Cats were susceptible to COVID-19 coronavirus, while the virus replicated poorly in dogs, Chinese researchers said.
Felines also appear to be able to pass the virus to each other through respiratory transmission, Zhigao Bu, PhD, of Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences in Harbin, China, and colleagues wrote in .
SARS-CoV-2 is thought to have originated from a bat, though intermediate animal sources of the virus remain a mystery, they said.
In addition to detecting animals that could become reservoirs of infection, the types of susceptible animals have implications for drug and vaccine development, namely "which animal(s) can be used most precisely to model the efficacy of such control measures in humans." Not to mention "cats and dogs are in close contact with humans."
After intranasally inoculating ferrets with SARS-CoV-2, the authors found the virus "can replicate in the upper respiratory tract of ferrets for three to eight days without causing severe disease or death." The virus may replicate in the digestive tract, but not the lung lobes, they added.
They then turned their attention to cats and dogs. Researchers intranasally inoculated cats, ages 6 to 9 months and, to monitor respiratory droplet transmission, they placed an uninfected cat in a cage adjacent to each of the three infected cats. They collected feces from the cats and checked for viral RNA in their organs after euthanasia "to avoid injury," as the cats were aggressive, researchers said.
The authors found viral RNA in the soft palate and tonsils of both a virus-inoculated cat and an exposed cat with viral RNA-positive feces. The exposed cat also had viral RNA in its nasal turbinate and trachea, "indicating that respiratory droplet transmission had occurred in this pair of cats," the authors wrote.
Researchers replicated the study in even younger cats and found "massive lesions in the nasal and tracheal mucosa epitheliums, and lungs," concluding 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 the airborne route."
Examining dogs, they intranasally inoculated five 3-month-old beagles and put them with two uninoculated beagles. Viral RNA was detected via rectal swab of two virus-inoculated dogs on day 2 and one on day 6. However, "infectious virus was not detected in any swabs collected from these dogs," they said.
On day 14, researchers collected sera from all the dogs. Two virus-inoculated dogs seroconverted, while the other dogs and the two exposed dogs were all seronegative for SARS-CoV-2, indicating their "low susceptibility" to the virus.
Similar studies were conducted in pigs, chickens, and ducks, and no viral RNA was detected in any virus-inoculated animals or exposed animals, they said.
They offered an explanation for their findings, saying cats and ferrets only have two amino acid differences in SARS-CoV-2 spike-contacting regions of angiotensin-converting enzyme 2 (ACE2), the receptor SARS-CoV-2 uses to enter cells.
While researchers concluded ferrets would be a "candidate animal model" for drug or vaccine candidates, they suggested surveilling cats as an adjunct to the elimination of COVID-19 in humans, as cats in Wuhan have been found to be seropositive for the virus.
Disclosures
Bu and co-authors disclosed no relevant relationships with industry.
Primary Source
Science
Shi J, et al "Susceptibility of ferrets, cats, dogs, and other domesticated animals to SARS–coronavirus 2" Science 2020; DOI: 10.1126/science.abb7015.