An occupational therapist is an individual who meets the requirements under s. 448.05(5m), Wis. Stats., and is licensed by the board to practice occupational therapy. Occupational therapy means the use of purposeful activity with persons who are limited by physical injury or illness, psychosocial dysfunction, developmental or learning disability or the aging process, in order to maximize independent function, prevent further disability and achieve and maintain health and productivity, and encompasses evaluation, treatment and consultation services that are provided to a person or group of persons. No person without a state credential as an occupational therapist may designate himself or herself as an occupational therapist, claim to render occupational therapy services or use the abbreviation O.T. or O.T.R. after the person's name except as provided in s. 448.03(3)(f), Wis. Stats.