It is quite a challenge to differentiate between signs of illness and fatigue in dogs due to similar symptoms like loss of appetite and lethargy. Signs of illness to look out for after you find a puppy in Venice include sneezing, coughing, vomiting, or diarrhea. In contrast, signs of fatigue may include a fall in activity level or a lack of interest in walks or play. However, if you are unsure whether your dog is ill or merely exhausted, it is vital to consult your veterinarian.