A rare parasitic infection, marked by a persistent bump on an eyelid, has been identified in a California man, representing the first documented case of this specific worm in the United States. The patient, a 74-year-old man, sought medical attention after a bump on his lower left eyelid had persisted for five months.
Initially suspected to be a chalazion, or stye, doctors discovered the anomaly was caused by a nematode, a type of roundworm known as Dirofilaria repens. This parasite is typically found in the skin of dogs and cats and can, in rare instances, infect humans. While this worm has been detected in human infections in Europe and South America, this is the first instance of a person contracting it without leaving the U.S.
The man reported that the bump appeared after an insect bite, accompanied by pain and swelling that later subsided. After surgical removal, microscopic analysis confirmed the presence of the crawling worms within the bump. Doctors noted that the patient had no recent travel history, suggesting the infection was acquired locally in Southern California.
Dirofilaria repens is transmitted to animals through mosquito bites, and humans can become infected similarly. While most human cases are asymptomatic, symptoms can include skin swelling and inflammation.
In the U.S., other species of Dirofilaria, such as Dirofilaria immitis (heartworm in dogs) and Dirofilaria tenuis (found in raccoons), have been recorded in human infections across various states. However, Dirofilaria repens has not been previously detected in U.S. human populations.
Researchers indicated that an increasing mosquito population in California might contribute to a higher risk of such infections. Although the patient experienced no vision loss and recovered fully six months post-surgery, health officials advise vigilance. Dr. Usiwoma Abugo, an ophthalmologist and spokesperson for the American Academy of Ophthalmology, emphasized that while this finding is uncommon, individuals with persistent eyelid bumps should consult an ophthalmologist for evaluation. Prevention primarily involves avoiding mosquito bites and minimizing exposed skin.
