Metabolic Bone Disease (MBD) is unfortunately a common disease of reptiles due to lack of dietary calcium, imbalanced nutrition and/or lack of UVB rays. UVB rays from either unfiltered sunlight or a UVB producing bulb are needed in reptiles to produce Vitamin D3 in the skin, which is necessary to absorb calcium from the food and supplementation. Without UVB rays then your chameleon cannot absorb the calcium you are giving it. If you are not providing an adequate level of calcium in the diet then no amount of UVB will make up for it. Too high levels of phosphorus in the diet will interfere with calcium absorption so even with good calcium levels and UVB the body is still not getting enough. There are many body processes that require calcium, such as muscle contraction, energy metabolism, intestinal movement, nerve conduction, blood vessel function, and bone strength. To compensate for inadequate calcium absorption the body will pull calcium directly out of the bones where it is stored so there is enough calcium for critical functions like muscle movement and metabolism. This causes the bones to be very weak, even to the point of bending or breaking very easily. Chronic calcium deficiency causes continued damage to multiple organs, eventual organ failure and death. Lack of sufficient calcium for muscle movement can lead to constipation and very often egg binding in females, which is life threatening in itself. Due to the calcium deficiency affecting entire body in drastic way these chameleons can easily develop concurrent illnesses, such as respiratory infections, eye infections, etc. Calcium needs are the highest during the first year of life while bones are still growing so it is often young chameleons that are most affected. There are rare cases of metabolic disease occurring despite proper calcium and UVB and a congenital component is suspected, though not confirmed. Almost every instance of MBD can be completely attributed to deficiency in care.
By the time symptoms of metabolic bone disease are apparent the disease is already advanced and there is a severe calcium deficiency. Signs of MBD include stunted growth, bent legs bones, fractures of those bones (double elbows or knees), weakness, falling off branches, grabbing at its own legs, tongue not shooting as far, a 'rubber' jaw, the mouth doesn’t close all the way, etc. The most notable symptoms are bent legs and multiple elbows or knees, which are actually fractures of the leg bones. Bloodwork will show an elevated phosphorus level that may be the same or higher than the calcium level, which is abnormal. There may also be evidence of other organ damage, especially with the kidneys. On x-rays the bones will appear to have poor density and may not even be visible in the end stages because there is so little calcium left.
Examples of bone deformities and fractures from MBD:
Metabolic bone disease does not happen over a course of days. It takes weeks to months of persistently inadequate care to cause the symptoms associated with calcium deficiencies. It is very important to take action as soon as symptoms are recognized as the disease is already in the advanced stage. Damage caused by metabolic bone disease cannot be reversed completely but the disease process can be stopped so there is not further damage and the bones can heal if proper UVB is supplied and the imbalance of dietary calcium is addressed.
Metabolic bone disease takes a long time to develop, and conversely takes a long time to resolve. Correcting your husbandry and providing adequate calcium, nutrition through gutloading
, and UVB is the first critical step. However, the deficit of calcium needs to be addressed with additional supplementation before the body can function normally and begin to heal. A small drop of liquid calcium (without D3) can be given twice daily for a month to replace the calcium deficit. A vet may have to give injectable calcium to replace the deficit in more than mild cases. UVB, especially in the form of unfiltered sunlight, is essential. Force feeding may be required to nurse a weak, very ill chameleon back to health. If there are broken bones already unfortunately they will need time to heal on their own because if a cast or splint is applied it can actually cause more breaks to occur since the bones are so weak. A hospital cage that is shorter with wider perches and a towel on the bottom to cushion falls should be provided to prevent further injury. It is very important to address MBD as soon as symptoms are noticed to stop the damage being done. Sometimes symptoms are so severe that chameleons will not survive, despite aggressive treatment, due to permanent organ damage. But some chameleons can make truly remarkable recoveries from severe MBD with a lot of intensive care.
This severe case was able to make an almost complete recovery 8 months later:
Despite successful recoveries there may be permanent damage even many years later:
#1: Chameleon with Metabolic Bone Disease resulting in poor bone density.
#2: Chameleon with good bone density but residual damage from MBD when he was young.
#3: Normal chameleon skeleton with good bone density.
The deformities on #2 are indicated by the yellow arrows, where the bones are deformed and partially collapsed, even 3 years after recovering. Compare this to the blue arrow on #3 - that is what the arm bones are supposed to look like: straight and apart.
Bones show up white on x-rays due to minerals, like calcium, in bones. When that is missing the bones do not show up very well on x-rays. If you look at the skulls of the three chameleons it is apparent how much better you can see every bone in #2 and 3. Also take a look at the arms of #1 - how many toe bones can you count? I cannot even see any bones at all in the left arm, and in the right I still can't tell you how many there are. It is hard to see any of the vertebral bones and even the ribs are hard to count. The bones should look like #2 and #3 where you can see all of them with good detail and be able to count them. Lack of proper bone density is a classic indicator of calcium deficiency, and can quickly lead to pathologic fractures where the bones are so weak that they break just under the weight of the chameleon. While some x-rays can turn out poorly due to technique and can be improved by enhancing certain settings on the x-ray machine, in a case of MBD you will not be able to make the bones show up any better regardless of technique because the mineral to make them show up is simply not there.
The only way to prevent Metabolic Bone Disease is to start from the beginning with good husbandry, optimal nutrition through gutloading, adequate UVB, and appropriate calcium supplementation.