Being overrun, even by a desirable commodity, is an undesirable experience. Even good things can get carried away. Many times, we feel as though our lives our out of control. In dreams, having an infestation of a particular person, object, insect, or animal may be a pictorial representation of feeling overwhelmed.
If the infestation comes from a positive event, it may be a warning from your subconscious that other necessary obligations are being neglected due to your consumption by a singular activity. If the infestation is a categorically negative image, such as rats or mosquitoes, it may be that your life is getting severely undermined. Is the infestation happening in your home, car, or other intimate place?
Are there any others present?