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9 of 10 Great Cormorants Examined in South Korea Carried a Newly Recorded Tapeworm

Great cormorant in flight in Suwon, South Korea
Research · Disease, parasites & microbiology

A tapeworm not previously documented in South Korea has been identified in resident great cormorants (Phalacrocorax carbo sinensis). Nine of ten birds examined carried Paradilepis scolecina, giving a prevalence of 90% in this small sample.

P. scolecina is an intestinal tapeworm of fish-eating birds. Its life cycle is linked to freshwater food webs, with copepods and fish able to act as successive intermediate hosts, so a first national record also raises the question of whether a local transmission cycle is established in Korean freshwater systems.

The cormorants had been lethally controlled by local authorities at Paroho Lake in Yanggu County, Gangwon Province, in April 2024 and donated for scientific examination. Adult tapeworms were recovered from the small intestine. Among the nine infected birds, worm counts ranged from two to 1,250, with a mean intensity of 280.1 per infected host.

Morphology and DNA confirmed the first Korean record

The researchers combined light microscopy, scanning electron microscopy and ribosomal and mitochondrial DNA markers to identify the worms. A diagnostic feature was the hook-bearing rostellum at the front of the tapeworm, which carried 20 hooks arranged in two rows. The morphological and genetic evidence together supported identification as P. scolecina.

Scanning electron microscopy also revealed a previously undescribed surface structure on the cirrus, the male copulatory organ: rose-thorn-shaped spines interspersed with fine filament-like structures. The authors describe this as the first such ultrastructural observation reported in the family Gryporhynchidae.

The Korean life cycle is still unknown

P. scolecina has a complex food-web life cycle. Related evidence indicates that copepods and freshwater fish can serve as successive intermediate hosts, while fish-eating birds such as cormorants carry the adult worms. No intermediate fish host has yet been confirmed for the parasite in South Korea.

The authors suggest that the increasing year-round residency of great cormorants in parts of South Korea could increase opportunities for local transmission by maintaining regular contact with freshwater food webs. They also raise possible implications for wild fish and aquaculture if economically important fish prove to be intermediate or paratenic hosts. These are hypotheses and ecological risks to investigate, not effects demonstrated by this study.

The study did not assess tissue damage or health effects in the examined cormorants. The high parasite burdens therefore show that infection can be intense in some individuals, but do not by themselves establish how strongly the worms affected the birds.

Sources and image credit

  1. Lee, H. W., Lee, H.-E., Lee, C., Opara, E., Oh, H., Bia, M. M., Kim, S., Lee, S., Lee, S.-H., & Choe, S. (2026). First record of Paradilepis scolecina (Rudolphi, 1819) Hsü, 1935 (Cestoda: Gryporhynchidae) in Republic of Korea with notes on ultrastructure and ecological risk in great cormorants, Phalacrocorax carbo sinensis (Staunton, 1796) (Aves: Phalacrocoracidae). International Journal for Parasitology: Parasites and Wildlife, 29, 101211. https://doi.org/10.1016/j.ijppaw.2026.101211Primary peer-reviewed article available online 10 February 2026. Ten resident great cormorants from Yanggu County, South Korea, were examined; nine carried Paradilepis scolecina, the first record of the tapeworm in the country. The article is open access under CC BY-NC-ND 4.0.

Image: Mathew Schwartz / Wikimedia Commons — wild great cormorant (Phalacrocorax carbo sinensis) in flight near a lake in Suwon, South Korea, photographed 21 December 2016. Representative South Korean species photograph, not one of the birds examined in the study. · CC BY 3.0 — https://creativecommons.org/licenses/by/3.0/ · Source

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