How can I remove 1200+ contacts duplicates from my iPhone and iPad?

I have duplicate contacts on my iphone and ipad; but not on Outlook and iCloud. Running windows 7 64bit. I have 2494 contacts in outlook and icloud. There 3753 on my iphone and 3785 on my 1pad. Well over 1200 duplicates on both. Sync address book is NOT checked in itunes. Besides I have not synced my ipad or iphone with itunes in weeks and this has happened recently. How can I remove the duplicates? Why did it happen? How do I prevent it from happening again?