HPAI: What are the effects of highly pathogenic avian influenza on canids?

On March 29, 2022, a large-scale die-off of crows in a public park in Sapporo, in northern Japan, caught the attention of scientists, especially since a red fox and a Japanese raccoon dog also fell victim to the outbreak. What happened?   Cases of humans infected with the HPAI H5N1 virus are extremely rare. The systematic culling of infected flocks has, for the time being, helped limit outbreaks worldwide. However, surveillance data from 2021–2022 revealed an unprecedented spread of the virus among the avifauna on nearly every continent. The epidemiological investigation and microbiological tests on the three species established that it was highly likely that the fox dog and the raccoon dog were infected with the HPAI virus through contact with sick crows, with one caveat: the routes of transmission were different, resulting in differing disease outcomes in the two canid species involved. Analysis of these HPAI viruses showed that the three sources were ultimately closely linked to one another. Crows are, in fact, more susceptible to the current strain, which would explain the number of cases in the study. The necropsy of the canids revealed that the HPAI virus had infected their upper respiratory tracts as well as the fox’s brain, a finding previously reported in other studies. As for the raccoon dog, even though it survived the acute infection, the virus caused severe damage to its eyes. The study of influenza virus cell receptors in its respiratory system also suggests that this species may be susceptible to infection by the HPAI virus. A more in-depth analysis revealed that the viruses from the three sources were closely related to one another, although they were not completely identical. In this case in Japan, it is highly likely that H5N1 infected a group of crows, causing mass mortality among these birds, before spreading to the red fox through the consumption of crow carcasses. As for the raccoon dog, close contact with the carcasses would have been sufficient to infect it. It should be noted that several infections in wild carnivorous mammals have been reported over the past several months. Cases in domestic carnivores have also been reported. There is an urgent need to implement wildlife surveillance to better understand the virus’s ecology and the risk factors for its spread in the wild.   News update on January 3, 2023: A cat infected with the highly pathogenic avian influenza virus A(H5N1) in France

ANSES: Avian Influenza in 6 Questions