Yellow fungus, which is also known as CANV (Chrysosporium anamorph of Nannizziopsis Vriesii) is an infectious fungal infection that affects a wide range of reptiles as well as bearded dragons. There have been some recorded cases of people contracting yellow fungus however the person has had their immune system severely compromised but yellow fungus is not zoonotic meaning that it cannot be contracted from infected reptiles.
Signs and symptoms of yellow fungus can vary by the dragon and are determined by how severe the infection is and how long the dragon has been infected. The earlier signs that will be noticed are lethargy, a decreased appetite, or no appetite at all and weight loss. As it progresses you will notice the more serious symptoms of yellow fungus, patches of yellow, brown and gray scales, crusty dark yellow areas which are stemming from the vent area which resemble shedding but upon the scales coming off reveal open sores that leak pus and possibly blood, open lesions that are slow healing and the slow healing of all the wounds and sores, sunken eyes due to malnutrition and organ failure and eventually necrosis. Yellow fungus is a particularly unpleasant disease because it begins internally and the only way you can know something is wrong is by how the dragon is acting when you notice the later visible symptoms where the scales are damaged the yellow fungus has already been progressing for some time, so it is important that you pursue veterinary treatment as soon as you notice any of the symptoms. This unfortunately makes it very difficult to manage in many instances and it can only be delayed. The veterinarian may choose to treat the dragon with an aggressive course of oral antibiotics/antifungal meds and medicated baths along with topical treatments, these will either slow the progression of the disease or possibly treat it depending on the severity.
Causes of this condition are poor hygiene; it’s very important to practice cleanliness with regards to your dragon’s enclosure, keeping it as clean as possible, and removing old foods and fecal matter as soon as possible to help prevent bacterial and fungal growth. The humidity of the enclosure is also important so it must be measured all the time, humidity that is too high can promote bacterial and fungal growth, the correct humidity you want to achieve is 30% to 40% a little lower can be fine, having low humidity is easier to deal with than having humidity that is too high, one of the ways to bring the humidity down in the tank is to remove the water bowl, you can easily hydrate your dragon by offering them water with a dropper or spray bottle daily. A compromised immune system can also raise the chances of yellow fungus so it’s important to address any medical conditions as soon as possible so that the sickness itself doesn’t lead to further complications such as yellow fungus. The fact that CANV is extremely contagious means that one of the most common causes is simply contracting it from another dragon that already has it. This is why it is important to enact quarantine procedures and strict handwashing between handling your reptiles if you have recently purchased a new dragon, in order to prevent the reptiles you already own from catching anything that the new dragon may have brought into the house, once the new dragon has a clean bill of health you can relax these somewhat but you should always be mindful when handling your reptiles that they can pass things between them.