It may be caused by internal inflammation of the dog, infection with parvovirus, canine distemper and other diseases. In this case, after handling the dog's body, the breeder should carefully clean and disinfect the items, corners and items used by the dog in the home. Avoid virus residues. Spring and autumn are the peak seasons for dog-infected diseases. It is recommended that breeders vaccinate dogs every day to prevent virus infection and reduce dog mortality.