There's no specific antidote, but with supportive care from the veterinarian (including rinsing the mouth, anti-vomiting medication, and
possibly subcutaneous fluids), animals do quite well.
In severe cases, usually in young puppies, along with the fever, depression and loss of appetite, there is abdominal pain, vomiting, diarrhea, puffy edema (
subcutaneous fluid swelling) of the head and neck, and
possibly jaundice.