The highly pathogenic H5N1 avian influenza virus is still present: Mass mortality of snow geese during fall migration in southern Quebec

Juvenile snow goose infected with a highly pathogenic H5N1 avian influenza virus. The bird is listless, easy to approach and has half-closed eyes.

At the end of November, more than fifty snow goose carcasses were observed on the shores of the Richelieu River in Saint-Jean-sur-le-Richelieu, Quebec. Several live birds showing neurological signs (half-closed eyes, head tremors and abnormal and/or repetitive movements, recumbency) were also observed. Similar episodes have also been documented at several sites in the southern region of Quebec used as migratory stopover sites by snow geese.

Postmortem examination of a subsample of these geese by CWHC-Quebec (CQSAS) revealed a resurgence of infections with the H5N1 avian influenza virus. Indeed, macroscopic and histological lesions highly characteristic of this viral infection have been observed in birds and preliminary molecular examinations indicate the presence of this virus in affected birds (to be confirmed by the CFIA).

Following a decrease in cases over the summer, it therefore seems that the H5N1 avian influenza virus is still quite prevalent in this region. Since unusual mortality was not reported in their Arctic nesting ground, it can be assumed that these geese became infected when they arrived at the migratory stopovers. It can be hypothesized that the virus was maintained in the environment by resident species known to be potentially asymptomatic carriers, such as mallard ducks. Although these fall episodes are not unexpected, their relatively high intensity could suggest an increase in the pathogenicity of viral strains present in southern Quebec, at least for snow geese. The aggregation of large numbers of geese on water bodies at these sites favours the transmission of the virus from one bird to another.

In addition to affecting wild birds, this virus is highly pathogenic in domestic poultry; a large number of mortalities has been documented in farmed birds since the arrival of this strain in North America. In the event of unusual mortality in a bird farm, it is essential to consult a veterinarian.

Although highly pathogenic in birds, this strain of influenza virus seems to be of low pathogenicity in people. Nevertheless, it is still recommended to follow certain basic measures in order to reduce the risk of exposure to avian influenza and other potential zoonotic agents. For example, avoid handling wild birds with bare hands, or if contact cannot be avoided, wear gloves and wash your hands with soap and hot water (or with a hydroalcoholic solution).

To report the presence of a dead or sick wild bird in the province of Quebec contact 1-877-346-6763 and avoid handling the bird while waiting for instructions.

For more information on the situation in Quebec, visit the following web pages:

https://www.quebec.ca/en/agriculture-environment-and-natural-resources/animal-health/animal-diseases/list-animal-diseases/avian-influenza

CWHC – Quebec / CQSAS