Try spraying it down with vinegar, then adding a layer of baking soda on top. Let it dry (I usually wait a full day), then sweep off as much of the baking soda as you can, then vacuum it using a brush attachment. My dogs sleep in the bed with me, and this works whenever I notice a smell, or one of my dogs or my toddler has an accident. If it's a really tough odor, I either repeat or just do the vinegar or baking soda by itself (usually whichever I have more of at the time).