Abstract

Mass mortalities of harbor seals have occurred in several regions worldwide during the last several decades. Both epidemic infectious diseases and noninfectious causes have been identified as etiology. In fall 2014, an increased mortality of harbor porpoises was observed in Kattegat and along the German North Sea shore.

Pathomorphological investigations were conducted on 21 harbor porpoises (Phoca vitulina) from the North Sea. Immunohistological, electron microscopical, bacteriological, virological and molecular investigations were performed to identify the causative agent.

Purulent to necrotizing inflammation was observed in nasal and tracheal tissue. Necrotizing bronchitis/bronchiolitis as well as adenitis of bronchial glands were found in the lung. Furthermore, purulent and (pyo)granulomatous pneumonia was identified, the latter associated with endoparasites. Immunohistology demonstrated the presence of intralesional nucleoprotein of influenza virus A that was identified as influenza A/H10N7 after virus cultivation and sequencing. Bacteriology isolated primarily streptococci.

Increased mortality in harbor porpoises from the North Sea can be attributed to an influenza A virus infection. Secondary bacterial infections and pulmonary endoparasites most likely contributed to mortality.

* Presenting author