Dirofilaria immitis, commonly known as heartworm, is a parasitic worm primarily infecting dogs, cats, and other mammals. While it is rare in humans, dirofilariasis can occur if a human is bitten by a mosquito carrying D. immitis larvae. The parasite cannot complete its lifecycle in humans, so it does not develop into an adult heartworm. Instead, the larvae may migrate to the lungs, where they form small nodules that can be mistaken for tumors on imaging studies.
In humans, dirofilariasis is generally asymptomatic or may present with mild symptoms such as cough, chest pain, or, rarely, fever. The lung nodules, also known as “coin lesions,” are often discovered incidentally during imaging for other reasons, as the parasite does not usually cause active disease in humans. Dirofilariasis cases outside the lungs are extremely rare but may occasionally affect other tissues.
Treatment for human dirofilariasis typically involves monitoring, as the nodules often resolve on their own. In some cases, surgical removal may be performed to confirm diagnosis and relieve any symptoms. Preventing dirofilariasis in humans largely involves controlling heartworm in pets, using mosquito repellents, and minimizing exposure to mosquito bites in areas where heartworm is common among animals.
