Severe Acute Respiratory Syndrome Coronavirus 2-Specific Antibodies in Pets in Wuhan, China.

Dear Editor,

In this Journal, Hogan et al. have reported the household pet dogs and cats play important role in colonization of methicillin-resistant Staphylococcus aureus (MRSA). We would like to share our findings for infection of SARS-CoV-2 in household pet cats and dogs. In December 2019, cases of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), were first reported in Wuhan, China.2, 3, 4 Since then, a large number of human COVID-19 cases have been reported around the world, becoming a global pandemic as declared by the World Health Organization (WHO). Experimental data has confirmed that the SARS-CoV-2 virus can use angiotensin-converting enzyme II (ACE2) as a receptor. Furthermore, animal models of SARS-CoV-2 infection have shown that ferrets and cats are susceptible to infection, implying that companion animals might be infected after contact with individuals carrying COVID-19. In this study, we collected swab and blood samples from pet cats and dogs in Wuhan whose owners were confirmed to have COVID-19. Our results provide serological evidence for SARS-CoV-2 infection in pets.

Pet cats and dogs were recruited from COVID-19 patients admitted to Wuhan Jinyintan Hospital, one of the designated hospitals for COVID-19. Participation of each pet was granted by the verbal informed consent of the respective owner. Sampling was conducted on 30 and 31 March 2020. Whole blood, oral, and rectal swabs were collected, and the sex and age of the pets were recorded. Swab samples were collected using sterile swabs and placed in a vial containing 2 ml of viral transport medium, stored at 2–8 °C, and shipped to the laboratory within 12 h for further analysis. Whole blood samples (0.5–1 ml) were drawn into evacuated tubes containing EDTA. Plasma was separated, aliquoted, and stored at −40 °C prior to processing.

Swab and whole blood samples were collected from 10 cats (four female, six male) and 9 dogs (four female, five male) (Supplementary Table 1) from 15 owners infected with COVID-19, from 15 communities located in six districts in Wuhan (Supplementary Figure 1). The mean ages of enroled cats and dogs were 1.83 years (range: 0.4 to 4.6 years, median 1.7 years) and 3.07 years (range: 0.9 to 7.4 years, median 2.3 years), respectively. All cats and dogs were physically normal when sampled. Swab samples were tested for SARS-CoV-2 RNA using real-time reverse transcription polymerase chain reaction (rRT-PCR), with primers and probes targeting the nucleocapsid protein (N) and RNA-dependant RNA polymerase (RdRp) genes of SARS-CoV-2. All pet samples were negative for SARS-CoV-2 RNA for both N and RdRp genes. The internal reference gene GADPH was amplified in all samples (data not shown). Titres of SARS-CoV-2 S1-specific IgG in plasma were determined with double antigen sandwich enzyme-linked immunosorbent assay (ELISA), as described previously. Two cats (cat 8 and 18) and one dog (dog 4) were strongly positive and showed high ELISA optical density (OD) ratios for IgG (Fig. 1 A). Positive plasma samples were further analysed with neutralising titres using the plaque reduction neutralisation test (PRNT) for SARS-CoV-2. Consistent with IgG titres, cat 8, cat 18, and dog 4 showed neutralising titres of 1:240, 1:240 and 1:120, respectively (Fig. 1B). Several other pet plasma samples were tested in parallel and showed titres of less than 1:20 (data not shown). The serological data indicates that some of the pets had been infected with SARS-CoV-2.

Fig. 1

SARS-CoV-2-specific antibodies in pet cats and dogs in Wuhan. (A) Titres of SARS-CoV-2 S1-specific IgG in plasma were determined with double antigen sandwich ELISA. OD ratio, optical density at 450–630 nm. Y-axes on the right and left indicate ELISA OD ratios for pet cats and dogs, respectively. N.C. and P.C. represent negative and positive controls, respectively. (B) Neutralising titres for SARS-CoV-2 in two cats and one dog that tested positive by sandwich ELISA. Neutralisation titres were defined as the serum dilution resulting in a plaque reduction of at least 50%. X-axis indicates the pet number. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

We then conducted telephone questionnaires with the owners of the three pets. All owners and their spouses were diagnosed with COVID-19. All three pets were in close contact with the owners and their spouses when they developed COVID-19 symptoms. During the period when the owners were admitted to hospital, cat 8 left the house and wandered outside for more than 1 month; dog 4 was fostered by a pet hospital for more than 1 month until the owner was discharged and back home; and cat 18 was quarantined at home with cat 17 and dog 16, and cared for by other family members once every 3 days; cat 17 and dog 16 tested negative for SARS-CoV-2 antibodies. Questionnaire data suggests that pets acquired SARS-CoV-2 virus from their owners, while other source of infection could not be excluded.

In this study, we conducted a survey for SARS-CoV-2 in pets whose owners were diagnosed with COVID-19, in 15 communities in Wuhan. Serological data suggests that three pets (two cats, one dog) had been exposed to the virus, although viral RNA detection was negative. Prior to our study, a preprint of a research article posted online at bioRxiv indicated that SARS-CoV-2-specific antibodies were detected in cats in Wuhan at the time of the COVID-19 epidemic. In addition, pet dogs and cats in Hong Kong, whose owners had been diagnosed with COVID-19, tested positive for SARS-CoV-2 RNA. Collectively, these results indicate the SARS-CoV-2 can be transmitted to companion animals, possible through contact with owners carrying COVID-19. However, we were not able to determine whether, under natural conditions, pet cats and dogs can be readily infected with or transmit SARS-CoV-2. Further studies will be needed to establish the role of pets in the current COVID-19 epidemic.

Declaration of Competing Interest

None