sql server replication: In DTS whenever the data was imported to tables in replication, the merge
tracking triggers were not getting fired.

There was an option FAST LOAD / BULK load (not sure) which was required to
be deselected.

I am using SSIS and find that the triggers are not fired even here. Does
anyone know which option in SSIS need to be deselected to fire the
replication triggers?

Please take a look here:
http://msdn2.microsoft.com/en-us/library/ms141237.aspx
There is an option to type FIRE_TRIGGERS in the Advanced Editor...
HTH,
Paul Ibison