Yellow Fungus, which is more scientifically referred to as Chrysosporium Anamorph of Nanniziopsis vriesii (CANV), is an aggressive fungus infection. Because of it's aggressiveness, if you suspect yellow fungus in your beardie it is HIGHLY recommended to seek the advice of a veterinarian. In many cases yellow fungus can be fatal but early detection can greatly increase your odds.
In the early stages of infection expect to see dry and crusty looking lesions on scales along with discoloration. In addition to this, these trouble spots may be retained when your beardie sheds which may also become more frequent at this stage of the disease. As the disease worsens, you will likely see some of the first affected areas turning black and beginning to essentially rot away. If the fungus starts on limbs or the tail, it is possible for these to even fall off. At this point, wounds may begin leaking a pusslike substance as well. Lastly, it is likely that your dragon at this point is lethargic, not eating (or eating very little) and possibly grumpy/aggressive.
So where does yellow fungus come from? Essentially your dragon will only come in contact with the pathogen IF they are touched or touch something/someone that also touched the infected dragon. So once again the topic of husbandry arises. Keeping you Beardie clean with a weekly bath, housing your beardie in an appropriate size enclosure, keeping your beardie's enclosure clean, keeping only ONE bearded dragon per habitat, etc. Remember YF is a pathogen that's highly communicable between beardies so keeping multiple bearded dragons together can help spread the fungus quickly.
If you suspect that your beardie may have yellow fungus, contact an exotics veterinarian immediately. Because it is so aggressive, it can affect internal organs as well. A veterinarian can help determine the severity of the disease and will most likely prescribe an antibiotic or antifungal. Some herpetologists will suggest a 5-10 minute betatine or chlorhexidine bath for preventative treatments.
