Feline heartworm is a serious disease caused by the parasite Dirofilaria immitis, which primarily affects cats. The disease is transmitted through the bite of an infected mosquito, and the worms can live in a cat's heart and lungs, leading to severe health issues. Symptoms may include coughing, difficulty breathing, and lethargy, but some cats may show no signs at all. Diagnosis of feline heartworm is challenging, as standard tests for dogs do not work for cats. Treatment options are limited, and prevention is crucial. Pet owners should consult their veterinarians about heartworm prevention medications to protect their cats from this potentially fatal disease.