So, with your remedy which is good on your site with Parvovirus in puppies. You can add some of the following. I will state the reasoning as well for this natural remedy:
1. Hot English Mustard Powder
Reasoning: Parvovirus is an intestinal parasite (Bacteria, viral etc). The bacteria multiply in the intestines similar to that of worms. Administering Hot English Mustard powder eliminates and helps eradicate these parasites inside the intestines and bowel.
Dosage: A tiny little bit - around the size of a small capsule 5mm size.
Administration: This should be administered dry, and directly onto the tongue/toward the back of the throat. Have a syringe ready with some boiled and cooled (sterile) water to wash down the mustard powder. It does burn, but subsides very fast. As soon as the pup/dog has swallowed most of it, slowly syringe it down with some cool (room temperature) water. Any change in temperature may affect the very sensitive intestinal area. You can either use your finger to put it at the back of the tongue (safest), or a spoon (not advised as most pups will bite down on this and damage their teeth).
References: Parvo rescue missionary - rescuing more than 22 out of 24 puppies since 2006.