Question: What causes thrush?
Answer: It’s not known whether thrush is caused by a bacteria or a fungus but most agree that it persists in the soil. There is also speculation that the organism responsible exists in the horse itself. It thrives in damp anaerobic conditions—areas that don’t get oxygen, like the clefts of your horses’ hooves. A hoof filled with moist dirt and manure is susceptible to thrush. You may not notice thrush during very dry weather, but when wetter weather persists, the infection may increase.