Which of the following symptoms can indicate a serious respiratory issue in a cat?

Rapid and shallow breathing in a cat is a significant indicator of a serious respiratory issue. This pattern of breathing can suggest that the animal is not receiving adequate oxygen or is experiencing distress in the respiratory system. It may be a sign of conditions such as pneumonia, pleural effusion, or obstructive airway disease. In a healthy cat, breathing should be regular, and any deviation from this, particularly rapid and shallow breaths, can signify underlying health problems that require immediate veterinary assessment.

Persistent vomiting, sudden lethargy, and excessive grooming can indicate health issues, but these symptoms are not specifically tied to respiratory distress. While lethargy can be a general sign of illness and may correlate with respiratory problems if the cat is fatigued from the effort of breathing, it is not as direct an indicator of respiratory compromise as rapid and shallow breathing is.