Photo credit: Atlantic white-sided dolphins by batwrangler via Flicker
Here we report a case of fatal infection with the highly pathogenic H5N1 avian influenza virus (AIV H5N1) in a white-sided dolphin (Lagenorhynchus acute). This juvenile male dolphin was found dead on a beach near Rimouski, Quebec on September 5. The carcass was presented by the Quebec Marine Mammal Emergency Response Network (RQUMM) to the CWHC – Quebec regional center for analysis.
The animal was in good physical condition, suggesting death from an acute event. Apart from the presence of low intensity parasitic infections, no gross lesions were observed in the animal. Histopathological examination of the tissues revealed the presence of inflammatory and necrotic lesions in the liver, lymph nodes and spleen. Acute inflammatory lesions were also present in the lungs (pneumonia) and brain (very mild encephalitis). Molecular analyzes carried out by the laboratory of the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec revealed the presence of an AIV H5N1) in the brain. This result was confirmed by the Canadian Food Inspection Agency laboratory. The results of these tests indicate that this dolphin died as a result of an acute infection with an AIV H5N1 virus.
Although the H5N1 AIV viruses primarily affect birds, several mammalian species are also known to be susceptible. In marine mammals, infections with this virus have been documented mainly in common seals, but cases have also been reported in some gray seals. Until recently, no cases of fatal avian influenza virus infections had been documented in cetaceans (whales and dolphins). To our knowledge, only two cases of AIV H5N1 infection in cetaceans have been reported so far, one case in a bottlenose dolphin in Florida and one case in a harbor porpoise in Sweden. The case presented here, which would therefore be the first case of infection with this virus in a white-sided dolphin, indicates that this species is susceptible to this virus emerging in North America.
Data collected by the RQUMM does not appear to indicate an increase in white-sided dolphin mortality in the St. Lawrence Estuary this summer, despite the presence of an outbreak among common seals. This suggests that there has been no transmission of this virus between dolphins and therefore the number of cases should be limited; contact between dolphins and infected birds is probably rare.
Although the risk of transmission of this flu virus to humans and pets seems low, it is recommended not to approach, and above all not to touch, sick or dead marine mammals. Contact between our pets and dead wild animals should also be avoided.
Stéphane Lair – CWHC Quebec / CQSAS, Faculty of Veterinary Medicine, University of Montreal
