What characterizes the structure of OIE?

The structure of the World Organisation for Animal Health (OIE) is characterized by having a World Assembly of Delegates as its highest authority. This assembly comprises delegates from member countries and plays a crucial role in setting policies, approving budgets, and making decisions regarding animal health and welfare issues on a global scale.

This governing body is instrumental in ensuring that the OIE fulfills its mission to improve animal health worldwide, thereby contributing to global food security and public health. The assembly serves as a democratic forum for member states to voice their concerns and collaborate on international standards for animal health and zoonoses.

The other options do not accurately describe the governance structure of the OIE. While the organization does have regional offices, it operates on a more complex framework that includes the World Assembly as the primary decision-making body. It's not governed solely by a central committee nor is it entirely volunteer-operated; the OIE has appointed leadership and staff that work alongside member states to implement its programs and policies effectively.