Parvo is a highly contagious disease that is often fatal to puppies. The virus can live in the soil or on other surfaces for a year or more and be able to infect a puppy that comes along and ingests a bit of the dirt or otherwise swallows the parvo virus. Puppies must be vaccinated early to protect them from the disease, but if their mother had immunity the puppies will as well, at least at first.
The first milk that puppies – and other mammals – drink is colostrum. This special milk is rich in antibodies and can be absorbed by very young animals. When puppies are born and nurse from their mothers they get colostrum along with the antibodies for anything she’s immune to, including parvo. As they age their mother’s immunity begins to wear off, leaving the pups vulnerable to disease. A series of puppy shots is essential to replace the mother’s immunity and provide continued protection against parvo and other diseases.