Cats and dogs are in close contact with humans, and therefore it is important to understand their susceptibility to SARS-CoV-2 for COVID-19 control. We first investigated the replication of SARS-CoV-2 in cats. Five 8-month-old outbred domestic cats (referred to here as “subadult cats”) were intranasally inoculated with 105 pfu of CTan-H. Two of the subadult cats were scheduled to be euthanized on day 6 p.i. to evaluate viral replication in their organs. Three subadult cats were placed in separate cages within an isolator. To monitor respiratory droplet transmission, an uninfected cat was placed in a cage adjacent to each of the infected cats. It was difficult to perform regular nasal wash collection on the subadult cats because they were aggressive. To avoid possible injury, we only collected feces from these cats and checked for viral RNA in their organs after euthanasia.
From the two subadult cats that were euthanized on day 6 p.i. with CTan-H, viral RNA was detected in the nasal turbinates, soft palates, and tonsils of both animals, in the trachea of one animal, and in the small intestine of the other; however, viral RNA was not detected in any of the lung samples from either of these animals (Fig. 2A). Infectious virus was detected in the viral RNA-positive nasal turbinates, soft palates, tonsils, and trachea of these cats, but was not recovered from the viral RNApositive small intestine (Fig. 2B).
In the transmission study, viral RNA was detected in the feces of two virus-inoculated subadult cats on day 3 p.i., and in all three virus-inoculated subadult cats on day 5 p.i. (Fig. 3A). Viral RNA was detected in the feces of one exposed cat on day 3 p.i. (Fig. 3A). The subadult cats with viral RNA-positive feces were euthanized on day 11 p.i., and viral RNA was detected in the soft palate and tonsils of the virusinoculated animal and in the nasal turbinate, soft palate, tonsils, and trachea of the exposed animal (Fig. 3B), indicating that respiratory droplet transmission had occurred in this pair of cats. We euthanized the other pairs of animals on day 12 p.i., and viral RNA was detected in the tonsils of one virus-inoculated subadult cat, in the nasal turbinate, soft palate, tonsils, and trachea of the other virus-inoculated author/funder. It is made available under a CC-BY-NC-ND 4.0 International license. bioRxiv preprint doi:
https://doi.org/10.1101/2020.03.30.015347. The copyright holder for this preprint (which was not peer-reviewed) is the 6 subadult cat, but was not detected in any organs or tissues of the two exposed subadult cats (Fig. 3B). Antibodies against SARS-CoV-2 were detected in all three virus-inoculated subadult cats and one exposed cat by use of an ELISA and neutralization assay (Fig. 3C, D).
We replicated the replication and transmission studies in juvenile cats (aged 70–100 days) (Fig. 2CF and Fig. 3E-G). Histopathologic studies performed on samples from the virus-inoculated juvenile cats that died or euthanized on day 3 p.i. revealed massive lesions in the nasal and tracheal mucosa epitheliums, and lungs of both cats (fig. S5). These results indicate that SARS-CoV-2 can replicate efficiently in cats, with younger cats being more permissive and, perhaps more importantly,
the virus can transmit between cats via respiratory droplets.
