Cats big or small can become infected with the new coronavirus but dogs appear not to be vulnerable, according to a study published Wednesday, prompting the World Health Organization (WHO) to say it will take a closer look at the transmission of the virus between humans and pets.
The study, published on the website of the journal Science on Wednesday, found that ferrets can also become infected with SARS-CoV-2, the scientific term for the virus that causes the COVID-19 disease.
Dogs, chickens, pigs and ducks are not likely to catch the virus, however, the researchers found.
The study was aimed at identifying which animals are vulnerable to the virus so they can be used to test experimental vaccines to fight the COVID-19 pandemic, which has killed more than 83,000 people worldwide since it emerged in China in December.
SARS-CoV-2 is believed to have spread from bats to humans. Except for a few reported infections in cats and dogs, there has not been strong evidence that pets can be carriers.
A tiger at the Bronx Zoo in New York City who developed a dry cough and loss of appetite after contact with an infected zookeeper tested positive for the coronavirus Sunday.
The study, based on research conducted in China in January and February, found cats and ferrets highly susceptible to the virus when researchers attempted to infect the animals by introducing viral particles via the nose.
They also found cats can infect each other via respiratory droplets. Infected cats had the virus in the mouth, nose and small intestine. Kittens exposed to the virus had massive lesions in their lungs, nose and throat.
"Surveillance for SARS-CoV-2 in cats should be considered as an adjunct to the elimination of COVID-19 in humans," the authors wrote.
In ferrets, the virus was found in the upper respiratory tract but did not cause severe disease.
Antibody tests showed dogs were less likely to catch the virus, while inoculated pigs, chickens and ducks were not found to have any strain of the virus.
"It's both interesting and not terribly surprising in the sense that with the original SARS epidemic, civet cats were implicated as one of the vectors that may have transmitted virus to humans," said Daniel Kuritzkes, head of infectious diseases at Boston's Brigham and Women's Hospital.
"What these data do provide is support for the recommendation that people who are with COVID-19 should be distancing themselves, not only from other household members but also from their household pets, so as not to transmit the virus to their pets, particularly to cats or other felines," he said.
"If somebody has been diagnosed with COVID-19 in a household, or they have been exposed to someone who was and are in quarantine, they should treat their pet just like any other human in their family," said Dr. Rustin Moore, the dean of Ohio State University's College of Veterinary Medicine.
He added, "that means maintaining social distancing, no touching, petting, cuddling, or hugging."
The WHO said Wednesday it is working with its partners to look more closely at the role of pets in the health crisis.
Based on the evidence so far, WHO epidemiologist Maria Van Kerkhove told a news conference, "We don't believe that they are playing a role in transmission but we think that they may be able to be infected from an infected person."
The WHO's top emergencies expert Mike Ryan asked people not to retaliate against animals over the outbreak.
"They're beings in their own right and they deserve to be treated with kindness and respect. They are victims like the rest of us," he said.