Can editors review a manuscript and make a decision if they cannot find any reviewers? I had submitted a manuscript to an International Journal few months before. It is already 5 months. But the status is still showing "under review". Since it is getting late, so I contacted to the Journal stating the current status. I got a reply that they have contacted a number of reviewers, but no one shows interest to review it. At present they have sent the manuscript to the editor. 

So whether an Editor can reject it most probably? or can review my manuscript to make a proper decision?
The editor certainly has the power to reject an article without having it reviewed.  If they can't find a suitable reviewer, this is probably what would happen, unfortunately for you.

In some cases the editor might have the authority to accept it without an outside review, but this would depend on the policies of the specific journal.  Anyway, if they were planning to do this, they probably would have already done it.