Should your rug have either of these problems, place it in direct sunlight outdoors. Several exposures to sunlight (8+/- hours total) the mildew or mold should be obliterated. Another alternative should the problem persist would be to clean the rug yourself - Try our Stain Removal Guide for assistance.
If the problem persists, send the rug out to a reputable oriental rug cleaning plant. They can wash the rug with particular additive shampoos to treat and control mildew and mold.