Which of the following combinations describes the clinical signs of heartworm disease?

• A. Vomiting, deep cough, anemia
• B. Irregular heart beat, anemia, exercise intolerance
• C. Deep cough, irregular heart beat, exercise intolerance
• D. Anemia, deep cough, irregular heart beat

Answer: (C)

Heartworm disease in dogs most often affects the lungs and right side of the heart, leading to a characteristic pattern of signs. The deep cough comes from irritation and inflammation of the airways as the worms reside in the pulmonary arteries. As the disease progresses, exercise tolerance declines because the heart and lungs can’t meet the body's needs during activity, causing exercise intolerance. The heart itsel f may develop rhythm disturbances due to right‑sided heart strain and changes in conduction, so an irregular heartbeat can occur. Anemia and vomiting are not typical hallmark signs, though severe cases (like caval syndrome) can present more dramatically. So the combination of a deep cough, irregular heartbeat, and exercise intolerance best captures the common clinical picture.