Strongyloides stercoralis infection is not endemic in the Republic of Korea (Korea) with a positivity rate of <1% in stool examination. However, there is a risk of hyperinfection in immunosuppressed individuals. It is necessary to determine the seropositivity of S. stercoralis antibodies in Korea. This study investigated the seropositivity of S. stercoralis antibodies in the southeastern area of Korea. From January 2019 to June 2021, serum samples were collected from participants who visited the study center in the southeastern region of Korea for routine health check-ups. We determined serum levels of specific anti-Strongyloides IgG antibodies in 834 samples by enzyme-linked immunosorbent assay. We observed that 92 samples (11.0%) tested showed a positive response. The age of the participants was 51±10.7 years, and 43.4% of them were men. The antibody positivity rate based on the location of the participants’ residence were 12.3% (Gyoungsangnam-do), 10.2% (Busan), and 10.1% (Ulsan), respectively. Total eosinophil count was associated with positive test results (154.8±152.0 per mm³ versus 202.1±178.9 per mm³, P=0.006). Logistic regression analysis revealed that blood eosinophil count, age above 50 years, and residence in Sacheon were factors associated with the positive status of S. stercoralis antibody. Our finding suggests that it is necessary to test for S. stercoralis in actual clinical settings in Korea.

Sparganosis is a parasitic zoonosis caused by plerocercoid larvae of Spirometra species, commonly transmitted through ingestion of infected copepods or raw intermediate hosts. A 51-year-old man presented with a palpable mass in his right thigh. Surgical excision revealed a worm-like structure. Histopathological and serologic findings suggested sparganosis, and PCR amplification of the cox1 gene from paraffin-embedded tissue showed 99% sequence identity with Spirometra erinaceieuropaei (GenBank accession No. KJ599680.1). Praziquantel (75 mg/kg/day for 3 days) was administered, and the patient showed no evidence of recurrence during follow-up. Eosinophilia was not observed; however, positive sparganum antibodies supported the diagnosis. This case demonstrates that molecular identification using mitochondrial genes can be a valuable diagnostic tool, especially when morphological features are limited. Furthermore, it highlights the zoonotic potential of S. erinaceieuropaei and underscores the importance of food safety, hygiene education, and continuous epidemiological surveillance to prevent human sparganosis in endemic regions.