may be helpful.
  • Prognosis: long-term skeletal changes possible.

Presenting signs

  • Similar to those of deficiency and include squamous metaplasia and keratinization of mucous membranes.
  • Pain and tenderness of long bones and joints.
  • Cervical ventroflexion reported in other species.

Acute presentation

  • Significant acute overdose is very unlikely and has not been reported in the rabbit specifically; the potential for this to occur iatrogenically should be noted.
  • Extrapolating from other species, expected signs might include malaise, anorexia, weakness, possibly progressing to tremors, convulsions, paralysis and death.

Age predisposition

  • The effects of overdose are more severe in young animals as their ability to store vitamin A is reduced compared to adults.

Cost considerations

  • Potentially significant, especially in breeding colonies.

Special risks

  • Vitamin A maintains the integrity of epithealial surfaces, including mucous membranes; therefore, any organ system reliant on these will be functionally impaired in cases of overdose.
  • This includes the lungs, making anesthesia an increased risk, and the renal tubules therefore concomitant drug use should be approached with caution.
  • Vitamin A is often called the anti-infection vitamin and therefore individuals suffering from overdose may be at increased risk of infection due to the effects on epithelial integrity.

Pathogenesis

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Diagnosis

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • St Claire 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.
  • Frater J (2001) Hyperostotic polyarthropathy in a rabbit--a suspected case of chronic hypervitaminosis A from a diet of carrots. Aust Vet J 79 (9), 608-611 PubMed
  • DiGiacomo R F, Deeb B J & Anderson R J (1992) Hypervitaminosis A and reproductive disorders in rabbits. Lab Anim Sci 42 (3), 250-254 PubMed.

Other sources of information

  • Higdon J, Drake V J & Russell R M (2007) Vitamin A. Oregon State University, Linus Pauling Institute, Micronutrient Information Center. Website: lpi.oregonstate.edu.
  • Harcourt-Brown F (2002) Textbook of Rabbit Medicine. Butterworth Heinemann, UK.
  • McDonald P, Edwards R A, Greenhalgh J F D & Morgan C A (1996) Animal Nutrition. 5th edn. Longman, UK.
  • 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, USA. pp 321-333.
  • Gillett C S (1994) Selected Drug Dosages and Clinical Reference Data. In: The Biology of the Laboratory Rabbit. 2nd edn. Eds: Manning P J, Ringler D H & Newcomer C E. Academic Press, USA. pp 467–472.
  • 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, USA. pp 403-428.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!

 
 
 
 

To show you are not a Bot please can you enter the number showing adjacent to this field

 Security code