Metabolic Bone Disease In Reptiles
Nutritional secondary hyperparathyroidism, commonly called metabolic bone disease (MBD), is one of the most common diseases affecting reptiles. In most cases, it is easily preventable with the provision of proper lighting and diet.
MBD is typically seen in basking reptiles. These reptiles are usually diurnal (awake during the day) animals and eat primarily an insect or plant-based diet. Please ask if you are unsure whether your reptile is a basking species.
Reptiles, like other animals, require vitamin D in order to absorb and metabolize calcium, a very important mineral to normal body function, as well as other minerals. Basking reptiles make vitamin D in their skin when it is exposed to a specific range of beta ultraviolet (UVB) rays in sunlight. If they are not exposed to these UVB rays, they cannot make vitamin D and thus cannot absorb calcium from the food they eat. Over time, as their body becomes calcium depleted, calcium is taken from the only other source, the bones. As bones lose their calcium, they become soft, bow and swell, and break easily. These changes are very painful and impair normal activity and movement. In some cases, spinal fractures may develop causing the animal to become paralyzed. As total body calcium is depleted, affected animals may also become weak, have muscle twitching, develop cloacal prolapse, or gravid females may become egg-bound.
While many cases of MBD may be treated and fractures healed with intensive supportive care and husbandry correction, any bowing or swelling of the bones is permanent. In advanced cases, the damage may be significant enough to be fatal.
The best way to avoid MBD is to prevent it from occurring in the first place. Allowing your basking reptile access to direct, unobstructed sunlight (taking them outside and placing them directly in the sunlight) is the ideal way to provide UVB light. If you take your reptile outside, however, you must make sure that it is enclosed so that it cannot escape, is safe from predators, and that the temperature is not too hot or too cold. Your reptile will also need access to shade to allow for thermoregulation. Do not place any solid structures such as glass between the sun and your reptile or the UVB rays will be filtered out and never reach your animal.
Alternatively, you may purchase a UVB bulb at your local pet store or online pet supply store to place over your reptile’s indoor enclosure. These bulbs are different from heat bulbs and are usually more expensive. Zoo Med’s Reptisun 5.0 is an example of a light that emits UVB rays in the proper wavelength range. These bulbs must be replaced every 3-6 months, even if they are still working because the UVB rays are no longer emitted after this period of time. Remember, there cannot be any glass, plastic or other solid surface between the bulb and your reptile, or the UVB will be filtered out. Also, the UVB rays only extend approximately 2 feet from the lamp, thus your enclosure must be set up so that your reptile spends most of its time within 2 feet of the bulb.
Reptiles may still develop MBD despite proper provision of vitamin D if their diet is deficient in calcium. Please refer to specific handouts for nutrition recommendations for your reptile. You may also refer to www.anapsid.org online for excellent diet recommendations specifically for your species of reptile. Additionally, reptile calcium and vitamin supplements are available and may be used to dust prey or to sprinkle over food. Reptical, Herptivite, and Miner-All (no vit D) are examples of good supplements.
If you have any questions regarding correct lighting, diet, or supplements, or if you are worried that your reptile may have MBD, please don’t hesitate to call and ask for help.