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Postmortem findings and causes of death of harbor
seals stranded from 1990 to 2000 along the
coastlines of Belgium and Northern France
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.
Table 1 Most frequent findings and causes of
death
Figure 1 Severe emaciation
Results.
Bacteriology Bacteremia/Septicemia was diagnosed
in 5 cases (Escherichia coli n3-, Aeromonas
hydrophila n1- and haemolytic Streptococcus sp.
n1-. 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).
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.
Fig. 2 Traumatic gastric perforation
Fig. 3 Granulomatous adenitis with eosinophils
infiltration
Fig. 4 Acute to subacute encephalitis -insert
details-
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.
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). Referen
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