Metabolic Bone Disease in Reptiles
Metabolic bone disease (MBD) is a well recognized and all too common disease of reptiles. Other terms which may be used include fibrous osteodystrophy, osteomalacia, secondary nutritional hyperparathyroidism, osteoporosis, and rickets. There is no single cause and the disease is not as simple a calcium deficiency. However, the primary problem is a disruption of calcium metabolism which causes a host of related problems. MBD is almost always a result of poor husbandry, but generally preventable by providing a proper environment and diet. This is not always easy or inexpensive, but is vital to the health of pet reptiles. Discussions of this disease often involve iguanas. Because iguanas are very popular and are susceptible to MBD due to their specific diet/light/environment needs, there are a large number of cases seen in iguanas. Causes MBD is complex disease. In it's simplest terms, MBD results from an improper calcium to phophorus ratio in the body. Normally this ratio should be around 2:1 calcium:phosphorus (in the range of 1:1 to 2:1). When the calcium level is relatively low the body tries to compensate by taking calcium from wherever it can, for example the bones. This leads to a softening of the bones, making them susceptible to fractures and also leading to a deposition of fibrous tissue as the body tries to strengthen the bone in an absence of available calcium. Calcium also impacts a number of other physiological systems including muscle contraction (including the heart) and blood clotting. The 2:1 ratio of calcium to phosphorus that is ideal in the diet, but calcium metabolism is not that simple. Vitamin D (especially D3) is also vital to calcium metabolism, and because some reptiles do not absorb vitamin D that well (much like humans) they need ultraviolet light exposure to manufacture their own vitamin D. A full discussion of calcium, phosphorus, and vitamin D metabolism is beyond the scope of this article, but the basic factors that can skew the calcium:phosphorus ratio include: too little calcium or too much phosphorus (i.e. improper ratio) in the diet Signs and Symptoms: Vary depending on the severity and length of time over which the condition has developed. Due to the importance of calcium in bone formation and muscle function, most of the signs and symptoms are related to bone and muscle effects. These include: bowed, or swollen legs, or bumps on the long bones of the legs Prevention Proper husbandry is more than just the right diet. The following are important in both prevention and treatment: diet balanced in calcium and phosphorus, protein, energy and other nutrients
MBD Resources Calcium Metabolism and Metabolic Bone Disease by Melissa Kaplan |