Our Daisy had parvo as a puppy. not as young as your Serenity though. It itook three days but after plasma and blood she came through it. My prayers and thoughts are w/ you . There is alot more they know about parvo in the 14 years since Daisy had it.
Lucky- GSD Rescue 2/16/2002
Thunder : adopted 1/25/2013
Miss Chevy Cruz - 1/25/2013-1/29/15