Parasitology Research

, Volume 116, Issue 10, pp 2721–2726 | Cite as

Extrusion of Contracaecum osculatum nematode larvae from the liver of cod (Gadus morhua)

  • S. Zuo
  • L. Barlaup
  • A. Mohammadkarami
  • A. Al-Jubury
  • D. Chen
  • P. W. Kania
  • K. Buchmann
Original Paper


Baltic cod livers have during recent years been found increasingly and heavily infected with third-stage larvae of Contracaecum osculatum. The infections are associated with an increasing population of grey seals which are final hosts for the parasite. Heavy worm burdens challenge utilization and safety of the fish liver products, and technological solutions for removal of worms are highly needed. We investigated the attachment of the worm larvae in liver tissue by use of histochemical techniques and found that the cod host encapsulates the worm larvae in layers of host cells (macrophages, fibroblasts) supported by enclosures of collagen and calcium. A series of incubation techniques, applying compounds targeting molecules in the capsule, were then tested for their effect to induce worm escape/release reactions. Full digestion solutions comprising pepsin, NaCl, HCl and water induced a fast escape of more than 60% of the worm larvae within 20 min and gave full release within 65 min but the liver tissue became highly dispersed. HCl alone, in concentrations of 48 and 72 mM, triggered a corresponding release of worm larvae with minor effect on liver integrity. A lower HCl concentration of 24 mM resulted in 80% release within 35 min. Water and physiological saline had no effect on worm release, and 1% pepsin in water elicited merely a weak escape reaction. In addition to the direct effect of acid on worm behaviour it is hypothesised that the acid effect on calcium carbonate in the encapsulation, with subsequent release of reaction products, may contribute to activation of C. osculatum larvae and induce escape reactions. Short-term pretreatment of infected cod liver and possibly other infected fish products, using low acid concentrations is suggested as part of a technological solution for worm clearance as low acid concentrations had limited macroscopic effect on liver integrity within 35 min.


Cod Nematode Liver Worm clearance 



The present study was supported by the European Union’s Horizon 2020 research and innovation programme through the grant agreement No. 634429 (Parafishcontrol).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • S. Zuo
    • 1
  • L. Barlaup
    • 1
  • A. Mohammadkarami
    • 1
  • A. Al-Jubury
    • 1
  • D. Chen
    • 1
  • P. W. Kania
    • 1
  • K. Buchmann
    • 1
  1. 1.Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical SciencesUniversity of CopenhagenFrederiksberg CDenmark

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