LAUSR

Human pulmonary dirofilariasis (HPD) is a zoonosis caused by Dirofilaria immitis. Most HPD cases are asymptomatic and are either found on annual health checkups or incidentally identified during investigation of another disease, particularly primary or metastatic pulmonary lung cancer. However, the frequency of Japanese HPD and clinical features remain not well-known. We analyzed data from the Japanese Medical Abstract Society database and identified 69 cases from 1978 to 2022. The incidence of HPD had increased until the 2000s but declined markedly in the 2010s. The incidence was higher in the southwestern and lower in the northeastern region of Japan. Health checkups were the primary diagnostic opportunity. High incidence rates per population were observed in the Chugoku and Shikoku regions. The diagnosis of HPD using a noninvasive procedure is typically difficult due to absence of specific clinical symptoms, and approximately 70% of the cases were detected using video-assisted thoracoscopic surgery. Global warming may increase the incidence of HPD in the northeastern region of Japan, and travel to countries with poor vector control may be a risk factor for HPD transmission. Physicians should consider this parasitic infectious disease when examining patients who present with a solitary nodule in the lungs.