In a perplexing development, several indoor house cats in Colorado have succumbed to bird flu, despite never venturing outside their homes. This unusual outbreak of H5N1 avian influenza has triggered a race among scientists to determine how these cats, which had no direct contact with the outdoors, contracted the virus.
The United States is currently grappling with a widespread H5N1 outbreak that has impacted nearly 200 dairy herds. Since March, at least 13 U.S. farm workers have also been infected, with over half of these cases occurring in Colorado. The virus has been documented in a variety of smaller mammals, including skunks, foxes, hedgehogs, sea lions, and even a polar bear. However, the recent infections among at least six cats, including two that lived entirely indoors, have raised significant concerns about the transmission pathways of the virus between species.
H5N1 is known to cause severe illness in cats, with symptoms mirroring those of rabies, including blindness, disorientation, paralysis, respiratory distress, and bloody diarrhea before leading to death. Despite the high viral load in Colorado, the transmission route to indoor cats remains unclear.
Dr. Rick Bright, an influenza and immunology expert, highlighted the mystery: “This situation raises many questions about how the virus reached these indoor environments. Potential sources include contaminated raw milk or food products, or the virus being transported into homes by people who might be infected or have come into contact with the virus through their clothing or footwear.”
Dr. Scott Weese, an infectious disease veterinarian, offered several theories, though none are entirely satisfying. One theory suggests that the cats might have been exposed to infected mice within the home. “Mice can carry the virus, but this is more likely in homes near poultry or dairy farms with active infections since mice have limited range,” Dr. Weese noted. “Birds might occasionally enter homes, and the consumption of raw meat could also be a transmission route, as seen in some other countries.”
In recent cases from Poland and South Korea, cat deaths were linked to the consumption of raw food contaminated with the H5N1 virus. In Poland, the virus was traced to raw cat food, while in South Korea, infected duck in cat food was identified as the source.
For the six cats in Colorado, three had some outdoor access, likely contracting the virus from hunting infected rodents or birds. The sixth cat, living on a farm, may have become infected through consuming contaminated milk.
Krutika Kuppalli, spokesperson for the Infectious Disease Society of America and a former WHO medical officer, emphasized the need for further investigation: “We need to explore all possible transmission routes and gather more information. Questions like whether these households had other animals or if any people living there have been infected need to be addressed.”
Colorado health officials have responded by urging veterinarians to consider H5N1 as a potential cause in ill cats, even if they have not had direct contact with farms, given the high prevalence of the virus in the state.
The situation underscores the urgent need for enhanced surveillance and information sharing to better understand and control the spread of H5N1 among diverse species.
Related Topics
How Do I Choose The Right Cat Sitter?
