Every person elected or appointed to the office of assessor in an assessor district consisting of unorganized territory, at or before the time of receiving the assessment books, must be bonded for the faithful discharge of the duties of the office, in the state bonding fund or by a corporate surety company authorized to do business in this state, in the penal sum of one thousand dollars. The assessor shall take and subscribe the oath prescribed for civil officers. Failure to be bonded or to take such oath must be deemed a refusal to serve and creates a vacancy in the office.