For the best outcome for parovirus, they should be hospitalized getting IV fluids, medicatons for nausea, blood sugar support and antibiotics - intravenously.
The shaking an illness you report is not normal and can indicate electrolyte or blood sugar (low) problems.
Until you can see your vet, what can we try at home and is over the counter to help?- You can try to offer small amounts of pedialyte for hydration and electrolytes. You can even purchase a dropper from your local pharmacy to offer the water/pedialyte mixture by mouth.- A calorie dense nutritional supplement such as nutrical (LINK HERE)- Another option would be baby food. If you are going to try this, please purchase baby food that does not have any ingredients such as garlic or onion.Many baby foods now will only have the ingredients of the item and water...for example chicken and water. But they will not have any other salts or seasonings. This is what you need. Just chicken and water or beef and water for example.