Clinical, pathological, and laboratory diagnoses of diseases of harbour porpoises (Phocoena phocoena), live stranded on the Dutch and adjacent coasts from 2003 to 2016

Cornelis E Van Elk,Peter R W A Van Run,Thijs Kuiken,Marco W G Van De Bildt,Albert D M E Osterhaus,Geoffrey Foster,Jolanda Meerbeek,Paulien Bunskoek

doi:10.1186/s13567-019-0706-3

Abstract

Harbour porpoises (Phocoena phocoena) in the North Sea live in an environment heavily impacted by humans, the consequences of which are a concern for their health. Autopsies carried out on stranded harbour porpoises provide an opportunity to assess health problems in this species. We performed 61 autopsies on live-stranded harbour porpoises, which died following admission to a rehabilitation centre between 2003 and 2016. The animals had stranded on the Dutch (n = 52) and adjacent coasts of Belgium (n = 2) and Germany (n = 7). We assigned probable causes for stranding based on clinical and pathological criteria. Cause of stranding was associated in the majority of cases with pathologies in multiple organs (n = 29) compared to animals with pathologies in a single organ (n = 18). Our results show that the three most probable causes of stranding were pneumonia (n = 35), separation of calves from their mother (n = 10), and aspergillosis (n = 9). Pneumonia as a consequence of pulmonary nematode infection occurred in 19 animals. Pneumonia was significantly associated with infection with Pseudalius inflexus, Halocercus sp., and Torynurus convolutus but not with Stenurus minor infection. Half of the bacterial pneumonias (6/12) could not be associated with nematode infection. Conclusions from this study are that aspergillosis is an important probable cause for stranding, while parasitic infection is not a necessary prerequisite for bacterial pneumonia, and approximately half of the animals (29/61) probably stranded due to multiple causes. An important implication of the observed high prevalence of aspergillosis is that these harbour porpoises suffered from reduced immunocompetence.

Highlights

Biodiversity is in sharp decline due to increasing human pressures on the environment
Harbour porpoises rescued and autopsied The total number of animals admitted for rehabilitation between 2003 and 2016 was 131, of which 61 (47%) were autopsied following death or euthanasia
Animals autopsied originated from the North Sea coasts of Germany (7), Belgium (2) and the Netherlands (52)

Summary

Introduction

Biodiversity is in sharp decline due to increasing human pressures on the environment. There is justifiable concern for the conservation of marine species and ecosystems in areas where humans have a large impact. Anthropogenic activities in the North Sea lead to chemical pollution [2], noise pollution [3], and depleted fish populations [4], which all may affect harbour porpoises. They are vulnerable to chemical pollution because they bioaccumulate and biomagnify lipophilic chemical pollutants [2]. Multiple investigations have found indications for the negative effect of these chemical pollutants on the immune system of harbour porpoises in the North Sea and adjacent waters [5,6,7,8]

Methods

Results

Conclusion