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Diseases of Aquatic Organisms

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DAO 138:97-110 (2020)  -  DOI: https://doi.org/10.3354/dao03440

Pathological findings in North Sea and Baltic grey seal and harbour seal intestines associated with acanthocephalan infections

Jan Lakemeyer1, Kristina Lehnert1, Benno Woelfing1, Iwona Pawliczka2, Martin Silts3, Michael Dähne4, Vivica von Vietinghoff4, Peter Wohlsein5, Ursula Siebert1,*

1Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Foundation, Werftstrasse 6, 25761 Büsum, Germany
2Professor Krzysztof Skóra Hel Marine Station, Department of Oceanography and Geography, University of Gdansk, Morska 2, 84-150 Hel, Poland
3Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu, Estonia
4Stiftung Deutsches Meeresmuseum, Katharinenberg 14-20, 18439 Stralsund, Germany
5Department of Pathology, University of Veterinary Medicine Hannover, Foundation, Bünteweg 17, 30559 Hannover, Germany
*Corresponding author:

ABSTRACT: Grey seals Halichoerus grypus and harbour seals Phoca vitulina are common seal species in the North and Baltic seas and final hosts of Corynosoma acanthocephalans. C. strumosum and C. magdaleni infect the small intestines of both seal species. In contrast to harbour seals, Baltic grey seals in the past have regularly displayed severe C. semerme infections in the caecum and colon, with associated tunica muscularis hypertrophy, inflammation and ulcerations as part of the Baltic seal disease complex (BSDC). Pathogenesis and correlation of acanthocephalan infections with these lesions are still unknown. This study describes the intestinal pathology and parasitic distribution in each seal species. Grey seal (n = 83) and harbour seal (n = 1156) intestines of all age groups and sexes, collected in Poland, Germany and Estonia from 1998 to 2017, were investigated. Most harbour seals came from the North Sea, whereas grey seals were predominantly derived from the Baltic Sea. Both species featured mild to moderate small intestinal infections. Grey seals showed colonic infections not found in harbour seals and featured a chronic erosive to ulcerative, eosinophilic or lympho-plasmacytic colitis with tunica muscularis hypertrophy, indicating still prevailing clinical signs of the BSDC. Harbour seals displayed granulomatous, eosinophilic, lympho-plasmacytic or catarrhal enteritis. The prevalence of acanthocephalan infections in harbour seals increased from 2012 onwards. Furthermore, significant associations between acanthocephalan infection and the presence of intestinal inflammation were found for both seal species. This study suggests that the level of acanthocephalan infection and associated lesions are suitable seal population health indicators, with the colon being a specific target organ for Baltic grey seal health monitoring.


KEY WORDS: Acanthocephala · Corynosoma spp. · Harbour seals · Grey seals · Enteritis · Colitis · Colonic ulcers · North Sea · Baltic Sea


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Cite this article as: Lakemeyer J, Lehnert K, Woelfing B, Pawliczka I and others (2020) Pathological findings in North Sea and Baltic grey seal and harbour seal intestines associated with acanthocephalan infections. Dis Aquat Org 138:97-110. https://doi.org/10.3354/dao03440

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