Heartworm disease is a severe and potentially fatal condition caused by parasitic worms living in the heart and pulmonary arteries of infected animals. Dogs, cats, and ferrets are the most common hosts for these parasites, which are transmitted through the bite of an infected mosquito. Understanding the life cycle of heartworms is crucial for prevention and treatment. Recognizing the signs and symptoms early can save lives, with coughing, lethargy, and weight loss being some of the warning signs in pets.