Abstract
Toxocariasis is a zoonotic helminth infection caused by Toxocara canis or Toxocara cati. While it has traditionally been regarded as a pediatric soil-transmitted disease, recent reports from Japan suggest that an increasing number of adult-onset cases are potentially associated with foodborne transmission. Ocular involvement in adults can also result in severe visual impairment. However, nationwide data describing the epidemiological and clinical characteristics of hospitalized patients in Japan are limited. We conducted a nationwide retrospective study using the Japanese Diagnosis Procedure Combination database from the fiscal years 2014 through 2020. Hospitalized patients with toxocariasis were identified using ICD-10 code B83.0. Demographic characteristics, organ involvement, geographic distribution, and treatment patterns were descriptively analyzed. Forty-one patients with toxocariasis were identified. The median age was 53 years (range, 10-89 years), and 63% of the patients were male. None of the patients were younger than 10 years. Ocular involvement was the most frequent presentation (41%), and ophthalmologic surgery, including pars plana vitrectomy, was performed in 24% of the cases. Patients who were hospitalized were predominantly from the Kinki (32%) and Kyushu-Okinawa (29%) regions. Albendazole was administered to 54% of the patients, with a median inpatient treatment duration of 3 days (inpatient administration only). In Japan, toxocariasis requiring hospitalization predominantly affects middle-aged and older adults and is frequently associated with ocular involvement requiring surgical intervention. The adult-dominant patterns and geographic clustering in Western Japan may reflect region-specific exposure characteristics. Although limited to hospitalized patients and administrative data without diagnostic validation, these findings provide the first nationwide overview of severe toxocariasis requiring hospitalization in Japan and contribute to understanding its clinical and epidemiological profile.