Question: my dog is vomiting has diarrhea and is lethargic?
Answer: Any kind of infection -- including serious ones such as parvovirus, distemper, kennel cough, leptospirosis, and heartworm disease -- can make your dog lethargic. Parvovirus is spread through feces. Symptoms of parvo can include lethargy, vomiting, diarrhea, and abdominal pain.