I invite you to review the signs of parvo and review other pertinent information. This link is to the American Veterinary Medical Association’s website. There is a lot of useful information out there on the prevention and treatment of parvovirus. Unfortunately, there are many myths that circulate as well.
The only thing you can really do to prevent your pet from contracting this serious and potentially fatal disease is to keep vaccines current.
One depressing situation happens over and over again. Pets that are vaccinated with vaccines purchased from pharmacies and local feed stores seem to often contract the disease. Puppies should receive a series of vaccines beginning at 6-9 weeks of age depending on when they are weaned. Vaccines should be properly stored and handled in order to be effective. Vaccines should be boostered at 2-4 week intervals depending on the risk of exposure. All puppies should have at least 2 vaccines after 12 weeks of age. I suspect that the vaccines are improperly stored or administered. Please make sure that your dogs are current on their vaccines.