Host Lines:

[Time of last update] HOST;
Host Name (string);
Status (OK/DOWN/UNREACHABLE);
Last Check Time (long time);
Last State Change (long time);
Acknowledged (0/1);
Time Up (long time);
Time Down (long time);
Time Unreachable (long time);
Last Notification Time (long time);
Current Notification Number (#);
Notifications Enabled (0/1);
Event Handlers Enabled (0/1);
Checks Enabled (0/1);
Flap Detection Enabled (0/1);
Host is Flapping (0/1);
Percent State Change (###.##);
Scheduled downtime depth (# - 0/1 ???);
Failure Prediction Enabled (0/1);
Process Performance Data(0/1);
Plugin Output (string) 

Service Lines:

[Time of last update] SERVICE;
Host Name (string);
Service Description (string);
Status (OK/WARNING/CRITICAL/UNKNOWN);
Retry number (#/#);
State Type (SOFT/HARD);
Last check time (long time);
Next check time (long time);
Check type (ACTIVE/PASSIVE);
Checks enabled (0/1);
Accept Passive Checks (0/1);
Event Handlers Enabled (0/1);
Last state change (long time);
Problem acknowledged (0/1);
Last Hard State (OK/WARNING/CRITICAL/UNKNOWN);
Time OK (long time);
Time Unknown (long time);
Time Warning (long time);
Time Critical (long time);
Last Notification Time (long time);
Current Notification Number (#);
Notifications Enabled (0/1);
Latency (#);
Execution Time (#);
Flap Detection Enabled (0/1);
Service is Flapping (0/1);
Percent State Change (###.##);
Scheduled Downtime Depth (# - 0/1 ???);
Failure Prediction Enabled (0/1 ???);
Process Performance Date (0/1);
Obsess Over Service (0/1);
Plugin Output (string)

Program Line (2nd Line of log):

[Current Time] PROGRAM;
Program Start Time (long time);
Nagios PID (#);
Daemon Mode (0/1);
Last Command Check (long time);
Last Log Rotation (long time);
Notifications Enabled (0/1);
Execute Service Checks (0/1);
Accept Passive Service Checks (0/1);
Enable Event Handlers (0/1);
Obsess Over Services (0/1);
Enable Flap Detection (0/1);
Enable Failure Prediction (0/1 ???);
Process Performance Data (0/1)