People Can Spread Bird Flu to Their Cats, Study Suggests

Two indoor cats in the same county in Michigan were infected with H5N1 avian flu last May, likely via their owners who worked on dairy farms.

Both cats had severe respiratory and neurologic illness and died, reported Ramya Naraharisetti, PhD, of CDC’s Epidemic Intelligence Service and the Michigan Department of Health and Human Services, and colleagues in Morbidity & Mortality Weekly Report (MMWR). The cats also both tested positive for the B3.13 genotype of H5N1 bird flu, the predominant strain in dairy cattle.

“Further research is necessary to evaluate the risk of fomite transmission and other types of transmission routes of [highly pathogenic avian influenza] A(H5N1) virus to cats,” Naraharisetti and colleagues wrote.

They also recommended that given the potential for fomite contamination, farm workers should remove their shoes and clothing for cleaning before entering their homes, and veterinarians evaluating cats who may have been exposed to H5N1 should wear personal protective equipment (PPE) — as should dairy farm workers.

The findings were reportedly originally slated to be published in the Jan. 23 issue of MMWR that was not published due to a Trump administration halt on communications.

The index cat was 5 years old, and one of three in its household; all were indoor-only cats. It developed a decreased appetite, lack of grooming, disorientation, and lethargy, followed by progressive neurologic deterioration, the researchers reported.

Its owner took it to the vet on the second day of its illness; by day 4, it was referred to a tertiary care center at Michigan State University where it was euthanized.

Brain and nasal swabs taken as part of a necropsy were positive for H5N1 on PCR, specifically the B3.13 genotype.

One of the other cats in the home also became sick, but recovered after 11 days and was never tested for influenza. The third cat had no signs of illness, the researchers said.

While the farm worker was never tested for influenza, this person did report a day of vomiting and diarrhea before the first cat got sick. One of the two adolescents in the home also reported a cough, sore throat, headache, and myalgia 6 days after the first cat got sick.

Just under a week after the first cat got sick, another indoor-only cat, age 6 months, was brought to the tertiary care clinic with a 1-day history of progressive neurologic deterioration, anorexia, lethargy, and facial swelling. It died within 24 hours of the onset of illness, the researchers said.

Nasal swabs were positive for the B3.13 genotype of H5N1, they noted. The other cat in that household never became sick.

The cats’ owner worked on a dairy farm and reported not wearing PPE while handling raw milk, and reported frequent milk splash exposures to the face, eyes, and clothing. This person also did not remove work clothes before coming into the home, and said the cat that became ill would roll around in those work clothes, while the other cat would not.

This owner was not tested for influenza, but had eye irritation 2 days before the cat got sick, researchers reported.

Researchers cautioned that because neither farm worker was tested for influenza, it’s not known if their gastrointestinal and ocular symptoms, respectively, were due to H5N1.

Nonetheless, the researchers urged farm workers to be cautious about potentially spreading the infection to their cats, and also noted that “cats might pose a risk for human infection” — but this would need further investigation.

None of the veterinary workers involved in the cases tested positive for influenza A.

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