The department of health shall make provision for annual conferences of district health commissioners for the consideration of the cause and prevention of dangerous communicable diseases and other measures to protect and improve the public health. Each board of health or other body or person appointed or acting in place of a board of health shall appoint its health commissioner or health officer a delegate to such conferences. The district board of health shall pay the necessary expenses of such delegate upon presentation of a certificate from the director of health that the delegate attended the sessions of such conferences.