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A pre-print paper has raised concerns about the potential role of cats in the spread of avian influenza, highlighting the need for increased surveillance of the virus in felines
Since May 2022, the increasing spread of High Pathogenic Avian Influenza (HPAI), also known as avian flu H5, has infected up to 23 mammal species. According to the US Department of Agriculture, 374 animals have been infected, resulting in illness, severe disease and even death in some cases.
The avian flu has infected 97 red foxes, 82 house mice, 43 skunks and 36 domestic cats. Infections have also been reported in mountain lions (22 cases), harbour seal (21 cases) and skunk (43 cases). Other species that have been impacted are raccoon, deer mouse and bobcats among others.
However, the spread of disease among domestic cats is becoming a cause of concern. A recent paper examining the spread of avian flu among cats over the last 20 years found the latest strain of H5N1 (clade 2.3.4.4b) poses increased risks.
A pre-print study Avian Influenza Virus Infections in Felines: A Systematic Review of Two Decades of Literature stated that given the emerging threat of a human pandemic caused by avian influenza, infections in felines or cats that are susceptible to avian flu virus infection must be closely monitored among other mammals.
The World Health Organization (WHO) has recently added avian flu (influenza A virus) to its list of priority pathogens that could potentially trigger the next pandemic.
The pre-print paper explained that felines feed on dead wild birds and hence “may serve as a host for avian influenza virus adaptation to mammals.”
Previous studies have shown feline-to-feline experimental transmission. “Domestic cats are a popular human companion animal and thus provide a potential pathway for zoonotic spillover of avian influenza viruses to humans,” the paper stated.
From 2004 to 2024, the highest number of infections in domestic cats was reported in 2023. The rise in infection cases coincided with the latest clade spreading among mammals.
The study discovered that the current strain of H5N1 caused a 67 per cent fatality rate and that cats were also susceptible to infection from other cats. Over a 20-year period, the researchers investigated approximately 486 avian flu virus infections in felines and discovered 249 deaths from the disease.
The researchers also noted infections in 12 feline species across seven geographical regions and 17 countries, with Asia, including Southeast Asia, reporting the highest rate of infection (54 per cent). Europe and North America reported 24 per cent and 12 per cent, respectively.
Apart from the US, feline infections of H5N1 clade 2.3.4.4b have also been reported from Finland, Italy, France, Peru, Poland and South Korea, including domestic cats, bobcats, lynx, lion and caracals.
Though the majority of the cases involved bird-to-feline infection because the animals were fed dead pigeons, chickens and other birds, three cases involved feline-to-feline infection and two cases involved infection from cattle because they were fed raw milk and colostrum.
The US Centers for Disease Control and Prevention has classified the risk to humans as low because no reports of the virus infecting humans have surfaced. Since March earlier this year, 13 humans from three states have reported infections in the US, including 189 dairy herds in 13 states.
According to a study published in journal Nature in July 2024, the cases highlight the zoonotic potential of the virus, underscoring the need for robust measures to prevent and control the infection and further spread of H5N1 in dairy cattle.
