Metabolic Bone Disease (MBD) in Reptiles

What Is Metabolic Bone Disease in Reptiles?

Metabolic bone disease, also known as nutritional secondary hyperparathyroidism, is one of the most common diseases of pet reptiles.

As the name implies, it’s a disease that affects the skeletal system, causing weak, rubbery, and easily broken bones. It also causes abnormal muscle twitching or movement.

Metabolic bone disease (MBD) occurs if a pet reptile has abnormal calcium, phosphorus, and vitamin D3 levels, either caused by a poor diet or poor care. Fast-growing or reproducing animals are the most susceptible, but all reptiles will succumb to MBD if not provided with the correct environment.

MBD in reptiles can take months to develop and leads to death if left untreated. While reptiles are common pets, they have not adapted to living in domestic environments and have species-specific needs. Therefore, they require very particular temperatures, humidity, and supplements within their aquarium or terrarium.

Veterinarians diagnose MBD most often in lizards, turtles, and tortoises, but can also be found in amphibians and snakes.

If you suspect your reptile may be suffering from MBD, contact your veterinarian immediately.

Symptoms of Metabolic Bone Disease in Reptiles

Decreased appetite, lethargy, and weight loss are often the first signs of metabolic bone disease in reptiles. As the disease progresses, other signs may include:

• Broken bones

• Rubbery legs

• Swollen jaw or legs

• Misshapen or soft shell (in turtles and tortoises)

• Inability to walk or move normally

• Muscle twitches

• Rigid muscles

• Inability to urinate/defecate

• Cloacal prolapse—internal tissues protrude from the cloaca (the common opening for urinary, reproductive, and intestinal systems)

• Seizures

• Death

Causes of Metabolic Bone Disease in Reptiles

Reptiles require their terrarium or aquarium to replicate their natural habitat. When a reptile does not have enough calcium provided (either by not ingesting it or being unable to absorb it), they will begin to take calcium from their bones, leading to brittle, frail bones that break easily.

Calcium is essential for multiple functions in the reptile’s body, including:

• The nervous system

• Muscle contractions

• Clotting functions

• The gastrointestinal system

• The immune system

• The endocrine system

• The reproductive system

Pet reptile diets are notorious for having incorrect amounts and ratios of vitamins and minerals. Because of this, reptiles in captivity require multiple supplements to keep them healthy. If fed a calcium-poor diet or an incorrect ratio of calcium to phosphorus, the body begins to remove calcium from the skeletal system.

Reptiles also require ultraviolet light (UVB) to metabolize vitamin D3, which in turn regulates calcium and phosphorus. When reptiles are not provided the proper temperature, humidity, and UVB, they cannot metabolize vitamin D3 or absorb calcium appropriately.

Risk Factors for Metabolic Bone Disease in Reptiles
All reptiles are vulnerable to MBD; however, some are at higher risk. If you have a reptile that is considered high-risk, consult with an exotic veterinarian to determine what their diet and care should look like. 

Remember, all reptile species can acquire MBD, but the most commonly diagnosed reptiles include:

• Sulcata tortoises

• Leopard tortoises

• Bearded dragons

• Water dragons

• Iguanas

• Leopard geckos

• Chameleons

Reptiles that eat whole prey items, such as snakes, may be less likely to develop MBD due to higher calcium levels in their diet.

Additional risk factors for MBD include:

• Young animals who are still growing and have higher calcium demands than adults

• Egg-laying or reproducing animals

• Stress, which can alter calcium resorption

• Poor diet

• Parasites

• Lack of calcium supplementation

• Lack of UVB lighting

• Lack of proper temperature and humidity

How Veterinarians Diagnose Metabolic Bone Disease in Reptiles

Veterinarians suspect metabolic bone disease based on the physical exam and husbandry evaluation alone. However, radiographs and blood work are crucial for an official diagnosis and treatment monitoring.

Radiographs, or X-rays, are often used to evaluate bone health. As MBD progresses, the reptile’s body will remove calcium from the skeleton, leaving thin, de-mineralized bones. Radiographs also evaluate the skeletal system for any abnormal bony lumps or fractures to treat as needed.

Blood work, such as a complete blood count and blood chemistry profile, will often show:

• Low ionized calcium

• High phosphorus

• Low vitamin D3

Fecal samples are useful for determining gastrointestinal parasites that may alter the reptile’s ability to absorb nutrients.

Treatment of Metabolic Bone Disease in Reptiles

The immediate goals of treatment are to stop life-threatening symptoms, including:

• Seizures

• Dehydration

• Cloacal prolapse

• Fractures

Once these life-threatening conditions are addressed, veterinarians will work to restore calcium, phosphorus, and vitamin D3 levels to normal. Correction of diet and care is critical to treatment. Depending on the severity of signs, your veterinarian may recommend one or more of the following treatments:  

• Oral or injectable calcium

• Fluid therapy

• Ultraviolet light therapy

• Phosphate binders

• Oral/injectable vitamin D

• Dewormers

• Food support—may require hand-feeding

• Pain management

Metabolic bone disease can be fatal in reptiles. If a pet parent suspects MBD, they should seek veterinary care immediately. While correcting reptile care is crucial to reversing MBD, there are no home remedies to correct MBD once it has started. Pet parents should work closely with an exotic veterinarian for the best possible outcome.

Recovery and Management of Metabolic Bone Disease in Reptiles

The recovery timeline for metabolic bone disease in reptiles varies based on the severity of the disease.

Reptiles with severe MBD may take months to recover, and many succumb to the disease during the treatment process. Reptiles often hide their illness until it has progressed significantly, and humane euthanasia may be an option for severe cases.

During the recovery process, make sure to remove all other animals from the pet’s enclosure to decrease stress or physical injury. Reptiles with MBD should not be allowed to climb–they are at risk of falling and further injuring themselves.

Pet parents should handle reptiles with MBD with extreme care, as their bones are fragile. Work with your veterinarian to determine the best way to handle your pet safely, especially if hand-feeding, until they eat independently.

Veterinarians may recommend increased soaking or baths. Always monitor the water level—never allowing it to go above the reptile’s shoulders. Reptiles in a weakened state may not be able to hold their head above water and require constant monitoring when bathing to prevent accidental drowning.

Pet parents should also provide plenty of hiding places as sick animals often feel more secure when hidden. 

Prevention of Metabolic Bone Disease in Reptiles

Providing proper care is the best prevention of metabolic bone disease in reptiles.

Always keep detailed journals of your reptile including daily habits to monitor for changes. Take note of:

• Thermometers

• Hygrometers

• UV meters

• Infrared heat detectors

• Weight

• Bowel movements

• Dates light bulbs are changed

• Shedding cycles

• Appetite

Use caution when feeding your reptile calcium-rich foods. While reptiles absolutely require calcium in their diet, too much calcium can also cause issues. Hypercalcemia, or high blood calcium levels, can cause:

• Heart conditions

• High blood pressure

• Bone defects

• Kidney failure

It is important to provide the correct amount of calcium for your reptile.

Always check with your veterinarian regarding reptile supplements, especially which products should include D3. This will vary from species to species, as well as the individual home environment and enclosure. Some common veterinarian-approved products include:

• Repashy Superfoods Calcium Plus

• Repti Calcium (without D3)

• Repti Calcium (with D3)

• Reptivite (without D3)

• Reptivite (with D3)