Its going back a few years now but at 6months old my Akita went really down hill. She was off her food for a few days although not being sick. It seemed all of a sudden over night she got really ill and her weight just fell off.
We took her along to the vet and he said it looked like parvo to him.
She was put on a drip untill the next day. She picked up and was back to full health in days.
As she'd had her boosters I was shocked at this. We had another dog at the time same age and she was fine.