Recognition, Testing, and Management of Avian Influenza in Potentially Exposed Cats

May 30, 2024

Avian influenza A(H5N1) has been detected in cats on farms affected by an ongoing outbreak in dairy cows and backyard bird flocks. Since April 1, 2024, avian influenza A(H5N1) has been confirmed in Idaho dairy cows located on eight dairy farms, in Cassia, Jerome, and Minidoka counties, and in four backyard flocks in Cassia and Jerome counties. Nationally, two human cases have been detected in dairy workers, one each in  Texas and Michigan. Infections with avian influenza A(H5N1) virus belonging to Gs/GD lineage, clade 2.3.4.4b Eurasian-origin have been reported in birds in the United States since 2021. These viruses mainly infect and spread among wild migratory waterfowl and domestic poultry and infrequently affect mammals. Veterinarians are advised to consider avian influenza A(H5N1) in cats with respiratory, neurologic, or enteric signs that have potentially been exposed to the virus.

Avian influenza A(H5N1) in cats

Avian influenza A(H5N1) primarily affects birds but can also infect mammals. Exposure of cats to avian influenza A(H5N1) usually occurs through consuming infected birds or other animals, or being in environments contaminated with the virus. In the current outbreak, consumption of unpasteurized milk from infected cows is thought to be another possible route of exposure. Spread from mammal to mammal is thought to be rare. Cat-to-cat transmission through respiratory secretions has occurred experimentally. The incubation period is one to two days, with virus shedding in feces and nasal secretions. Nasal excretion starts about three days after infection and continues for four or more days. Clinical signs in infected cats range from mild to severe, including death. Subclinical infections can occur. Signs include listlessness, loss of appetite, severe depression, fever, and jaundice. Respiratory, neurologic, and enteric disease may be seen. Differential diagnosis should exclude more common feline viral and bacterial infections causing similar signs.

Testing cats for avian influenza A(H5N1) in Idaho 

Veterinarians interested in testing specimens from ill or dead cats potentially exposed to affected dairy cows or their unpasteurized milk or to backyard flocks affected by avian influenza must contact the local public health district (PHD) epidemiologist for prior approval to submit samples to the Idaho Bureau of Laboratories (IBL) for testing. A map of PHDs and their contact information is found here: https://healthandwelfare.idaho.gov/health-wellness/community-health/public-health-districts  

Once prior approval is obtained from the PHD, the veterinarian will be provided with the appropriate sample submission form. Appropriate samples include nasal or oropharyngeal swabs in viral transport media or necropsy tissues depending on the clinical presentation: brain for neurological presentations and lung for respiratory presentations. No transport media is necessary for tissues. Tissues should be frozen in a Whirl-Pak bag (or other sealed bag) and once approved for testing, sent to IBL on chill packs in a leak-proof container. Ask the PHD about the availability of a courier.  

Samples must be accompanied by the appropriate sample submission form. If the animal has neurologic signs, rabies testing will be done on the brain prior to influenza testing.Testing will not be performed over the weekend. See https://statelab.idaho.gov for details and contact the IBL virology section, 208-334-0523 if you have questions. With prior approval, there is no charge for testing of cats if influenza A(H5N1) is suspected. Testing of specimens not approved for testing at IBL, and testing of veterinary patient specimens is available through the Washington Animal Disease Diagnostic Laboratory. Veterinarians who suspect HPAI A(H5N1) in livestock or poultry should contact the Idaho State Department of Agriculture, Animal Industries, at 208-332-8540.

Management of avian influenza A in cats 

All cats with suspected avian influenza disease should be kept in strict isolation. Treatment is supportive and symptomatic. 

Human infections with the circulating strain of HPAI A(H5N1) can result in asymptomatic or mild infection to severe illness and death. To reduce the risk of transmission of avian influenza A(H5N1) to veterinary staff from sick cats which might have been exposed to avian influenza A(H5N1): 

• Avoid unprotected direct physical contact or indirect contact with the animal.
• Wear PPE when handling the animal or cleaning the animal’s cage. 
• Safety goggles that fit snuggly (unvented or indirectly vented) or face shield, 
• An N95^® respirator,  
• Disposable gloves, 
• Coveralls or other protective clothing such as a surgical gown that is disposable and fluid-resistant, 
• Disposable boot covers or boots that can be sanitized, and 
• Head cover or hair cover that is disposable. 
• Use particular care during aerosol-generating procedures.  
• Use an EPA-registered antimicrobial product effective against avian influenza. 

Talk to your healthcare provider if you become ill with new respiratory symptoms, including conjunctivitis, after working with animals suspected or confirmed with avian influenza A. See https://www.cdc.gov/flu/avianflu/avian-in-humans.htm.  

Review the following CDC guidance documents: 

• Consideration for Veterinarians: Evaluating and Handling of Cats Potentially Exposed to Highly Pathogenic Avian Influenza A(H5N1) Virus: https://www.cdc.gov/flu/avianflu/veterinarians-handling-cats.htm  
• Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations: https://www.cdc.gov/flu/avianflu/hpai/hpai-interim-recommendations.html  

Additional resources 

• European Advisory Board on Cat Diseases: Guideline for influenza virus infections in cats. https://www.abcdcatsvets.org/guideline-for-influenza-virus-infections-in-cats/ 
• Influenza Virus Infections in Cats. Frymus T, Belák S, Egberink H, et al. Viruses. 2021;13(8):1435. doi:10.3390/v13081435  
• CDC: H5N1 Bird Flu: Current Situation Summary. https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm  
• USDA: Highly Pathogenic Avian Influenza (HPAI) Detections in Livestock. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock 
• USDA: Detections of Highly Pathogenic Avian Influenza in Wild Birds. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/wild-birds  
• ISDA: Highly Pathogenic Avian influenza in Detected in Idaho Cattle. https://agri.idaho.gov/main/animals/hpai/  
• ISDA: Avian Influenza Resources [domestic birds] https://agri.idaho.gov/animals/animal-disease/avian-influenza/  

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