The board of county commissioners of each county shall appoint a licensed professional engineer, whose official title shall be county engineer. Such appointment may be terminated without cause on June 1 of any year by a majority vote of the board of county commissioners or may be terminated for cause at any time by the board of county commissioners or by order of the secretary of transportation for incompetency or by dissolution of a county engineer district: Provided, That all appointments of county engineers shall be approved by the secretary of transportation. The provisions of this section shall not disqualify any county engineer who is not a licensed professional engineer and who was holding office as county engineer on June 30, 1961, and any such person shall be eligible for appointment as a county engineer.