I assume you are talking about a frog, but I have no idea what kind. Some frogs live 20 years or more, others 5-6. I am sorry you lost your pet. Probably most frogs don't require UV light, but some do. You do not say what you are dusting with. Is it just vitamins or are you also using Calcium with D3? I assume you have not introduced any other frogs to the same habitat recently that could have brought some disease (however if you have you might want to consider seeing a vet with your others to be sure they are OK). Since I am new to frogs I probably can not really answer your question but if you posted more detail about history and conditions perhaps someone reading here can. I hear that frogs sometimes just die and that is it! Enjoy them while you have them.