What is a common clinical sign of heartworm disease in dogs?

Coughing or difficulty breathing is a common clinical sign of heartworm disease in dogs. This condition is caused by the presence of adult heartworms in the pulmonary arteries, which can lead to lung damage and increased pressure in the blood vessels around the heart and lungs. As the disease progresses, dogs may exhibit a persistent cough, labored breathing, or exertional dyspnea, particularly after physical activity.

The other options do not typically correlate with heartworm disease. Excessive barking is not a recognized symptom of this condition; while behavioral changes might occur, barking is not specific to heartworms. Fever and vomiting may arise from various other health issues but are not classic signs of heartworm infection. Weight gain is also not associated with heartworm disease; in fact, affected dogs often experience weight loss due to decreased physical activity and other underlying health concerns related to the disease. Therefore, coughing or difficulty breathing is an accurate indicator of heartworm disease in dogs.