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Diseases of Aquatic Organisms

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DAO 127:57-63 (2017)  -  DOI:

Parasites in the inner ear of harbour porpoise: cases from the North and Baltic Seas

Maria Morell1,*, Kristina Lehnert2, Lonneke L. IJsseldijk3, Stephen A. Raverty1,4, Peter Wohlsein5, Andrea Gröne3, Michel André6, Ursula Siebert2, Robert E. Shadwick

1Zoology Department, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
2Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, 25761 Büsum, Germany
3Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands
4Animal Health Center, Ministry of Agriculture, Abbotsford, British Columbia V3G2M3, Canada
5Department of Pathology, University of Veterinary Medicine Hannover, 30559 Hannover, Germany
6Laboratori d’Aplicacions Bioacústiques, Universitat Politècnica de Catalunya, BarcelonaTech (UPC), 08800 Vilanova i la Geltrú, Spain
*Corresponding author:

ABSTRACT: Peribullar sinuses of harbour porpoises Phocoena phocoena are parasitized with high prevalence by the nematode Stenurus minor. The effect of S. minor on the hearing ability of this species is still undetermined. Here, we review the occurrence of S. minor in the inner ear of harbour porpoises recovered from strandings in the North and Baltic Seas. In particular, we present the results from ears collected in German and Danish waters from 2002 to 2016 and from Dutch waters from 2010 to 2016. While the prevalence of S. minor in pterygoid and peribullar sinuses and tympanic cavity was high in harbour porpoises (66.67% in our cases), its prevalence in the cochlea was rare. Only 1 case out of 129 analysed by either histology, electron microscopy or immunofluorescence showed the presence of a nematode parasite morphologically consistent with S. minor at the most basal portion of the right cochlea. This individual also had severe haemorrhage along the right cochlear spiral, which was likely caused by ectopic S. minor migration. Although this animal might have had impaired hearing in the right ear, it was otherwise in good body condition with evidence of recent feeding. These findings highlight the need to study the effect of parasites on hearing, and other pathological changes that might impair appropriate processing of acoustic information.

KEY WORDS: Harbour porpoise · Phocoena phocoena · Nematode · Stenurus minor · Inner ear · Parasites · Cochlea · Haemorrhage

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Cite this article as: Morell M, Lehnert K, IJsseldijk LL, Raverty SA and others (2017) Parasites in the inner ear of harbour porpoise: cases from the North and Baltic Seas. Dis Aquat Org 127:57-63.

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