Beyond Birds: Wildlife Rehabilitators Discover Spread of Avian Influenza to Small Mammals

By Barbara Hyde-Lay

1 August 2023


Reed fox walks with bird prey in the mouth

Just like people, birds can get the flu.  And — also just like people — birds that are in close contact with other birds can pass along the virus.

Avian Influenza A viruses (IVAs) are responsible for causing flu in wild migratory birds. Currently, the main concern with IVAs in wild birds is that they can spread the diseases to domesticated birds, such as poultry, rapidly causing widespread sickness and death. 

To complicate matters, Dr. Sherri Cox, a wildlife biologist in the Department of Integrative Biology, has recently seen a new and alarming trend with IVAs.

With a research program focused on wildlife health and rehabilitation, Cox is frequently in the field working with wildlife rehabilitators across Canada to help with the recovery of sick and injured wildlife until they can be released into the wild again.

While out in the field, Cox and collaborators discovered that IVAs were not just being passed along to other birds but also to mesocarnivores —small mammals such as skunks, foxes, and minks that are not strictly carnivorous in terms of what they eat.  

“Mesocarnivores mostly eat a diet of meat as well as non-vertebrate foods,” explains Cox.

IVAs had never been seen before in these animals, so Cox and her colleagues set out to find what this meant for Canadian wildlife.

“The mesocarnivores had the same IVA strains that wild birds from Europe carried over into our local bird populations in 2021 and 2022, and researchers were already studying the effect of these viruses in birds. However, there was nothing documented about the virus in mammals, including how it presented and what the effects were,” Cox says.

For example, the team found that a number of baby foxes (called ‘kits’) presented with devastating neurological symptoms including tremors and seizures, which was similar to how birds with IVAs presented.

“By reaching out to our rehabilitation partners in Ontario and other provinces, we found that a number of mesocarnivores were being infected by the virus, so the cases we had observed were not isolated,” notes Cox.

The researchers hypothesize that the virus is spread to foxes and other mesocarnivores via their food. For example, a ‘mama’ fox will bring home an infected bird for dinner, and the virus then infects the kits after consumption. Interestingly, infected kits do not appear to transmit the virus to siblings or other non-infected family members.

Fortunately, the virus is much less deadly in mesocarnivores than in birds. The researchers found that mesocarnivores recover and develop antibodies against IVAs, a promising discovery for the future prevention and treatment of mesocarnivores and other Canadian wildlife affected by these viruses.

The cross-Canada study highlights the importance of wildlife rehabilitators when it comes to identifying and monitoring wildlife diseases that can also impact human health.

“This type of research is important because it really shows the role of wildlife rehabilitators from a ‘One Health’ perspective. They’re working front line with sick and injured wildlife, such as these mesocarnivores, so they’re playing a critical role in helping animals while also protecting humans from pathogens such as IVAs,” says Cox.

This study was funded by the Canadian Food Inspection Agency emergency funding for 2022 AIV outbreaks.


Read the full study in Emerging Microbes & Infections.

Read about other CBS Research Highlights.