Foul smelly diarrhea in dogs is usually due to viral infection especially canine parvovirus. Parvo is a viral infection in dogs especially in puppies which is caused by a virus called parvovirus. This virus attacks lymphatic system and digestive system of affected dogs. This virus is contagious and can cause diarrhea with blood or without blood, dehydration and vomiting. Parvovirus is transmitted in healthy dogs through feces of infected dogs and contaminated objects. Treatment is done to control Symptoms only.