What are the sign of sickness in a 14 year old Jack Russell terrier?

Signs of sickness in a 14-year-old Jack Russell Terrier may include lethargy, loss of appetite, vomiting, diarrhea, or changes in drinking habits. You might also notice weight loss, difficulty walking or climbing stairs, and changes in behavior, such as increased irritability or hiding. Additionally, symptoms like coughing, difficulty breathing, or excessive thirst could indicate underlying health issues. If you observe any of these signs, it's important to consult a veterinarian for a proper diagnosis and treatment.