A first increase in mortality was observed in May among these marine mammals. It accelerated in June. More than 70 carcasses were reported, suggesting a mortality rate eight times higher than usual. It raised some questions
according to Jean-François Gosselin, biologist at Fisheries and Oceans Canada.
Stéphane Lair, full professor of veterinary medicine at the University of Montreal, is trying to find answers to several questions.
The harbor seal (above) is much more at risk than other seal species, in which there are no reports of infections.
Photo : Reuters / Mike Blake
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About fifteen harbor seal carcasses were recovered, all in Bas-Saint-Laurent. Their examination revealed that eleven of them had been infected with the H5N1 virus, results that the Canadian Food Inspection Agency should confirm shortly, according to the researcher.
Blame it on the eiders
In all likelihood, it would be these diving ducks which, since they cohabit with harbor seals on the rocks of the St. Lawrence estuary, would have contaminated their mammal neighbors. This neighborhood is particularly strong these days, during the harbor seal whelping season.
The seals will spend more time on the rocks with their calves, but this is also the brood period for common eiders,
raises Mr. Gosselin. It brings the two species together.
If these parental connections are fatal to certain individuals, there is nothing to fear for the species, according to the two researchers.
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The droppings of common eiders could be the source of infection in seals.
Photo : Jessica Latouche
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This kind of epidemic, in wild animals, is something that happens occasionally. It will be associated with a decrease in population, but it is extremely rare for a disease to wipe out a species.
reassures Mr. Lair.
Moreover, there have already been episodes of influenza in seals in Europe and the United States, without necessarily causing mortality, raises Mr. Gosselin. We know this in particular thanks to the antibodies that marine mammals develop when they catch the flu.
The virus transmitted from seal to seal?
It is difficult to know if harbor seals infect each other and if the virus has established itself within this species. MM. Gosselin and Lair have cautious but contradictory intuitions.
According to Fisheries and Oceans Canada biologist Jean-François Gosselin, transmission has not been observed between mammals. Infected seals would therefore be a cul-de-sac for the virus.
Stéphane Lair of the University of Montreal, however, maintains that the number of carcasses is a contrary signal. Given the large number of infected seals, it is believed that yes, there is probably seal-to-seal transmission occurring
he argues.
If the hypotheses of these two scientists differ on this subject, they agree on the fact of telling the population to pay attention to these animals. It is necessary to move away from the carcasses, not to touch them or, if necessary, to use gloves and to disinfect the hands with soap and alcohol, suggests Mr. Gosselin. This is an invitation to caution that Mr. Lair approves. It is a virus that remains potentially pathogenic in humans.
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