Avian Influenza in Cats: What You Need to Know

An article from the Colorado Veterinary Medical Association (CVMA) reports that six cases of highly pathogenic avian influenza (HPAI) caused by the H5N1 virus were diagnosed in domestic cats in Colorado in 2024. What’s the story?   One of these cases was directly linked to an infected dairy farm. Of the six cases, two involved cats that lived exclusively indoors with no direct exposure to the influenza virus, while three were cats that lived both indoors and outdoors, hunting mice or small birds and spending time indoors with their owners. Clinical signs observed in five of the six cats included lethargy and loss of appetite, followed by progressive respiratory signs in some and neurological signs in most. Before diagnosing H5N1 infection, several animals were tested for rabies due to the similarity of the neurological symptoms. It is recommended to consider infection with the highly pathogenic H5N1 virus in domestic cats even when not all risk factors or clinical signs are present. The virus, which is currently widespread in Colorado, is primarily detected in domestic cattle from dairy herds, with circulation among nearby wild mammals and wild birds. It is important to note that strain B3.13 of the Eurasian clade 2.3.4.4b of the H5N1 virus is spreading among animals that were not historically considered animal reservoirs of the HPAI virus. To date, this viral lineage has not been detected in migratory waterfowl. An article published in Scientific American discusses avian influenza infection in domestic cats and the potential implications for human health. Since 2020, the highly pathogenic H5N1 strain of avian influenza has spread to a wider range of animals, including cats, which can potentially transmit the virus to humans. Domestic cats could act as vectors in this transmission, although the current risk remains low, according to the CDC. The article notes a significant increase in infections among domestic cats beginning in 2023, which coincides with the rapid spread of the current strain of H5N1 among mammals. The risk of infection is expected to increase for cat owners, veterinarians, and animal shelter employees if the virus continues to circulate unchecked. Precautions are recommended, such as avoiding feeding your cat raw meat or unpasteurized milk and limiting unsupervised outdoor time to prevent it from hunting and ingesting infected wild birds. The mortality rate among cats infected with the current strain of H5N1 is approximately 67%, which prompts owners to keep their cats indoors and away from wild birds. Cases of virus transmission between cats have been reported in shelters, and staff at these facilities have also contracted avian influenza from the cats in their care.  

Specific symptoms of avian influenza (H5N1 virus) in cats include:

• fever;
• lethargy;
• breathing difficulties;
• ataxia (loss of coordination);
• seizures;
• conjunctivitis;
• neurological signs;
• serous-bloody nasal discharge;
• bloody diarrhea;
• severe respiratory distress.

Some infected cats develop severe symptoms and may die quickly. In some cases, cats remain asymptomatic for up to 24 hours before they die.    

What are the risks to other pets?

The risks to other pets when a cat is infected with avian influenza (H5N1) appear to be limited. Transmission between cats is possible, but there is no significant evidence of transmission to other domestic animal species. Cats can potentially transmit the virus through direct contact (petting, rubbing) or through the air (sneezing). However, the risk of virus transmission between cats or to other pets remains low, and transmission of the virus to humans via cats has not been demonstrated. Health authorities nevertheless recommend taking precautions, such as avoiding feeding animals raw meat and limiting interactions with potentially infected wild birds. Although transmission between cats remains possible, the risk to other pets is considered low.  

Transmission of avian influenza (H5N1) among pets through indirect contact is possible.

Transmission of avian influenza (H5N1) among pets through indirect contact is possible, although the risk is generally higher through direct contact. Animals can become infected through exposure to heavily contaminated environments, such as areas where infected birds congregate, or by ingesting food or water contaminated with feces from infected birds. Cats, for example, can contract the virus by drinking water containing viral biofilms or by consuming contaminated prey. However, indirect transmission between pets remains less well documented and is generally considered less likely than direct transmission.  

To protect pets from avian influenza, here are some practical tips.

 

5. Limit outdoor exposure: Keep your pets, such as cats and dogs, indoors to prevent them from hunting or eating potentially infected wild birds.
6. Monitoring and reporting: If your pet comes into contact with a sick or dead bird, report it to the local animal health authorities.
7. Strict hygiene: Wash your hands with warm water and soap after any contact with an animal, its feces, or its litter. Avoid letting your pets access potentially contaminated areas, such as outdoor toilets or water sources.
8. Veterinary consultation: If you have concerns about your pet’s health, consult a veterinarian for specific advice and appropriate preventive measures.
9. Avoid raw foods: Do not feed your pets raw meat or unpasteurized milk, as these could be sources of contamination.

  By following these precautions, you can reduce the risk of avian influenza infection in your pets.