Mo. Rev. Stat. § 49.101

In the event of a vacancy in the county offices of county clerk, county auditor, and county assessor, whether such vacancy is by reason of death, resignation, removal, refusal to act, or any other reason, the county commission shall appoint an interim county official to discharge the duties of the office until the governor appoints a successor as provided under state law. At the time of the appointment of a replacement by the governor, the interim appointment shall expire. Such interim appointment by the county commission shall provide the interim county official with all of the protections, bonding requirements, tenants, and other provisions relating to such office.