Austwickia chelonae - New Information & What to do if you see it

[turtlesteve]

OK guys. During the past year I have observed/treated tortoises with Austwickia and documented the results. I have also discussed this disease with several veterinarians at this point and it's time for a data dump.

General information on the disease:

1. The "yellow bump" disease is caused by the bacterium Austwickia chelonae. It was renamed from Dermatophilus, and most vets are only familiar with this older name in the context of a closely related bacterium that affects mammals. The first symptom of infection is lack of growth, followed by yellow skin lesions. In bad cases, toenails and jaw sheaths become necrotic and fall off. Once symptomatic it is near 100% fatal without treatment.

2. It can be killed with ammonia-based disinfectants (we already knew this much). However it is quite difficult to fully eradicate, it will probably live in soils for quite some time (or indefinitely?) and thus creates the potential to hide somewhere and become infectious later. It is suspected that tortoises can be asymptomatic carriers, and visible cases in adult tortoises seem to be very rare.

3. It is everywhere. Large breeders, retailers, etc. across the country. A wild gopher tortoise in Florida. Wild crocodile lizards in China. We are past the point of being able to contain this, and so all captive bred hatchlings should be considered at risk of becoming sick, no matter where you obtain them. Once they are older (a year?) the risk is probably much less.

4. It is probably an opportunistic pathogen. From what we know, it wants wet conditions near 80F. It can survive in other conditions but may not grow or be infectious (we are not entirely sure). It is probable that exposed hatchlings will develop the disease, or not, depending on environment and possibly the strength of their immune system. I do fear a catch-22 that better husbandry may inadvertently increase risk given that the disease prefers high humidity. It seems probable that all species are susceptible, but this is not confirmed. I have not seen evidence of a case in star tortoises yet, for example.

5. I have some suspicion that it transmits vertically (mother to babies) via contamination of eggshells, but there is no hard evidence at this time.

Treatment:

1. If the tortoise is acting and eating normally, and has only skin lesions, there is a good chance it can be saved. A sensitivity study (below) performed by researchers in China confirmed that Austwickia is susceptible to antibiotics. The most useful finding is that penicillin-group antibiotics are effective. Ampicillin was used in the study, but would require regular injections for a long period of time (not a great idea for hatchling tortoises). I used amoxicillin (which is better absorbed when given orally than other penicillin antibiotics). My procedure was 100 mg/kg amoxicillin per day given orally. Tablets can be crushed, mixed with calcium supplement powder, and the appropriate dose can be dusted onto food each day. The disease is also susceptible to minocycline (and therefore likely tetracycline). I mention this because tetracycline is easy to find and may have been key to saving shawnateerow's sulcatas.


Reference: Jiang, H. et al. Identification of Austwickia chelonae as cause of cutaneous granuloma in endangered crocodile lizards using metataxonomics. PeerJ 2019 7:e6574

2. Treatment may require 3-4 months of antibiotics. I did not stop until all the skin bumps shed off and they started growing. During treatment the tortoise habitat should be made less hospitable for the pathogen. Complete disposal of existing substrate and swap to something that will not retain moisture. Dry conditions are not great for baby tortoises, but they can be kept hydrated by soaking / drinking. Do not worry about pyramiding at this time, it will only affect growing tortoises and they will not grow until they recover from the disease.

3. It might be useful to have a big temperature swing (day to night) if the tortoise species can tolerate it. This is purely speculative but if the bacteria prefer temperatures near 80F, we can deny them that satisfaction for at least some portion of the day.

 

[zovick]

OK guys. During the past year I have observed/treated tortoises with Austwickia and documented the results. I have also discussed this disease with several veterinarians at this point and it's time for a data dump.

General information on the disease:

1. The "yellow bump" disease is caused by the bacterium Austwickia chelonae. It was renamed from Dermatophilus, and most vets are only familiar with this older name in the context of a closely related bacterium that affects mammals. The first symptom of infection is lack of growth, followed by yellow skin lesions. In bad cases, toenails and jaw sheaths become necrotic and fall off. Once symptomatic it is near 100% fatal without treatment.

2. It can be killed with ammonia-based disinfectants (we already knew this much). However it is quite difficult to fully eradicate, it will probably live in soils for quite some time (or indefinitely?) and thus creates the potential to hide somewhere and become infectious later. It is suspected that tortoises can be asymptomatic carriers, and visible cases in adult tortoises seem to be very rare.

3. It is everywhere. Large breeders, retailers, etc. across the country. A wild gopher tortoise in Florida. Wild crocodile lizards in China. We are past the point of being able to contain this, and so all captive bred hatchlings should be considered at risk of becoming sick, no matter where you obtain them. Once they are older (a year?) the risk is probably much less.

4. It is probably an opportunistic pathogen. From what we know, it wants wet conditions near 80F. It can survive in other conditions but may not grow or be infectious (we are not entirely sure). It is probable that exposed hatchlings will develop the disease, or not, depending on environment and possibly the strength of their immune system. I do fear a catch-22 that better husbandry may inadvertently increase risk given that the disease prefers high humidity. It seems probable that all species are susceptible, but this is not confirmed. I have not seen evidence of a case in star tortoises yet, for example.

5. I have some suspicion that it transmits vertically (mother to babies) via contamination of eggshells, but there is no hard evidence at this time.

Treatment:

1. If the tortoise is acting and eating normally, and has only skin lesions, there is a good chance it can be saved. A sensitivity study (below) performed by researchers in China confirmed that Austwickia is susceptible to antibiotics. The most useful finding is that penicillin-group antibiotics are effective. Ampicillin was used in the study, but would require regular injections for a long period of time (not a great idea for hatchling tortoises). I used amoxicillin (which is better absorbed when given orally than other penicillin antibiotics). My procedure was 100 mg/kg amoxicillin per day given orally. Tablets can be crushed, mixed with calcium supplement powder, and the appropriate dose can be dusted onto food each day. The disease is also susceptible to minocycline (and therefore likely tetracycline). I mention this because tetracycline is easy to find and may have been key to saving shawnateerow's sulcatas.

View attachment 359800
Reference: Jiang, H. et al. Identification of Austwickia chelonae as cause of cutaneous granuloma in endangered crocodile lizards using metataxonomics. PeerJ 2019 7:e6574

2. Treatment may require 3-4 months of antibiotics. I did not stop until all the skin bumps shed off and they started growing. During treatment the tortoise habitat should be made less hospitable for the pathogen. Complete disposal of existing substrate and swap to something that will not retain moisture. Dry conditions are not great for baby tortoises, but they can be kept hydrated by soaking / drinking. Do not worry about pyramiding at this time, it will only affect growing tortoises and they will not grow until they recover from the disease.

3. It might be useful to have a big temperature swing (day to night) if the tortoise species can tolerate it. This is purely speculative but if the bacteria prefer temperatures near 80F, we can deny them that satisfaction for at least some portion of the day.

Very good information, Steve. Hopefully it will help other owners and save a large number of young tortoises.

 

[turtlesteve]

Outcome: 6 out of 7 clutch mates still alive. Growth rate is normal after recovery, but they basically did not grow at all for the first 6 months.

Leopard tortoise that passed in 2022. Note lots of lesions on the neck.


Clutch mates with fewer lesions. They all have 1-2 lesions at the time of the photo and new lesions would appear every few days.


Just before treatment was stopped. Notice this tortoise is the same as the upper right in the above image. There are still a couple of lesions on the neck but they are small and hard. They are gradually shedding off at this point.


About 4 months after the last picture. The tortoise is the uppermost one in this photo.

 

[Tom]

Great info. Thank you for posting all of this and sharing your experience.

 

[jsheffield]

Great Information!

Thanks for sharing your knowledge and experience.

Jamie

 

[dd33]

@turtlesteve I don't know much about the testing procedure for this. Can it be detected in the tortoise outside of a direct sample of the bumps? Have you done any follow up testing to see if you cleared the disease or just the symptoms? Assuming you have other tortoises in your collection, how have you kept this from spreading to them?

 

[turtlesteve]

@turtlesteve I don't know much about the testing procedure for this. Can it be detected in the tortoise outside of a direct sample of the bumps? Have you done any follow up testing to see if you cleared the disease or just the symptoms? Assuming you have other tortoises in your collection, how have you kept this from spreading to them?

1. I am told by UF that it can be confirmed by PCR testing of a tissue sample from the bumps themselves. I do not know if it could be tested on cloacal swabs but I will ask.

2. I have not attempted follow up testing yet. My concern will be accuracy, other diseases like TINC can be present and not show up on tests. So essentially you can never 100% trust a negative result.

3. I am using aggressive biosecurity procedures and keeping groups of animals isolated from each other. The leopards are kept in a different building by themselves. Also, all other fatalities (two) over the past year were sent off for necropsy and Austwickia was not present.

 

[Tim Carlisle]

Following.

 

[Tim Carlisle]

@turtlesteve I'd be curious to know the effectiveness of treatment when symptoms first appear vs. the point at where the lesions are wider spread. I assume it's better to treat as early as possible, but is there a defined timeline of effectiveness as the disease progresses?

 

[jsheffield]

OK guys. During the past year I have observed/treated tortoises with Austwickia and documented the results. I have also discussed this disease with several veterinarians at this point and it's time for a data dump.

General information on the disease:

1. The "yellow bump" disease is caused by the bacterium Austwickia chelonae. It was renamed from Dermatophilus, and most vets are only familiar with this older name in the context of a closely related bacterium that affects mammals. The first symptom of infection is lack of growth, followed by yellow skin lesions. In bad cases, toenails and jaw sheaths become necrotic and fall off. Once symptomatic it is near 100% fatal without treatment.

2. It can be killed with ammonia-based disinfectants (we already knew this much). However it is quite difficult to fully eradicate, it will probably live in soils for quite some time (or indefinitely?) and thus creates the potential to hide somewhere and become infectious later. It is suspected that tortoises can be asymptomatic carriers, and visible cases in adult tortoises seem to be very rare.

3. It is everywhere. Large breeders, retailers, etc. across the country. A wild gopher tortoise in Florida. Wild crocodile lizards in China. We are past the point of being able to contain this, and so all captive bred hatchlings should be considered at risk of becoming sick, no matter where you obtain them. Once they are older (a year?) the risk is probably much less.

4. It is probably an opportunistic pathogen. From what we know, it wants wet conditions near 80F. It can survive in other conditions but may not grow or be infectious (we are not entirely sure). It is probable that exposed hatchlings will develop the disease, or not, depending on environment and possibly the strength of their immune system. I do fear a catch-22 that better husbandry may inadvertently increase risk given that the disease prefers high humidity. It seems probable that all species are susceptible, but this is not confirmed. I have not seen evidence of a case in star tortoises yet, for example.

5. I have some suspicion that it transmits vertically (mother to babies) via contamination of eggshells, but there is no hard evidence at this time.

Treatment:

1. If the tortoise is acting and eating normally, and has only skin lesions, there is a good chance it can be saved. A sensitivity study (below) performed by researchers in China confirmed that Austwickia is susceptible to antibiotics. The most useful finding is that penicillin-group antibiotics are effective. Ampicillin was used in the study, but would require regular injections for a long period of time (not a great idea for hatchling tortoises). I used amoxicillin (which is better absorbed when given orally than other penicillin antibiotics). My procedure was 100 mg/kg amoxicillin per day given orally. Tablets can be crushed, mixed with calcium supplement powder, and the appropriate dose can be dusted onto food each day. The disease is also susceptible to minocycline (and therefore likely tetracycline). I mention this because tetracycline is easy to find and may have been key to saving shawnateerow's sulcatas.

View attachment 359800
Reference: Jiang, H. et al. Identification of Austwickia chelonae as cause of cutaneous granuloma in endangered crocodile lizards using metataxonomics. PeerJ 2019 7:e6574

2. Treatment may require 3-4 months of antibiotics. I did not stop until all the skin bumps shed off and they started growing. During treatment the tortoise habitat should be made less hospitable for the pathogen. Complete disposal of existing substrate and swap to something that will not retain moisture. Dry conditions are not great for baby tortoises, but they can be kept hydrated by soaking / drinking. Do not worry about pyramiding at this time, it will only affect growing tortoises and they will not grow until they recover from the disease.

3. It might be useful to have a big temperature swing (day to night) if the tortoise species can tolerate it. This is purely speculative but if the bacteria prefer temperatures near 80F, we can deny them that satisfaction for at least some portion of the day.

I'd read a few articles on AC that mentioned debridement of the lesions... has that been part of your treatment regimen, or are antibiotics and temp/humidity modification the mainstays?

Thanks,

Jamie

 

[turtlesteve]

@turtlesteve I'd be curious to know the effectiveness of treatment when symptoms first appear vs. the point at where the lesions are wider spread. I assume it's better to treat as early as possible, but is there a defined timeline of effectiveness as the disease progresses?

We need to have more cases documented to know for sure, but I believe the effectiveness of treatment and speed of recovery will increase if caught early.

Times I’ve talked to someone about a case, they didn’t respond or the tortoises died already. One person I know that buys and resells got hit twice in one year from different sources, but the tortoises had died by the time I heard of it.

I'd read a few articles on AC that mentioned debridement of the lesions... has that been part of your treatment regimen, or are antibiotics and temp/humidity modification the mainstays?

Thanks,

Jamie

I have not done very much in this regard. The main threat of the disease seems to be the systemic / internal infection. I did find that silver sulfadiazine cream seems to help individual lesions, and I would expect every little bit helps in bad cases.

Some other thoughts:

1. The appearance of obvious skin lesions is not immediate and is not the first symptom. Infected tortoises exhibit no growth or slow, ugly, pyramided growth for some time (likely weeks to months) prior to lesions appearing. I question if there are cases where skin lesions never appear.

2. I have heard claims that this disease is not a big deal, only affects tortoises kept in unclean cages, etc. This is mostly BS. The only nugget of truth I see is that unclean cages may increase risk if it means allowing substrate to be wet.

3. Breeders selling hatchlings at 30-60 days old or less may not see hatchlings fall ill, so could be oblivious. That being said my gut tells me most affected breeders know and are unwilling to admit it and/or talk about it.

 

[dd33]

I think this thread might get some peoples hopes up a bit too much and provide cover for unscrupulous breeders selling animals with this disease. Sellers will no doubt refer to this and say there is a cure now, don't worry about it. @turtlesteve let me know if you disagree.

Clearing these animals of the visible symptoms of the disease does not mean that the disease is gone. It might come back next week, it might come back 5 years from now. It may never come back. Is it going to be transmitted to other tortoises while asymptomatic? That is likely the case since adult animals don't seem to be impacted by this disease the way hatchlings are.

I have a different incurable and lethal disease in my Radiateds. The seller told me they don't have that disease in their Radiateds but they do have it in another species in their collection. I was told to use a medication to clear it up that has little chance of doing anything other than clearing the symptoms. UF vets said the medication will not cure them, it is fatal and to euthanize anything that has come in contact. I am a skeptic when given medical advice by anyone that sells animals, even if they are a vet.

 

[turtlesteve]

I think this thread might get some peoples hopes up a bit too much and provide cover for unscrupulous breeders selling animals with this disease. Sellers will no doubt refer to this and say there is a cure now, don't worry about it. @turtlesteve let me know if you disagree.

I don’t disagree, but the thing is, unscrupulous sellers are already selling animals with it. This has been circulating very widely for at least 3-4 years now and probably longer. If they are making that choice, it will be so regardless of whether there is a treatment. They’re counting on people being uninformed.

Clearing these animals of the visible symptoms of the disease does not mean that the disease is gone. It might come back next week, it might come back 5 years from now. It may never come back. Is it going to be transmitted to other tortoises while asymptomatic? That is likely the case since adult animals don't seem to be impacted by this disease the way hatchlings are.

We just don’t know enough yet. Given the rarity of symptomatic cases in adults I suspect they do develop some immunity. My hope is that quarantine works and we can prevent transmission to hatchlings or modify husbandry so that it doesn’t become infectious.

The mammalian versions of this disease are generally not transmitted animal to animal (they get it from the environment). This disease by contrast does APPEAR to transmit animal to animal (as all hatchlings in my group showed symptoms) but it may be because the sick animal contaminated the substrate.

I have a different incurable and lethal disease in my Radiateds. The seller told me they don't have that disease in their Radiateds but they do have it in another species in their collection. I was told to use a medication to clear it up that has little chance of doing anything other than clearing the symptoms. UF vets said the medication will not cure them, it is fatal and to euthanize anything that has come in contact. I am a skeptic when given medical advice by anyone that sells animals, even if they are a vet.

I share your disappointment here, in terms of the ethics of the situation.

From a pragmatic standpoint I see little choice but to attempt to treat and manage diseases like this. Euthanizing infected animals may be appealing in the short term and may have merit if the disease is not widespread. In the long term collective sense it’s a disaster — it’s not going to stop the spread of these diseases, and it’s just not a tenable solution when these diseases hit turtles and tortoises that are critical for conservation.