Metabolic Bone Disease


General Husbandry, Health Issues - Posted on 23 Dec 2013 by admin-blog

What is MBD?

Mader, D.R., 2006. Metabolic Bone Disorders – Reptile Medicine and SurgeryMetabolic Bone Disease (MBD) is a name given to a group of conditions that are unfortunately widespread in the reptile trade. MBD primarily affects the bone structure, often weakening it, making it prone to fractures and breaks. MBD most commonly occurs in lizards and chelonians but can affect snakes too. If left untreated, it is usually fatal, either directly or indirectly. Catching MBD early is key to ensuring that the animal survives and that less permanent damage is done as many of the effects of MBD are non-reversible.

 

Causes

There are many potential triggers for MBD, though most are related to inadequate husbandry. The most common cause for MBD is a lack of dietary calcium or vitamin D3, a calcium: phosphorous ratio of less than 1:1, or lack of suitable UV lighting. In addition, inadequate temperatures can prevent proper digestion and stress can also play a role in causing the onset of MBD.

 

Avoiding MBD – Prevention is Better Than the Cure!

Mader, D.R., 2006. Metabolic Bone Disorders – Reptile Medicine and SurgeryUnder natural conditions, reptiles synthesize their own vitamin D by using UV (290-320nm) to convert cholesterol to an inactive form of vitamin D, which is then converted to a chemical called Calcitriol. Calcitriol increases the amount of calcium absorbed from food items in the gut allowing it to be used by the body such as for muscle movement and bone development or reinforcement.

Whilst natural sunlight is best, most of the useful wavelengths of sunlight are filtered out by glass and a short runaround in the garden on a summer’s day is not enough. Therefore, artificial lighting is the only option. There are many UV tubes out there and you need to make sure you get one that is suitable for your animal. Some of the best on the market are the T8 tubes produced by Arcadia. For most lizards and chelonians a tube of 10%-12% is best. In some circumstances, a lower % may be used. See our UV Caresheet or specie specific caresheets for more info.

NutrobalA proper diet is key to avoiding MBD. All lizards and chelonians of all ages require a vitamin supplement to be added to their food on a routine basis (approx. every other meal). Nutrobal is one of the best available and contains calcium, D3, as well as vitamins A,C,E,K,B1,B2,B6,B12 and essential minerals more info here. A varied diet is vital to ensuring that your animal gets all the nutrition it requires. For insectivorous reptiles, a variety of insects should be used. For herbivorous reptiles, high quality vegetables such as spring greens, curly kale, rocket are ideal. Cabbages, spinach and some members of the brassica genus should be avoided as they contain a chemical which binds to calcium in the blood.

As mentioned above, correct temperatures are essential in allowing your reptile to digest its food properly. Low temperatures will cause digestive enzymes to slow down resulting in poor digestion of food and reducing the amount of nutrition absorbed by your animal. The best way of maintaining suitable temperatures is through the use of a Thermostat (not to be confused with a thermometer). Thermostats connect to your primary heat source – usually a heat bulb and will adjust the power sent to It accordingly, to maintain a chosen temperature. For more info have a quick read of our Thermostat care sheet.

Finally, limiting stress is a key factor, not just in limiting the risk of MBD but for the general well-being of your reptile. This is a complex issue to cover but ultimately can be addressed by providing your animal with a suitable environment. Have a look through our care sheets to see if we have one for your animal or give us a call for advice.

 

Signs and Symptoms

If a reptile is not receiving adequate calcium from its diet it must get it elsewhere. Their bodies produce a hormone which stimulates the breakdown of bone tissue to release calcium back into the blood. This gradually weakens the bone structure resulting in fragile bones which fracture or break.

Mader, D.R., 2006. Metabolic Bone Disorders – Reptile Medicine and SurgeryIn lizards and amphibians, one of the earliest signs of MBD is “Rubber Jaw”. Rubber jaw is the softening of the lower jaw which causes deformities and can make eating difficult. To check for rubber jaw, apply gentle pressure on the lower jaw of the animal to see if the jaw is rigid and firm. If the jaw bends slightly this is characteristic of rubber jaw. In tortoises, softening of the shell is commonly seen early on in MBD. As above, applying gentle pressure on the shell to check that it is rigid and firm can detect the presence of MBD.

Other early symptoms may include:

  • Swelling of arms/legs/jaw
  • Inability to Raise body off floor
  • Prolapse
  • Anorexia
  • Stunted Growth
  • Eating Substrate

Reptiles with MBD often show muscle spasms. This can present itself as a kind of shivering of the whole body which can be felt when being held or as tremors of legs, arms and head.

 

Treatment

Reptile VetIf MBD is suspected, proper diagnoses and then treatment by a vet should always be sought. In addition to veterinary treatment, it is essential that any environmental or nutritional causes for MBD be resolved, otherwise the veterinary treatment will be useless.

With proper treatment and correction of any environmental or nutritional factors, the calcium deficiency and MBD can be corrected. However, many of the effects of MBD will be permanent, such as bone deformities – which is why preventing MBD is so important. This article only really scratches the surface of MBD and for more info see us in store.

 

Refs

  1. Mader, D.R., 2006. Metabolic Bone Disorders – Reptile Medicine and Surgery. 2nd edition. Missouri: Elsevier.
  2. Klaphake, E., 2010. A fresh look at metabolic bone diseases in reptiles and amphibians. Veterinary Clinics of North America: Exotic Animal Practice, 13(3), 375–392.
  3. Antwis, R.E., Browne, R.K., 2009. Ultraviolet radiation and vitamin D-3 in amphibian health, behaviour, diet and conservation. Comp Biochem Physiol A Mol Integr Physiol, 154(2), 184–90.
  4. Troyer, K., 1984. Diet selection and digestion in Iguana iguana, the importance of age and nutrient requirements. Oecologia
  5. 61, 201
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