Friday, January 28, 2011

Oh, Canada! PDV erupts?

ProMED Mail 22 January 2011, a report from my homeland...

Premature deaths of harp seal adults and pups have risen in recent weeks, with storm surges in the Atlantic bringing corpses ashore in January 2011, mainly along the coast of Newfoundland and Labrador, but also in the St. Lawrence region. Confirmed deaths are currently in the low hundreds so far, but there are also reports of premature births, or “early pupping”. Harp seals (Phoca groenlandica) migrate south on the east coast of Canada in late fall/early winter to breed, with regular parturition occurring at the end of February and early March. On average, about a quarter of pups in their first year suffer premature death—this does not account for the washed up seals, as this mortality soon declines with age, leveling off to approximately four percent.

A possible cause of the mortalities is porcine distemper virus (PDV), which is enzootic in the population. PDV is a morbillivirus (genus shared by viruses causing human disease, including measles), part of the paramyxoviridae family. Though epizootics have slain thousands of seals across the Atlantic, major viral epizootics have not been previously observed in Canada, possibly due to herd immunity, with 83% of seals in a Canadian sample seropositive for PDV. Poor ice conditions and herd size may contribute to the susceptibility of the population to epizootic.


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