Causes of dog infection with parvovirus:

1. Usually puppies have very poor adaptability to the environment. Changes in the environment or sudden stimulation can cause them to have a stress response. , making them more susceptible to viruses.

2. If a dog has weak resistance and comes into contact with other dogs carrying the virus, it is likely to be infected.

3. Small dogs that have not been dewormed are easily infected by parasites, causing vomiting and diarrhea, which leads to a decrease in the dog's resistance and is easily infected with parvovirus.

The reasons why dogs are infected with canine distemper:

1. They were infected due to contact with sick dogs and their own insufficient resistance.

2. If the owner touches his dog after coming into contact with the secretions of a sick dog, he may also cause his dog to contract canine distemper.

3. If the virus combines with dust in the air, healthy dogs may be infected after inhaling such dust.