Shell Rot

Shell Rot

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How To Prevent & Treat Shell Rot

Shell Rot also known as ulcerative shell disease is a common yet serious condition that can easily be prevented with proper husbandry.

Notwithstanding, the misconceptions about it are numerous and persistent. Perhaps most concerning, there is a widespread myth that shell rot only affects aquatic turtles.

Quick Reference Section

Let me disabuse of this one first – shell rot is common in tortoise genera around the world, including Testudo, Chelonoidis, Centrochelys and Stigmochelys, whose species we commonly keep as pets.

Another misconception is that shell rot is only caused by bacteria. Again, let’s not be drawn in by folklore! Although scientific evidence suggests that most cases are caused by bacteria, a significant percentage are instead caused by fungi – while yet, others involve both.

The initial infection can stem from poor hygiene, lack of a dry area, or an injury; meaning errors in husbandry can allow shell rot to take hold in previously healthy animals.

Bearing this in mind, it is important to get an understanding of the condition so it can be dealt with correctly.

In this article, we’re going look at how to identify shell rot, how to distinguish it from healthy scute shedding, and how to treat it.

What does shell rot look like?

Hermanns Tortoise with shell rot
Hermann’ tortoise with shell rot

In aquatic turtles, shell rot commonly appears as whitish or grey spots. Over several months, the lesions spread outwards across the shell and inwards towards the underlying bone, leading to raised, flaking scutes and mushy areas.

Another sign of shell rot in aquatic turtles is an unusual dent, hole or pitting that appears on an otherwise smooth patch of shell. Occasionally, it appears as angry red or orange ulcers that spread quickly.

This type of shell rot is less common, but on the one occasion where I have seen it, Staphylococcus bacteria were found to be the cause.

Algae can be a contributing factor in shell rot, but in adult Musk Turtles (Sternotherus spp.) algal growth on the shell is common and generally harmless.

In tortoises and terrestrial turtles, shell rot often starts on the plastron – a good reason to regularly lift your tortoise up (without turning him/her upside down) and have a look at shell condition.

Though it does take on a whitish or orange appearance, it can be obscured by dirt and go undetected for some time. Sometimes starting in the cracks between scutes before spreading outwards across them, it also presents as round lesions.

In some cases, it causes a thickening and flaking of the scutes, producing a puff pastry effect. This last detail is a tell-tale sign of an advanced infection.

In both aquatic turtles and terrestrial turtles and tortoises, shell rot eventually causes deep ulcers and soft, rotten depressions in the shell, making it unmistakable.

Sometimes, whole scutes fall off, which can be distressing to see. Before this point, smell can be good clue that the disease is present.

A smell of mouldy old gym socks or stagnant water can be quite strong when the lesions are gently roughed up with a scraper.

Does my turtle have shell rot, or is it shedding?

Shell_rot_in_red eared slider
Red ear slider with shell rot

Scute shedding is a natural occurrence for most species of aquatic turtle, being observed frequently in juveniles and annually or biannually in adults.

That said, it can be hard to tell the difference between healthy shedding, called ecdysis, and unhealthy shedding, called dysecdysis (think dysfunctional).

Ecdysis occurs because the outer layers of turtle scutes are made of keratin and must be shed for new, larger ones to replace them in line with your turtle’s growth.

Dysecdysis occurs when an animal is sick, overfed, injured, or exposed to a basking light that is too hot.

How can I tell between ecdysis and dysecdysis?

1. Tortoises and terrestrial turtles do not shed scutes unless shell rot or an injury is present.

2. Softshell turtles never shed scutes (they don’t have any!).

3. Diamondback Terrapins only shed scutes once they get to approximately 5-6 inches (12.5 – 15 cm) in carapace length (measured by placing a ruler on the midline of the carapace and viewing it from above).

4. Healthy scute shedding is one layer at a time, separated by weeks or months – not a continuous process.

5. Layers that come off during healthy shedding are paper thin and sometimes see through.

6. Healthy shedding means all the carapace and plastron at the same time – not just one scute.

7. During healthy shedding, scutes come off whole.

8. Scutes that are shedding often get air trapped under them and look reflective when underwater.

9. White bone is never exposed after healthy shedding.

Ecdysis is a good sign – it allows the shell to grow and makes it look brand new. The process can take 5-6 weeks for an adult, or considerably less time for a juvenile.

A dry basking spot and unfiltered UVB light aid the process, with many keepers noticing that turtles kept outdoors in warm climates shed more quickly.

Some turtle specialists recommend supplementing with Koi pellets containing wheat germ during shedding (around once a week), as they are high in Vitamin E which promotes skin and shell health.

Dysecdysis can be a sign of shell rot if other causes have been ruled out.

How to treat shell rot and when to see a vet

How to treat shell rot varies depending on its severity. Let’s put it into two categories based on this: early stage and late stage/acute shell rot.

Early stage shell rot appears as white or discoloured patches, and/or slight dysecdysis. It can be managed at home if you carry out treatment daily and keep a photo log of progress.

Before starting, be sure to double check enclosure temperatures – reptiles never recover well if their temperatures are off!

For early stage shell rot in aquatic turtles follow these steps:

  1. Scrub the area gently with a toothbrush and lukewarm water to remove any dirt. Let the shell dry.
  2. Apply either povidone-iodine or silver sulfadiazine ointment to the affected area. Let dry for an hour before returning the turtle to its enclosure.
  3. Repeat daily for three weeks.
  4. Change out the water regularly and change your pump filter at the start of treatment.

Remember, aquatic turtles need a basking area that allows them to dry off completely. Turtle docks that sink when the turtle climbs on are no good! If your turtle cannot regularly get completely dry, then treatment will not work.

For early stage shell rot in tortoises follow the same steps, but also try to lower humidity in the enclosure. This will help slow microbial growth.
Improvement should be noticeable within two to three weeks. If not, consult a reptile vet as soon as possible.

Though many keepers recommend using hydrogen peroxide to treat shell rot, there are concerns that it slows healing in healthy tissue. My advice would be to stick to the two antiseptics I mention above.

Late stage/acute shell rot

Late stage/acute shell rot is characterised by dents, mushy white or red areas and/or severe dysecdysis. At this stage, the condition is much more serious and will need to be managed by a reptile vet. Pain management and systemic treatments are usually necessary.

If you take a turtle or tortoise with acute shell rot to a reptile vet, they will start by assessing the animal and possibly administering pain medication.

After this, they may decide that debridement of some infected areas is necessary under anaesthesia. Debridement, the surgical removal of dead tissue, can dramatically improve the results of treatment.

At the same time, a tissue sample for microbial culture may be taken which will determine what pathogen is involved. If bacteria are involved, then the results of the culture will be definitive within a few days.

Do not be surprised if your vet begins treatment with antifungal or antibacterial medication before the results of the culture are back, or without taking a sample. In severe cases it is better to get a head start using broad-spectrum medication.

Treatment works, but prevention is better!

The treatments described above are usually successful, but it is essential that you determine why your pet got shell rot in the first place!

If an injury was involved, this should tell you that your animal’s enclosure is not safe enough, and probably not hygienic enough either.

Tortoise shell rot often starts from dirty or damp substrate because their plastrons are constantly in contact with it. It is important to maintain the hygiene of a tortoise enclosure by quickly removing old food or faeces and replacing substrate regularly.

Particular attention is advised if you hibernate your tortoise because their immune system does not function efficiently during this time.

Personally, I do not recommend hibernating tortoises outdoors, as a controlled setting in your garage is safer and more hygienic.

In aquatic turtles, shell rot is commonly caused by poor water hygiene.

Keeping a tank full of water clean – with an animal eating and defecating in it – can be a challenge!

Once you start looking into it, however, there is an incredible range of products made for precisely this purpose.

Water filters with built-in UV sterilisers, for example, can dramatically improve water hygiene.

Wrapping up

Using this article, you should be able to determine if your animal has shell rot, what to do about it, and whether you need to consult a vet.

Fortunately, shell rot is highly treatable and can usually be cured in a matter of weeks. More to the point, if you put in the time and do the research, you can prevent it from coming back.

If your animal has suffered with shell rot, make sure it gets the treatment it needs, then use this website to review your husbandry and banish the disease for good!

About the author

    Will Bruce

    Will Bruce is a herpetologist whose passion is educating people about reptiles and amphibians. With over 20 years of experience, he has contributed to publications that focus on Ball Pythons, herpetoculture, field herpetology and south-east Asian ecology. These days, he splits his time between running his educational website - Ballpythonbreeder.co.uk, breeding Ball Pythons and going on herping trips abroad.

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