A Primer On Metabolic Bone Disease In Reptiles

Metabolic bone disease (MBD) is one of the most common diagnoses in our reptile patients, but what, exactly, is it?

The Role of Calcium In Metabolic Bone Disease in Reptiles

To understand metabolic bone disease in reptiles, an understanding of calcium is necessary. Calcium plays many roles in the body of a reptile. Muscles, including the heart, need calcium to contract. Calcium has an important role in blood clotting. The bones are mostly composed of calcium. The list goes on. Obviously, calcium is important, and deficiencies can lead to problems related to any or all these vital functions.

If a reptile experiences hypocalcemia (low blood calcium), its parathyroid glands will be stimulated to produce the parathyroid hormone (PTH). This hormone encourages the breakdown of bone, raising the blood calcium level but harming bone density in the process.

Learning Point: Metabolic bone disease is just a description of the symptoms of prolonged periods of low blood calcium (hypocalcemia).

Why Might Blood Calcium Be Low In Your Reptile?

Dietary deficiency can certainly lead to hypocalcemia. Reptiles’ calcium intake might be insufficient if their prey items are not appropriately fed, or “gut-loaded,” and/or if a good quality calcium supplement is not used to dust food items. Diets high in phosphorus can also result in hypocalcemia as excessive phosphorus binds calcium, rendering it unusable.

Another reason for hypocalcemia in reptiles is failure to absorb ingested calcium from the gastrointestinal tract into the blood. To do so requires Vitamin D3, and reptiles require UV-B radiation to make this vitamin. Failure to provide a good quality UV-B source will lead to Vitamin D3 deficiency and an inability to use the calcium provided in the diet.

Snakes and other carnivorous reptiles that eat whole prey (think mice, rats, etc.) rarely suffer from MBD because they get sufficient calcium and Vitamin D in the diet. MBD is, however, a common problem in insectivorous, herbivorous, and omnivorous species like water dragons, bearded dragons, iguanas, and box turtles.

When hypocalcemia develops secondary to dietary deficiency or inability to use calcium due to insufficient Vitamin D3, the disease process that develops is most accurately described as nutritional secondary hyperparathyroidism (NSHP). Some authors call this nutritional MBD.

MBD may also occur due to renal secondary hyperparathyroidism (RSHP). Renal refers to the kidneys, and this form of MBD is seen in cases of reptile kidney disease or kidney failure. This can be seen in older reptiles, those being fed excessively high levels of protein, or in patients where gout is affecting the kidneys’ function.

What Are The Clinical Signs of Metabolic Bone Disease In Reptiles?

When should one suspect MBD in his or her reptile pet? Reptiles affected by MBD can exhibit a wide variety of clinical signs related to the variety of functions calcium serves in the body.

Symptoms of MBD may be nonspecific, such as lethargy, weakness, or failure to eat. Shaking or tremors can be seen due to calcium’s role in muscle contractions. Limping or failure to use one or more limbs can be seen due to weakened or fractured bones, due to reduced bone density. Swelling of the jaw or limbs can be seen as the body attempts to stabilize weak or fractured bones by laying down fibrous material—this is called fibrous osteodystrophy. Deformities of the shell can be seen in tortoises and turtles.

How To Diagnose Metabolic Bone Disease In Reptiles

If any of the above clinical signs are seen, you should see your reptile veterinarian. The first step should be a discussion about husbandry: the day-to-day care of your pet. To determine the underlying cause of MBD, your veterinarian will need to understand how your pet is housed, what he or she is fed, and what, if any, supplements you are using at home. So, it’s important to be honest and thorough in your responses to questions about husbandry. Blood work and radiographs (X-rays) also may be helpful in making a diagnosis.

How To Treat Metabolic Bone Disease In Reptiles

Not surprisingly, calcium deficiency related to inappropriate nutrition typically is addressed by improving the diet and/or prescription of a calcium supplement, typically oral calcium glubionate. The most common husbandry-related reason for calcium deficiency is inappropriate or absent UV-B lighting. A good quality full spectrum UV bulb will be recommended, and this bulb needs to be replaced at a minimum every 6 months.

Critically ill patients require hospitalization for supportive care, including calcium supplementation, nutritional support, fluid therapy, heat support, and pain management.

What’s the Prognosis For Reptiles With Metabolic Bone Disease?

Many patients with metabolic bone disease can recover with appropriate treatment and dedicated efforts to improve husbandry, but recovery often takes weeks-to-months.

How To Prevent Your Reptile From Developing Metabolic Bone Disease

A good understanding of your reptile’s needs can help you avoid MBD. But figuring out just what those needs are could feel like a daunting task. Social media, YouTube, and Google searches may provide conflicting information. Older print publications may be outdated and poorly reflect our current level of knowledge. At Alford Avenue Veterinary Hospital, we offer comprehensive medical care for reptiles as well as husbandry consultations. Our goal is to provide accurate, easy-to-understand instructions for the care of your pet. If you’re thinking about buying or adopting a reptile, ask us about its care requirements before you make the decision to add a new pet—and new set of responsibilities—to your home.

Need help with metabolic bone disease in reptiles? Contact Alford Avenue Veterinary Hospital for consultation & treatment of your reptile.