Skip to main content

Yellow Fungus or Flesh Eating Fungus - Nannizziopsiosis in Bearded Dragons


Photo of clinical Nanizziopsiosis.  Note the yellow coloration of the infected area giving the disease its common name, yellow fungus.

Photo of clinical Nanizziopsiosis. Note the yellow coloration of the infected area giving the disease its common name, yellow fungus.

GMS with Hematoxylin counter stain of skin.  Black filaments (arrows) are fungal hyphae. Note the invasion of the alpha keratin layers of the stratum corneum. Red arrow = mass of fungal hyphae in interscalar space.

GMS with Hematoxylin counter stain of skin. Black filaments (arrows) are fungal hyphae. Note the invasion of the alpha keratin layers of the stratum corneum. Red arrow = mass of fungal hyphae in interscalar space.

Chrysosporium anamorph of Nannizziopsis vriesii

Nannizziopsiosis (Nan-eezee-opsee-osees or Nan-izi-opssee-osis where the first is the more correct Classical Latin pronunciation and the second is the Anglicized pronunciation) is a fungal disease of bearded dragons that has clinically been on the rise in recent years. I have seen at least 70 cases of this disease in the past year (2008) and only 20 cases the year before that. In 2006 I saw four cases of the disease. I did a presentation on the disease at one of the national pathology meetings in 2005, but the cases have been so common and questions so frequent of late, that I have decided to post this information.

The causative agent of the disease (called necrotizing mycotic dermatitis) is the Chrysosporium anamorph of Nannizziopsis vriesii. This fungus has been associated with fatal necrotizing dermatitis in crocodiles and with infections in numerous species of lizards. The same fungus that has been identified in numerous lizards (including identification through culture by a professional laboratory from cases I have seen) has even turned out to be potentially zoonotic. In 2005, Emerging Infectious Diseases volume 11, number 2, pages 349-350, reported brain abscesses in a human patient from this fungus. The patient was immunosuppressed due to HIV disease and had the fungus in the lungs as well as the brain.

In reptiles the disease is often called "yellow fungus." This is a poor and inexact name, since I have seen several cutaneous fungal infections (that were not this species) turn the skin yellow as it consumed the tissue. I therefore do not like to use the term. The correct disease name is necrotizing mycotic dermatitis (NMD) if the agent is not known. If the agent is known to be the Chrysosporium anamorph of Nannizziopsis vriesii, the correct etiologic diagnosis is Nannizziopsiosis. Nannizziopsis is the genus. According to the rules of naming a disease the terminus of the word is dropped and the suffix -osis or -iosis is added. Remember that the suffixes -asis, -iasis, -esis, -isis and -sis only mean that something is present. They do not mean that there is clinical disease.

STRANGE BUT TRUE SECTION: The rules of the suffixes is why dogs with heartworm disease do not have dirofilariasis. They have dirofilariosis. Dirofilariasis only means that heartworms are present, with or without clinical disease. Unfortunately, this is sometimes messed up even by primary care doctors because of erroneous usage and failure to distinguish between the two terms in Ettinger and Feldman's Textbook of Veterinary Internal Medicine which is extensively used by many veterinarians.

The fungus is a common soil fungus and is normally a saprophyte, that is a cleaner. It lives in the soil and digests the detritus and dead material and acts as a decomposer. However, whether there is a new strain or if the fungus is simply responding to a food source with no defenses is unclear. Yet, the fungus has been causing problems. I have generally noted that those farms growing lizards that are very healthy have few cases with Nannizziopsiosis. Most cases are sporadic and usually involve geriatric or highly stressed individuals. This observation gives credence to the hypothesis that the fungus is attacking a food source that has no defenses. Immunosupression may be the key to understanding the nature of the infection. Those poorly managed farms I have seen with high stress and poor management practices often have numerous cases of this disease. Combine that with the fact that once management improves the cases drop to a minimal level, again usually among the stressed or geriatric, then the pattern becomes more convincing.

Symptoms of Nannizziopsiosis

  1. Decreased appetite.

  2. Reluctance to move.

  3. Patchy yellowing of the skin followed by fragility of the yellow patches and/or dysecdysis.

  4. Yellow skin goes from thick and dry with adhered dead skin to moist and macerated in appearance, especially when upper layers of dead tissue are removed.

  5. Yellow areas begin to slough or turn brown or black and slough.

  6. Spread of the yellow and subsequent necrosis until the animal dies of secondary infections and/or shock.

Understanding the nature of the infection and the problems with topical antifungals is paramount to knowing how to treat the disease. The skin of most reptiles consists of several layers. The outermost layer is the dead layer called the stratum corneum or horny layer. The stratum corneum is made of several layers as well. The outermost is the oberhautchen and is compressed, waterproof beta keratin. The next layer is the beta layer, also waterproofing and made from beta keratin. The next layer is about 2-3 cell layers thick and is made from alpha keratin and is called the meso. The deepest layer of the statum corneum is the alpha layer, made of alpha keratin like a mammal's stratum corneum. Below the stratum corneum is the living layers of the skin consisting inconsistently of the stratum granulosum (this may be only one cell layer thick or largely absent in reptiles), and consistently of the stratum spinosum and stratum germinativum (stratum basale).

In brief here is an outline of the layers.

Stratum corneum

  1. Oberhautchen

  2. Beta layer

  3. Meso layer

  4. Alpha layer

Stratum granulosum (+/-)

Stratum spinosum

Stratum germinativum

The fungus infects the skin, presumably from some break in the skin, and infects the deeper layer first. This is observed from the histopathology. It travels along the meso and alpha layer digesting them and prompting hyperkeratosis and dysecdysis. The beta keratin layers apparently take longer to break down and these are only invaded toward the center of the lesion where the fungus has been longest. The outer margins are completely within the alpha layers. This makes some sense. The alpha layers are softer and presumably easier to digest. The problem is that the beta keratin layers remain intact over the advancing wave of fungal hyphae. This prevents topical antifungals from reaching the fungus efficiently. As the disease advances the fungus moves inward into the living layers of the skin and then into the underlying muscle tissue. In some severe cases, I have seen the entire body wall open up to expose the coelomic cavity.

Those with poor immune system function should be careful when dealing with animals suffering from nannizziopsiosis. Though the reports of immunosupressed people infected are few, the potential is present. If you are immunosuppressed from AIDS, steroids for transplants or immune mediated disease, you should consult your MD or Osteopath (DO) before you handle animals infected with this fungus.


karen-24 on December 03, 2015:

Hi there, I am very concerned as my frilled dragon has all the symptoms including the infamous yellow color all around her frills, head and one side of her. I have called my vet and we are booked in to see him tomorrow. Also i am worried about my beardie and myself. Louis has been in close contact with her also sharing food bowls, towels etc. I am very close to her and handle her frequently. Problem is if she has this disease and i have to treat her then i am putting myself at risk as i have stage 5 cancer and i am immune-suppressed due to medication i take. Any sensible advice please?


Ron on July 28, 2015:

No point in fighting this fungus. Once they have it they are on a long road to death. I have lost at least 20 dragons from this fungus. I took in another guys lizards when he couldn't afford it anymore. I have seen it in many different forms, sometimes they get sores, others its dry cracking flaking skin, they loose toes and other parts and it takes a long time. Sad but true if your Beardie has this fungus do it a favor and have it put down. Even with treatment which is very expensive 150 dollars for about a shot glass full, it doesn't go away even after years of use. Ive spent several thousand dollars fighting canv only to have to put them down anyway. I no longer have any with it sadly they are all gone. I have never had it however affect any of my other lizards. I have Ackies, tegu, Quince monitors none of them were infected and are all very healthy. Its just a really messed up thing to have to deal with so sad.

Gatiep on December 20, 2014:

Hi, is there a way I can send you an email, I am having trouble with a couple of things, and wiki is of no help?

Scroll to Continue

Sue Ciampa on November 05, 2012:

I would like to tell you that my bearded dragon is currently fighting YF. We had the expensive tests done, and she has a confirmed case. She is currently taking Voriconizole. Intraconizole did not help. We were using one of the "all natural" products before I had the test done on her. It kept it at bay for a while then she just started busting out with new lesions quite rapidly. My dragon started to display symptoms about 3 months after she contracted mites where she was boarded and we were fighting pneumonia as a result. Can mites transmit YF or could she have been born with it (vet suggested this might be the case). I have kept a photo log of my dragon since this has all started. It is on Photobucket and my username is Suebcee.

vetherppath (author) on August 16, 2012:

Been away on other business for a while, so I have been unable to answer anything, sorry.

Here is a run down on most of the questions.

The fungus is everywhere! Yeah, sounds like a horror movie, I know. This fungus is a saprophyte and is in the soil. Is it airborne? Well, if you live in the panhandle of Texas, it could be. Dust storms! But it doesn't have to be airborne, it is just everywhere.

Prevention is difficult because it is everywhere. The prevailing opinion, and note this is opinion, among exotics vets is that this infection is contracted due to husbandry issues, notably immune suppression of the animals due to stress. Most lizards are not communal animals (marine iguanas being something of an exception). Being housed with other lizards is stressful. They fight and that causes stress. Temperature and other conditions of housing can cause stress. Small cages can cause stress. Stress results in cortisol release from the adrenal glands and suppresses the immune system. Cold suppresses the immune system due to cortisol and the fact that the immune system of ectotherms will shut down below a certain temperature (species has a lot to do with minimum tolerable temperature).

Prevention, at present, seems to be best accomplished by good husbandry and some degree of cleanliness.

As far as pain, yes, it hurts, but reptiles are stoic. Nerves destroyed at the center of the lesion are not the problem. Nerves at the lesion margins are.

As far as homeopathic remedies, stay away is my best advice. Most do not work and many use herbal products that are toxic in the long haul. Those plants with antifungal properties that are ingested are still no use. There have been trials, but the antifungal compounds do not reach any appreciable concentration in the animal's blood, and so are ineffective. Rubbing garlic or ginger on a wound is not recommended either, as it will only make the wound worse by irritating it.

Critter Girl on February 28, 2012:

How is this contracted? Is it passed thtough parents is they have it? Are the eggs contaminated, many questions. Is it air born, or just contagius&? Thanks

Sheryl lynn on February 21, 2012:

Thank you for your knowledge on the subject!! I've lost 2 beardies now due to what I think is the fungus of which you speak and now my current beardie has the same. The symptom being yellowing of the cloacal opening and spreads forth to the legs and abdominal region. I've never seen any brown or blackening of the margins as you said however the top layers of skin come off easily and deeply after time. Is this infection something that they have from the start? If not how can I prevent this horrible thing from infecting my babies??? Thank you so much for your time. Sheryl

Kathe on October 31, 2011:

Thank you so much for the explanation of reptile skin and how the fungus behaves and the clarification of terminiology. I have been fighting the "yellow fungus" with my UROMASTYX for many years, on and off. It appears, more than once, that my uro aegypticus' have been more resistant to the fungus than my malis, even when housed together for years at a time. Perhaps the Malis are more suceptible to poor animal husbandry and resultant immune system problems? I live in Central Florida which I know adds a humidity problem but my guys get all day sun in a wire cage and get brought in at night.

I would like to know about the possibility, when the top layer of skin is deep yellow and waxy-looking, would it be horribly painful to the animal to pull that layer away for better access to the fungus? I would think that

any active nerves would have already been destroyed by the fungus at that point. I am very leery of giving internal medicines due to there side effects.

Has anyone tried feeding ginger, garlic, or other botanicals with anti-fungal properties?

I welcome any answers or feedback at:

Addison on July 13, 2011:

Hey, I am sooo confused if my beardie has it?? He has one yellow spot very little but it is dark and maybee it is something different? If someone can help that would be GREAT!! Thanks

ReptileRevolution from California on March 02, 2011:

Very detailed beardie article--you definitely know your stuff.

Ms. Mike on December 07, 2010:

Excellent article. Unfortunately, I lost my 18 yr old iguana over the summer to this disease. I now have a 7 yr old ig who is responding well to treatment with Voriconazole, Fortaz and SSD. She has been being treated for about 9 months at this point but I will do whatever it takes to save her.

Rae Rae Rae on November 27, 2009:

Great article. I was looking for something educational about the fungus. Nicely written as well. =)

Related Articles