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Tuesday, December 7, 2010

Exotics Week: Metabolic Bone Disease

Continuing with reptiles, let's take a look at another completely preventable condition in captive reptiles...metabolic bone disease.  This disorder involves a lack of proper bone absorption of calcium, resulting in a serious health condition. Though it's primarily seen as a problem in the bones, calcium is also involved in proper muscle contraction so you can see muscle problems as well.

Proper calcium metabolism requires two parts.  First is taking in enough calcium.  Reptiles must be fed specific calcium-rich fruits and vegetables, especially dark green leafy vegetables (kale, spinach, mustard greens, collard greens, etc.).  It's sometimes surprising how many people don't realize that many pet reptiles are mostly herbivores and don't need much in the way of insects as meals.  When those insects are fed, or if the reptile is mostly a carnivore, the prey should be properly prepared.  This can be done by "gut loading", or feeding the prey a nutritionally rich food.  The idea is that when the reptile eats its prey it also ingests the nutrition in that meal's digestive tract.  The other way to properly prepare food is to "dust" it with a calcium powder that can be purchased in any pet store that sells reptile supplies.  No matter how it is accomplished, there must be plenty of calcium in the diet.

However, you could feed nothing but calcium and still have a problem if there isn't proper lighting.  In order for calcium to make it into tissues and bones the body needs vitamin D3.  If there is a deficiency of this vitamin then all the calcium in the world won't do much good.  The body naturally produces this vitamin when stimulated by ultraviolet light.  This is the main reason why you need a full spectrum UV light in any reptile enclosure.  The package of the bulb will state if this is the case, and you should look for statements like "full spectrum UV" or "UVA and UVB".

There are other factors in metabolic bone disease, including kidney and liver disease, too much phosphorous in the diet, or environmental factors that may impair calcium absorption.  But in my experience the biggest reasons for this disorder are diet and lighting.
This is a gradual onset that may not be obvious in the early stages.  But by the final stages these are very sick reptiles and can die if not treated quickly.  Here is a list of the most common symptoms:
  • bowed or swollen legs, or bumps on the long bones of the legs
  • arched spine or bumps along bones of spine
  • softening and swelling of the jaw, sometimes called "rubber jaw"
  • tremors or jerky movements
  • lameness
  • lack of appetite
  • constipation
  • fractures of the bones due to bone weakness
  • lethargy, weakness and even partial paralysis (sometimes unable to lift body off ground)
Treatment usually involves changing the causative factors, improving diet, housing, and lighting.  With seriously ill reptiles they may also need vitamin injections or supplements.  With aggressive supportive care there is a chance of saving them.

Remember yesterday how I said that many common health problems can be prevented with proper care?  Don't forget that.  Like vitamin A deficiency, metabolic bone disease is completely preventable and should rarely happen with properly cared-for reptiles.