The practice of optometry by any unregistered or unlicensed optometrist is declared to be a menace and a nuisance and dangerous to the public health and safety; and the board shall promptly abate such practice by filing an action for an injunction in the county in which such practice is conducted. The practice shall be enjoined unless it shall be made to appear that such practitioner is licensed and registered. The board is authorized to file and prosecute such action, and it shall be its duty to do so.