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Kidney Worms Were Found in 38% of Wild Boar Examined in Southwestern South Korea

Two young wild boar standing side by side
Research · Disease, parasites & microbiology

A survey of wild boar (Sus scrofa coreanus) in southwestern South Korea found the kidney worm Stephanurus dentatus in 64 of 167 examined animals, an overall prevalence of 38.3%. Infected animals carried an average of 6.8 adult worms.

S. dentatus is a parasitic nematode whose larvae migrate through tissues before the adults settle around the urinary system. In domestic pigs, migrating larvae and heavy infections can damage the liver and other tissues, although this study did not determine how much disease the parasite caused in the sampled wild boar.

The animals were examined between 2009 and 2019. Researchers dissected the kidneys, ureters and surrounding fat and recovered 438 adult worms.

Males and females had similar infection levels

Infection was detected in 40.7% of males and 35.5% of females, with no clear difference between the sexes. The mean worm burden was likewise similar: infected males carried 7.0 worms on average and infected females 6.6.

Stereomicroscopic images of Stephanurus dentatus collected from wild boar kidneys and surrounding fat
Stephanurus dentatus recovered from wild boar kidneys and perirenal fat. A–B: encysted worms in the renal pelvis; C: worms in cysts in perirenal fat; D: an isolated adult female. Ahn et al. (2026), Parasites & Vectors, CC BY 4.0.

Kidney worms occupied several urinary tissues

The parasites occurred in the renal pelvis, around the kidneys and in the ureteral wall. S. dentatus eggs are shed mainly in urine, and infective third-stage larvae can enter a new host through the skin, contaminated food or water, or after being ingested in earthworms that act as transport hosts. The larvae then migrate through tissues before adults settle around the urinary system. This life cycle helps explain why examining only the kidney lumen can miss infections in surrounding fat and ureters.

Microscopy confirmed characteristic anatomical features of the species. Sequencing of the 18S rRNA gene — a slowly changing genetic marker often used to compare evolutionary relationships — showed 99.7–99.9% identity with reference sequences. The resulting genetic family-tree analysis supported placement of S. dentatus within Chabertiidae rather than its traditional placement in Syngamidae, and the authors argue that the subfamily Stephanurinae should be reclassified accordingly.

Prevalence did not show disease severity

The study did not collect information on the overall health of the sampled wild boar, so the 38.3% prevalence shows how common infection was but not how much disease it caused in these animals. In domestic pigs, migrating larvae and heavy infections are known to damage the liver and other tissues, but such pathological effects were not evaluated in this wild-boar dataset.

Local prevalence ranged widely, but sample sizes were uneven

Prevalence was 17.9% in Suncheon and 42.1% in Gwangyang. It reached 75.0% in Boseong, while neither of the two animals from Haman was infected. The latter two estimates are especially uncertain because only four animals were sampled in Boseong and two in Haman. The authors therefore describe the geographic pattern as spatially heterogeneous and potentially focal rather than as a precise ranking of regional infection levels.

This is the first epidemiological assessment of S. dentatus in wild boar in South Korea.

Sources and image credit

  1. Ahn, K.-S., Ahn, A.-J., Lee, S.-H., Kwak, D., Lee, J., & Shin, S. S. (2026). Epidemiology, morphology, and molecular characterization of Stephanurus dentatus (Nematoda: Syngamidae) in wild boars from southwestern South Korea. Parasites & Vectors, 19, 218. https://doi.org/10.1186/s13071-026-07303-6Primary open-access research article published 10 April 2026 under CC BY 4.0. Of 167 wild boar examined from 2009–2019, 64 (38.3%) were infected with Stephanurus dentatus, with a mean intensity of 6.8 worms per infected animal. A total of 438 adult worms were recovered. Infection prevalence and worm burden did not differ significantly by host sex. Four 18S rRNA sequences showed 99.7–99.9% identity with reference sequences and supported placement in Chabertiidae. Local sample sizes were strongly unbalanced.

Image: Evelyn Simak / Geograph — two young wild boar at Bridge Farm, England, 29 November 2008; representative image, not animals from the South Korean study. Source: Wikimedia Commons. · CC BY-SA 2.0 · Source

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