Heartworm disease is a serious condition caused by parasitic worms called Dirofilaria immitis, which primarily affect dogs but can also infect cats and other animals. These worms are transmitted through the bite of an infected mosquito. Once inside the host, the worms can grow up to a foot long and live in the heart, lungs, and blood vessels, leading to severe health issues. Symptoms of heartworm disease may include coughing, fatigue, weight loss, and difficulty breathing. If left untreated, it can result in heart failure or even death. Regular veterinary check-ups and preventive medications are essential for protecting pets from this disease.