https://beardeddragongeek.com/yellow-fungus-in-bearded-dragons-causes-diagnosis-treatment-and-prevention/

Yellow fungus disease, scientifically known as Chrysosporium anamorph of Nannizziopsis vriesii (CANV), is a severe fungal infection affecting bearded dragons (Pogona species). It manifests as yellow to brown crusty patches on the skin, often leading to lesions and sores as the infection progresses. This condition is highly contagious and can spread quickly among reptiles in close proximity.

Causes: The disease is primarily caused by the fungus CANV, which thrives in humid, unclean environments. Poor husbandry practices, such as inadequate cleaning of the habitat and improper humidity levels, can contribute to the spread of the fungus.

Diagnosis: Diagnosis typically involves a combination of clinical examination and laboratory tests. Veterinarians may take skin biopsies or swabs for fungal culture and microscopic examination to confirm the presence of the fungus.

Treatment: Treatment is challenging and often requires a combination of antifungal medications, both topical and systemic. Supportive care, including maintaining optimal husbandry conditions, is crucial. In severe cases, surgical debridement of infected tissue may be necessary.

Prevention: Preventing yellow fungus disease involves maintaining a clean and well-regulated environment. Regularly disinfecting the habitat, ensuring proper humidity and temperature levels, and providing a balanced diet to boost the immune system can help reduce the risk of infection. Quarantining new or sick reptiles is also essential to prevent the spread of the fungus to healthy individuals.