The reason why parvovirus causes diarrhea is due to the virus's ability to infect and damage the cells lining the small intestine. The damaged intestinal cells are unable to absorb nutrients and water properly, resulting in the passage of loose, watery stools. Additionally, the infection leads to an increased secretion of fluids into the intestines, contributing to the diarrhea.
Parvovirus is a highly contagious disease and can be life-threatening, especially in young puppies. If your puppy is experiencing symptoms of parvo, it is important to seek immediate veterinary attention for proper diagnosis and treatment.