Avian Influenza in Indoor Cats: A New Concern for Veterinary Medicine
A recent CDC report has confirmed that two indoor pet cats in Michigan developed severe neurological signs and died from highly pathogenic avian influenza (H5N1). These cases are the first known instances of strictly indoor cats becoming infected without direct exposure to affected poultry or dairy farms, raising concerns about alternative transmission routes.
Case Details
The two cats, a 5-year-old domestic shorthair and a 6-month-old Maine Coon, belonged to dairy farmworkers but lived exclusively indoors. Both cats developed progressive neurological signs, facial swelling, anorexia, and ataxia, with rapid clinical decline. Despite supportive care, both died or were euthanized within days.
Genetic sequencing confirmed the virus strain was clade 2.3.4.4b, genotype B3.13, the same circulating in dairy cattle across multiple states.
Potential Transmission and Occupational Risks
While previous feline H5N1 cases have been linked to ingestion of infected birds or raw pet food, these cats had no known direct contact with infected livestock. The owners, however, worked closely with H5N1-positive dairy cattle and may have brought the virus home through contaminated clothing, footwear, or unpasteurized milk.
Neither farmworker wore personal protective equipment (PPE) on the job, and both declined testing for influenza A. One had been splashed in the eyes with unpasteurized milk shortly before their cat’s illness.
Additionally, 24 veterinary staff members were exposed to the sick cats, with seven reporting symptoms such as nasal congestion and headaches. Those tested were negative for influenza A, but the incident highlights the importance of infection control protocols in veterinary settings.
Key Considerations for Veterinarians
These cases underscore the need for vigilance in veterinary practice, particularly when evaluating cats with neurological or respiratory signs in regions affected by H5N1 outbreaks.
Consider PPE use when handling ill cats in potential outbreak areas.
Obtain occupational histories from pet owners to assess risk of exposure.
Educate farmworker clients on biosecurity measures, including changing clothing and footwear before entering the home.
Avoid raw pet food diets, which have previously been linked to H5N1 transmission in cats.
Monitor evolving H5N1 research on fomite and environmental transmission risks.
The exact mode of transmission in these cases remains uncertain, but the findings suggest that fomite transmission or exposure to contaminated dairy products could be a viable route for H5N1 infection in pets. Given the ongoing outbreaks in dairy cattle, poultry, and wildlife, continued research and strict biosecurity measures are critical to preventing further spread.
