Metabolic Bone Disease in Iguanas

Metabolic bone disease is a common problem in pet iguanas.  In captivity, it is difficult to provide these sun-loving lizards with enough exposure to sunlight.  Without sunlight and the vitamin D3 that comes with it, iguanas cannot properly absorb and metabolize calcium from their diets.  The body steals calcium from bones to make up for the discrepancy.  When I x-ray an iguana with metabolic bone disease, the bones are gray ghost-like images that don’t show up well instead of the normal dense white bones. 

The common clinical signs seen with metabolic bone disease are;
1) Fractures of the long bones and swelling around the fracture.
2) Swollen jaws that feel rubbery to the touch.  This condition is called ‘rubber jaw’.
3) The inability to move the rear legs because of fractures to the back or pelvis.  When these fractures heal, the spinal column is often distorted in shape causing the iguana back pain.
4) Constipation that may be caused by spinal or pelvic fractures.  I have also seen constipation in iguanas without fractures that resolves shortly after calcium therapy is started.  I believe the lack of calcium causes gut motility problems as well as interfering with skeletal muscle contractions.
5) Anorexia.
6) Muscle fasciculations or twitching that occurs when the level of calcium in the blood is low.  It almost looks like their skin is crawling.  Iguanas with muscle fasciculations with die without immediate treatment.

The basis of treatment is correcting the calcium deficiency as quickly as possible.  Initially, the iguana is hospitalized for injections, tube feedings and an enema.  Once the patient is eating again, the iguana may go home on oral supplements although frequent rechecks are needed to make sure they are getting adequate amounts of nutrition.  Unfortunately, few iguanas with advanced disease will survive.  If they do, they often suffer from chronic back pain and require specially designed cages with ramps to move around. 

The good news is that metabolic bone disease is preventable with good husbandry.  Here are my tips:
1) Change full spectrum light bulbs frequently to insure that the UV spectrum is working.  The UV spectrum burns out well before the visible light spectrum of radiation so the bulb ‘turning on’ does not mean it is working.
2) The iguana must be within 18 inches of the bulb to absorb the UV radiation. 
3) I recommend 12 hours of UV radiation a day.  Make sure the iguana actually stays under the bulb by placing it over their favorite perch or providing several bulbs to cover the entire cage. 
4) Feed a well balanced diet that has the proper ratio of calcium and phosphorous.

Published by kristennelsondvm

Dr. Kristen Nelson grew up on a farm in Watertown, Minn., where she developed a deep love for animals of all kinds. She received a Doctor of Veterinary Medicine degree from the University of Minnesota, College of Veterinary Medicine. Kris then completed a small-animal internship at the prestigious Animal Medical Center in New York City. In addition to writing and speaking, she cares for small and exotic animals in Scottsdale, Az. Dr. Nelson is widely quoted in the media. Her credits include Ladies’ Home Journal, USA TODAY, the Los Angeles Times and numerous radio and television interviews. Dr. Nelson has written two books, Coated With Fur: A Vet’s Life and Coated With Fur: A Blind Cat’s Love. Kris and her husband Steve share their home with rescued cats, birds and a dog.