Common Turtle Shell Diseases 101

What are the most common types of shell disease in turtles?

What are the symptoms of shell diseases?

Understanding turtle shell diseases and their symptoms are essential to the proper care of your turtle.

Knowing what to look for is key to getting your turtle prompt treatment before too much shell damage occurs.

If the proper diagnostic testing and treatment are not done, the shell disease will become very serious and possibly fatal.

In this article, we will take an in-depth look at turtle shell diseases and what causes them and how to possibly prevent them.

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What Are The Most Common Turtle Shell Diseases?

The most common turtle shell diseases include metabolic bone disease, shell rot, pyramiding, salmonella, and Dysecdysis. Many varieties of shell fungus also cause shell diseases, and in recent years, a new shell disease was discovered in the form of a shell-eating fungus found on freshwater turtles in the United States.

Most turtle shell diseases are caused by poor diet and unclean living conditions, making these diseases easily preventable.

Here, we will give you a brief overview of the most common turtle shell diseases, including their symptoms, so you will know what to look out for in your pet turtle.

Metabolic Bone Disease (MBD)

Metabolic Bone Disease occurs when a turtle is deficient in calcium or vitamin D.

In the form of D3, Vitamin D is essential for a turtle to absorb calcium in its body properly.

Vitamin D3 may be given as a supplement powder or synthesized from vitamin D absorbed by the turtle through ultraviolet light.

It is strongly suggested to give your turtle a D3 supplement if it is not exposed to adequate UVB light during the day to avoid a calcium deficiency.

Calcium supplements are available both with and without D3.

Too much phosphorus in a turtle’s diet will also disrupt calcium absorption in the turtle’s body, so be sure to choose supplements without it.

The early stages of metabolic bone disease begin when the turtle’s body starts leaching calcium from its bones to make up for the calcium deficiency.

As the disease progresses, the turtle’s shell will appear deformed and may even become soft.

Other symptoms of metabolic bone disease include a deformed jaw and deformed or weak limbs.

In severe cases of the disease, the spine is affected, and paralysis will occur. 

If your pet is experiencing soft shell we recommend reading our post on treating turtle soft shell.

Shell Rot

Shell rot is an infection caused by bacteria and fungus found in dirty water or an unclean habitat.

This bacteria and fungus infect the turtle through cracks or punctures in the shell caused by aggressive fighting or improper humidity and temperature.

Sharp objects within your turtle’s enclosure also pose a risk of damaging the shell when the turtle crawls over them.

Aquatic turtles are susceptible to getting shell rot through dirty water and not having an area to dry out.

Your aquatic turtle needs an area of land where it can dry off completely.

This not only prevents excessive overgrowth of bacteria or fungus but also aids in the shedding process.

Symptoms of shell rot are:

  • An uneven shell.
  • Small white pits in the shell’s surface.
  • A foul-smelling reddish discharge.
  • Peeling scutes.

When these scutes fall off of the carapace, the bone underneath becomes exposed.

In severe shell rot cases, the infection gets into the bloodstream and causes a form of sepsis known as Septicemic Cutaneous Ulcerative Disease, or SCUD.

SCUD is a very serious form of shell rot, and it is often fatal if proper treatment is not sought immediately.

Treatment usually consists of injectable antibiotics and fluid therapy to prevent dehydration.


Pyramid is often a side effect of metabolic bone disease caused by a calcium deficiency, but it is also caused by low fiber or excessive protein in the turtle’s diet.

Signs of pyramiding include shell deformities where the scutes on the carapace grow irregularly.

This irregular growth leads to the scutes forming in a raised conical shape, resembling tiny pyramids on the shell.

Pyramiding is not reversible, but if the underlying cause is treated, the new shell growth will be smooth and flat.

If you notice signs of pyramiding on your pet turtle’s shell, you should seek the care of a veterinarian as soon as possible to determine the root cause.

Since pyramiding is often caused by metabolic bone disease, you will also need to evaluate your turtle’s diet for any vitamin or mineral deficiencies such as vitamin D3 or calcium. 

If pyramiding is left untreated, it will become fatal to your turtle.

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Salmonella is a bacteria commonly found in an animal’s digestive tract and passed through its feces.

Turtles, however, carry the salmonella bacteria on their skin and shells.

In animals and people who are susceptible to the disease, salmonella germs cause severe stomach issues.

These stomach symptoms range from abdominal pain and cramping, fever, nausea, vomiting, and diarrhea.

Very serious cases of salmonella may even lead to a blood disease known as septicemia.

Small children, the elderly, and immunocompromised people have the highest risk of developing complications and severe disease, and they should limit their contact with turtles.

Most turtles who carry salmonella germs are asymptomatic, meaning they do not have any disease symptoms.

Salmonella is a zoonotic disease, which means it is easily passed from animals to humans.

There were even laws passed in the 1970s prohibiting turtle sale with a shell length smaller than 4″ inches (10 cm).

This legislation was meant to discourage small children from putting smaller turtles in their mouths and possibly contracting salmonella.

Some of these laws are still in place, so it is best to check with your local government involving pet turtles’ legal ownership.

Be sure to wash your hands thoroughly after handling or feeding your turtle, as well as after cleaning its enclosure.

Clean the feces from your turtle’s enclosure every day, and perform deep cleaning at least once a month.

It is also wise to wash your turtle’s items in a separate area from where you would wash items such as dishes or other human food utensils to avoid salmonella cross-contamination.


Dysecdysis is used to describe the condition where a scute is not shed properly.

This shell disease most commonly occurs in aquatic turtles, as most land-dwelling turtles retain their scutes for life, while aquatic turtles shed them.

This shedding process allows the aquatic turtle to prevent an overgrowth of bacteria or fungus on its shell.

In dysecdysis, the retained scutes may become infected, and you should seek treatment from a veterinarian as soon as you see any symptoms.

Abnormal shedding in aquatic turtles is typically caused by high ammonia levels in the water, fungal infections, overeating, and an overly hot enclosure or basking spot.

Many diseases of the bones, kidneys, liver, thyroid, and a calcium or vitamin D deficiency may also lead to shedding more than normal.

Dysecdysis is more likely to occur if your turtle does not have a land space to completely dry off or if it does not bask long enough for its old scutes to shed.

You should never pull a loose scute away from a turtle’s shell, as this greatly increases the chance of an infection or injury.

Turtle Shell Fungus

Shell fungus is more commonly associated with aquatic turtles, but land-dwelling turtles are also susceptible if their environment is too humid.

Poor water quality and habitat sanitation are the leading causes of fungus growth, so it is important to perform regular cleanings of your turtle’s enclosure.

Water filters greatly reduce the number of bacteria in an aquatic turtle tank. 

Keeping terrestrial turtles at the proper temperature and humidity will keep fungus from growing in their enclosure.

Green, fuzzy patches on the turtle’s shell are a sign of a fungus overgrowth, and they should not be confused with the white patches on a turtle associated with shedding.

If you see these green patches on your turtle’s shell or skin, you should bathe your turtle with mild soap and gently scrub the fungus away using a soft toothbrush.

Once the fungus can penetrate the shell’s surface, it will lead to infection and shell rot.

A turtle’s shell may crack from improper humidity or temperatures in its enclosure, or it may become damaged from sharp objects it has crawled over.

If two males are housed in the same enclosure, they will likely become aggressive towards each other, and this fighting will also cause damage to the turtle’s shell.

Once an infection such as shell rot has set in, it becomes very dangerous to your turtle and may even become fatal.

Shell-eating Fungus

As recently as 2011, researchers working through the Morris Animal Foundation discovered a fungus in freshwater turtles which was causing their shells to erode.

After taking samples from more than 70 freshwater turtles, including yellow mud turtles and the western pond turtle, these researchers were able to pinpoint a fungus named Endomyces testavorans.

This fungus gradually eats away at a turtle’s shell and moves through the reptile’s bones.

These open wounds make the turtle more susceptible to fungal and bacterial infection.

It remains unclear whether the fungus itself caused the lesions found on the freshwater turtle shells or if the shells had been previously damaged before the fungus set in.

Since the discovery of the fungus is so recent, scientists are also unsure if the fungus on its own is fatal to the turtle or if there are other underlying causes of death.

Researchers found the disease had done so much damage in the more severe cases they had to euthanize many wild turtles.

This shell-eating fungus in turtles is believed to be closely related to the types of fungus affecting other reptiles, such as snakes.

Researchers are uncertain if this fungal disease is new or has been present for a long time, and they simply just discovered it.

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What Are the Common Causes Of Turtle Shell Diseases?

The main culprit behind most of these common turtle shell diseases is poor nutrition.

Calcium and vitamin D3 deficiency make a turtle’s shell weak and more prone to infection by causing the shell to soften, crack, or become otherwise deformed.

An inappropriate diet will also lead to other diseases such as respiratory infections and gastrointestinal disease.

Poor temperature and humidity within a turtle’s enclosure will also lead to the shell becoming soft or cracking.

These cracks and deformities provide a gateway for a variety of bacteria and fungus to infect the turtle.

Unclean water and a poorly maintained, dirty habitat allow this fungus and bacteria to thrive.

When this bacteria and fungus are abundant within a turtle’s habitat, any type of trauma to the turtle’s shell becomes a dangerous breeding ground for infection.

There is no specific cause for salmonella being present on a turtle’s shell, as this is just a natural occurrence.

The salmonella germs a turtle carries on its skin and shell do not usually cause symptoms in the animal, but it may be dangerous to humans with compromised immune systems.

How Are Turtle Shell Diseases Prevented?

A lack of calcium or D3 directly causes many turtle shell diseases such as metabolic bone disease, shell rot, and pyramiding.

These common diseases are easily preventable by feeding your turtle a nutritious diet and providing it with calcium and vitamin supplements.

Placing a UV light, which emits UVB rays, within your turtle’s enclosure will also provide it with a way to synthesize vitamin D3.

Some calcium-rich foods include collard greens, cabbage, bok choy, alfalfa, spinach, okra, cantaloupe, squash, berries, and kale.

Avoid feeding your turtle iceberg lettuce, as it contains very few nutrients.

For omnivorous turtles, be sure to include a variety of live insects such as crickets, mealworms, silkworms, and small locusts which have been properly gut-loaded.

Vegetables and insects may be lightly dusted with a calcium or multivitamin supplement powder at every meal to ensure the turtle receives the right amount of nutrients.

This is an important step because calcium is vital to healthy shell growth. 

A turtle will not always get the right amount of calcium from their food regardless of whether it is herbivorous or omnivorous.

Proper habitat maintenance will also prevent many shell diseases caused by bacteria and fungus.

Regularly cleaning your turtle’s enclosure, adding a water filtration system to your aquatic turtle’s tank, and providing fresh, clean drinking water every day will go a long way to keeping harmful bacteria and fungus from growing.

While there is no prevention method for salmonella on a turtle’s shell, regularly bathing your turtle will prevent overgrowth of this and other bacteria as well as fungus.

To prevent becoming ill with salmonella, pet owners should limit their contact with turtles and thoroughly wash their hands after handling or feeding their turtles.

Final Thoughts

Learning to recognize the signs of turtle shell diseases will help you identify them more easily and seek treatment before becoming severe.

If left untreated, shell diseases will become fatal for your turtle.

Luckily, these turtle shell diseases are easily preventable by practicing good hygiene and providing your turtle with a well-rounded, nutritious diet.

Practicing a regular schedule of habitat maintenance and monitoring your turtle for any changes in appearance or behavior will prevent diseases and allow your turtle to grow a smooth and healthy shell.

If you notice any shell disease symptoms, you should seek veterinary care for your turtle right away for proper diagnostic testing and treatment.

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