Except as hereinafter provided, the members of such boards of health shall be allowed for the time spent in the performance of their duties, each the sum of $1.50 per day, which together with all bills by them contracted and all sums of money by them expended, shall be audited and paid in the same manner as other county and town expenses. Members of boards of county commissioners elected after July 1, 1965, shall receive no per diem, for serving as a member of a board of health.