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SARS-CoV-2 neutralizing serum antibodies in cats: a serological investigation

Our take —

This study indicates the potential for cats to become infected with SARS-CoV-2 within human communities, confirming anecdotal reports of infected cats in New York.

Study design

Ecological

Study population and setting

The study population consisted of 102 cats in Wuhan, China sampled after the outbreak of COVID-19 in the human population. Additional samples from 39 cats from the same area collected before the outbreak between March and May 2019 were included for comparison. All cats were sampled from animal shelters or pet hospitals.

Summary of Main Findings

Serum samples from cats were tested for the presence of antibodies against the SARS-CoV-2 spike protein: 15/102 (14.7%) of cats sampled after the outbreak were positive, and all of the 39 cats sampled before the outbreak were negative. An additional test for antibodies capable of neutralizing SARS-CoV-2 in cell cultures showed that 11/15 (10.8%) of antibody-positive cats during the outbreak were positive based on the neutralization test. Three of the cats with the strongest antibody responses had owners who were COVID-19 patients. None of the tested samples showed cross-reactivity in the antibody assays to type I and II feline infectious peritonitis virus.

Study Strengths

Inclusion of a viral neutralization assay and Western blotting provide important validation of the enzyme-linked immunosorbent assay for SARS-CoV-2 antibodies, which can be challenging to interpret due to the lack of a set cutoff value for assessing positives.

Limitations

Although the authors did find positive cats in the study, the sample size was still small, and additional samples could produce divergent estimates of prevalence in the cat population. It is unclear how many of each type of cat was collected (stray versus owned versus shelter). Such data would be useful for assessing prevalence in groups of cats with different routes or intensity of exposure. There is no information on the age of the cats, which may influence susceptibility to infection. It is also unclear how cats that were not owned by a COVID-19 patient were exposed to the virus, especially those cats that were in pet hospitals and shelters with limited human contact. Thus, these results may not be applicable to other populations of cats with very different population structure and patterns of human-cat contact. Additionally, antibody prevalence cannot be used to infer when cats became infected, i.e., what is the period from exposure to infection to recovery. Additional experimental infection studies must be done to establish the course of SARS-CoV-2 in cats.

Value added

This study indicates the potential for cats to become infected with SARS-CoV-2 within human communities, confirming anecdotal reports of infected cats in New York.