Did algal toxin and Klebsiella infections cause the unexplained 2007 mass mortality event in Danish and Swedish marine mammals?
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
An unusual mass mortality event (MME) of harbour seals (Phoca vitulina) and harbour porpoises (Phocoena phocoena) occurred in Denmark and Sweden in June 2007. Prior to this incident, the region had experienced two MMEs in harbour seals caused by Phocine Distemper Virus (PDV) in 1988 and 2002. Although epidemiology and symptoms of the 2007 MME resembled PDV, none of the animals examined for PDV tested positive. Thus, it has been speculated that another – yet unknown – pathogen caused the June 2007 MME. To shed new light on the likely cause of death, we combine previously unpublished veterinary examinations of harbour seals with novel analyses of algal toxins and algal monitoring data. All harbour seals subject to pathological examination showed pneumonia, but were negative for PDV, influenza and coronavirus. Histological analyses revealed septicaemia in multiple animals, and six animals tested positive for Klebsiella pneumonia. Furthermore, we detected the algal Dinophysis toxin DTX-1b (1–115 ng g−1) in five seals subject to toxicology, representing the first time DTX-1b has been detected in marine vertebrates. However, no animals tested positive for both Klebsiella and toxins. Thus, while our relatively small sample size prevent firm conclusions on causative agents, we speculate that the unexplained MME may have been caused by a chance incidence of multiple pathogens acting in parallel in June 2007, including Dinophysis toxin and Klebsiella. Our study illustrates the complexity of wildlife MMEs and highlights the need for thorough sampling during and after MMEs, as well as additional research on and monitoring of DTX-1b and other algal toxins in the region.
| Originalsprog | Engelsk |
|---|---|
| Artikelnummer | 169817 |
| Tidsskrift | Science of the Total Environment |
| Vol/bind | 914 |
| Antal sider | 9 |
| ISSN | 0048-9697 |
| DOI | |
| Status | Udgivet - 2024 |
Bibliografisk note
Funding Information:
The authors would like to thank Thomas Max for great instructions and help in the laboratory at The Alfred Wegener Institute, and Esben Nielsen and Gosha Sylvester for helping with the freeze-drying process. We further acknowledge Mette Sif Hansen, Morten Abildstrøm and Niels Worm for sample collection, Anna Olesen and Helene Munk Sørensen for providing us with algal monitoring data, and Malthe Aslak Nebel Sohn for help with graphics. Thanks also to Philipp Hess for providing us with very helpful articles and knowledge especially regarding DTX-1/1b, and to Iben Stokholm for discussions about possible viral infections. Finally, we would like to thank Bodil Kruse for assistance with morbillivirus and coronavirus screenings, Kurt Handberg Jensen, Poul H. Jørgensen, Ahlman Nielsen and Susanne Jespersen for assistance with the influenza screenings, and Anne Marie Lassen Nielsen and Thijs Kuiken for their help with virus and bacteriology screenings. The study was funded by the Danish Nature Agency, the Velux Foundations (grant 123012) to MTO, and the Independent Research Fund Denmark (grant 9040-00248B) to NL.
Funding Information:
The authors would like to thank Thomas Max for great instructions and help in the laboratory at The Alfred Wegener Institute, and Esben Nielsen and Gosha Sylvester for helping with the freeze-drying process. We further acknowledge Mette Sif Hansen, Morten Abildstrøm and Niels Worm for sample collection, Anna Olesen and Helene Munk Sørensen for providing us with algal monitoring data, and Malthe Aslak Nebel Sohn for help with graphics. Thanks also to Philipp Hess for providing us with very helpful articles and knowledge especially regarding DTX-1/1b, and to Iben Stokholm for discussions about possible viral infections. Finally, we would like to thank Bodil Kruse for assistance with morbillivirus and coronavirus screenings, Kurt Handberg Jensen, Poul H. Jørgensen, Ahlman Nielsen and Susanne Jespersen for assistance with the influenza screenings, and Anne Marie Lassen Nielsen and Thijs Kuiken for their help with virus and bacteriology screenings. The study was funded by the Danish Nature Agency , the Velux Foundations (grant 123012 ) to MTO, and the Independent Research Fund Denmark (grant 9040-00248B ) to NL.
Publisher Copyright:
© 2024 Elsevier B.V.
ID: 383704512