Yellow Fungus Disease in Lizards   Yellow Fungus Disease in Reptiles   What it is: The disease is caused by a fungus, Nannizziopsis sp. The fungus causes scales to discolor, turning yellow, brown and/or gray. It spreads on the skin and to deeper tissues, eventually killing the reptile. In older references, it is called CANV.   Species affected: This fungus has caused disease in many species of lizards and snakes. Bearded dragons and iguanas are the most commonly affected pet lizards.  How it spreads: The fungus can be spread by humans handling the reptiles, by contaminated habitats including substrate and cage furnishings. It is also spread by direct contact between reptiles.  Factors in getting the disease: Temperatures that are too low, along with insufficient uvB lighting and elevated humidity allow the fungus to grow. Any stressed reptile whose immune system is compromised is at risk. Testing: Several types of testing can determine which fungus is involved. PCR (tests for fungal DNA), cultures, and skin biopsies are done. Treatment: If caught early, individual lizards and snakes can be treated with an oral antifungal medication prescribed by a veterinarian.  Prevention: Disinfect your hands after handling any reptile. Environments must be disinfected frequently using 10% bleach, with a contact time of at least 5 minutes. Optimal temperatures, uvB levels, and appropriate humidity levels must be maintained as appropriate for the species. The arrows point to skin infected with Nannizziopsis sp. in 2 bearded dragons.