Why can't photos on my iPhone 4s non camera folders be accessed in Whatsapp?

[iMore Question]

photos in iphone 4s non camera folder could not be accessible in watapp

I recently upgraded to ios8. I transferred some photos to iPhone under my own folder name. I was trying to send few pic via watapp and I found only "camera roll" folder folders is accessible and not my newly created folder. I could not also copy same pics to camera roll.
Any help is appreciated. Thanks