Jauniaux, T.(1), Boseret, G.(1), Haelters, J.(2), Tavernier, J. (3), Van Gompel, J. (4) and Coignoul, F. (1)
(1) Department of Pathology, Veterinary College, University of Liege, Sart Tilman B43, 4000 Liege, Belgium (2) Management Unit of the North Sea Mathematical Models, Royal Belgian Institute of Natural Sciences, 3e and 23e Linieregimeentsplein, 8400 Oostende, Belgium (3) Royal Belgian Institute of Natural Sciences, Rue
Vautier 29, 1000 Brussels, Belgium (4) Koninginlaan, 40, 8370 Blankenberge, and National Sea Life Centre Blankenberge, Belgium Introduction
Since 1990, the multidisciplinary research network MARIN (Marine Animals Research & Intervention Network) deals with the scientific research of marine mammals stranded along the Belgian and northern France coasts or bycaught. Causes of death are investigated and toxicological analyses performed on collected samples. MARIN also assists in marine mammal rescues and transportation of live stranded animals to rehabilitation centers.
Material and methods
A total of 34 harbour seals (Phoca vitulina) were necropsied and sampled for histology, bacteriology, parasitology, immunohistochemistry, virus isolation and reverse transcriptase-polymerase chain reaction (RT-PCR) 2,4.
Bacteriology
Bacteremia/Septicemia was diagnosed in 5 cases (Escherichia coli –n=3-,
Aeromonas hydrophila –n=1- and haemolytic Streptococcus sp. –n=1-. Morbillivirus detection
In addition of seven seals infected with a morbillivirus during the 1998 summer 4, one other case was positive using two diagnostic techniques 2.
Causes of death
The major non-human associated causes of death were septicemia and bronchopneumonia. In addition, many seals showed evidence of capture in fishing nets and various traumas (gastric perforation and extensive hemothorax).
Acknowledgements
The authors thank A. Lastavel for collecting and providing animals
We also acknowledge M. Domingo for providing tissues of morbillivirus-infected dolphin, A. Trudgett for the monoclonal antibody to the phocine distemper virus, and A. Villers, M. Sarlet, M.P. Desmecht, and F. Verdebout for technical assistance. This work was funded by the Belgian State - Prime Minister's Service, Office for Scientific, Technical and Cultural Affairs (MN/DD/51).
References
1. Bergman, A., B. Jarplid, and B. M. Svensson. 1990. Pathological findings indicative of distemper in European seals. Vet Microbiol 23:331-341.
2. Boseret, G., T. Jauniaux, and F. Coignoul. 2001. Evidence of distemper in harbor seals (Phoca vitulina) stranded from 1990 to 2000 along the coastlines of Belgium and Northern France. European Cetacean Society Annual meeting Roma
3. Harder, T. C., M. Stede, T. Willhaus, J. Schwarz, G. Heidemann, and B. Liess. 1993. Morbillivirus antibodies of maternal origin in harbour seal pups (Phoca vitulina). Vet Rec 132:25:632-633.
4. Jauniaux T., Boseret G., Desmecht M., Haelters J., Manteca C., Tavernier J., Van Gompel J. and Coignoul F. 2001. Morbillivirus in common seals stranded on the coasts of Belgium and northern France during summer 1998, Vet Rec, accepted.
5. Kennedy, S., J. A. Smyth, P. F. Cush, P. J. Duignan, M. Platten, S. J. McCullough, and G. M. Allan. 1989. Histopathologic and immunocytochemical studies of distemper in seals. Vet Pathol 26:97-103. 6. Visser, I. K. G., E. J. Vedder, H. W. Vos, M. W. G. van de Bildt, and A. D. M. E. Osterhaus. 1993. Continued presence of phocine distemper virus in the Dutch Wadden Sea seal population. Vet Rec 133:320-322.
Postmortem findings and causes of death of harbor seals stranded
from 1990 to 2000 along the coastlines of Belgium and Northern
France
Discussion
Animal collection
A surprising finding was the stranding rise starting in 1998. From 1990 to 1997, only 6 seals were available for necropsy while from 1998 to 2000, 28 seals were necropsied. The reasons of such a variation could be manifold, particularly infectious diseases, food shortage and bycatch. For the first period, all were adults, in good nutritional status, with evidence of net entrapment while for the second period, they were mainly pups, in poor nutritional status, with evidence of morbillivirus infection.
Morbillivirus infection
Since 1998, 8 seals stranded on the Belgian and French coastlines were infected by the morbillivirus 2,4. Gross pathological, histological and immunohistological
findings were similar to those reported in seals with distemper 1,5. Septicaemia, bronchopneumonia and encephalitis could result from lymphoid depletion.
All morbillivirus infected seals were weaning pups at the weaning period, at a time where the loss of passive acquired maternal immunity, is known to lead to high susceptibility to PDV 3. It was suspected that PDV infections would continue to occur in some Norh Sea areas 6.
Traumatic lesions
Traumas related to human activities were responsible for the death of 7 seals: 4 net entrapments, 2 gastric perforations with foreign-bodies and 1 seal crushed by a motorbike on a beach.
Gross pathology
The most frequent findings were emaciation (fig.1), acute pneumonia and enteritis (Table 1). Two seals had a severe acute peritonitis associated with gastric perforation due to a foreign body (fig. 2). In 3 seals, numerous hematomas were present in the muscles of the head and thorax associated in 2 cases with multiple rib fractures and hemothorax.
Histopathology
The most frequent lesions diagnosed were acute broncho-pneumonia, subacute interstitial pneumonia, subacute gastritis, and chronic adenitis with Splendore-Hoeppli reaction associated with nematodes larval (fig. 3). Lymphoid depletion and acute to subacute meningo-encephalitis (fig. 4) were also diagnosed.
Mild subacute broncho-interstitial, acute meningoencephalitis and lymphoid depletion cases were frequently associated with morbillivirus infection.
Results.
Fig. 2 : Traumatic gastric perforation Fig. 3 : Granulomatous adenitis with eosinophils infiltration Fig. 4 : Acute to subacute encephalitis -insert: details-Gastric cavity
Duodenum
Foreign body
Gastric perforation
Splendore-Hoeppli reaction Neutrophils, lymphocytes and macrophages infiltration
Table 1: Most frequent findings and causes of death Figure 1 : Severe emaciation
Emaciation 14/28
Bronchopneumonia 8/15
Enteritis 7/15
Bacteremia/Septicemia 6/14 By-catch (confirmed or suspected) 6/19 Trauma (hematoma/gastric perforation) 5/19
