A sick cat at the San Diego Humane Society. Cats and dogs containing the B.1.1.7 SARS-CoV-2 variant were found.
ARIANA DREHSLER / AFP via Getty Images
By David Grimm
ScienceThe COVID-19 reporting is supported by the Heising-Simons Foundation.
The variants of SARS-CoV-2 that keep popping up are not just a human problem. Two reports released this week found the first evidence that dogs and cats can become infected by B.1.1.7, a recent variant of the pandemic coronavirus that is more easily transmitted between humans and also appears more deadly. The finding is the first time that one of the most important variants has been seen outside humans.
B.1.1.7 was first identified in the UK and this is where some of the infected pets were found. British animals have contracted myocarditis – an inflammation of the heart tissue that can cause heart failure in severe cases. But the reports provide no evidence that the SARS-CoV-2 variant is responsible, nor that it is more transmissible or dangerous in animals. “This is an interesting hypothesis, but there is no evidence that the virus causes these problems,” said Scott Weese, a veterinarian at Ontario Veterinary College at the University of Guelph, which specializes in emerging infectious diseases.
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Since December 2020, scientists have identified several variants of concern that appear more communicable or may elude the immune response. B.1.351, for example, was first detected in South Africa, and a strain called P.1 was first found in Brazil. The B.1.1.7 variant attracted early attention due to its rapid rise in the UK; it now accounts for about 95% of all new infections there.
So far, the impact of these variants on pets has been unclear. Although there have now been more than 120 million cases of COVID-19 worldwide, only a handful of pets have tested positive for the original SARS-CoV-2 – probably because no one is testing it. Infected pets appear to have symptoms ranging from mild to non-existent, and infectious disease experts say that companion animals are likely to play little, if any, role in the spread of the coronavirus among humans.
The new variants could change the equation, says Eric Leroy, a virologist at the French National Research Institute for Sustainable Development who specializes in zoonotic diseases. In one of the new studies, he and colleagues analyzed pets admitted to the cardiology unit of the Ralph Veterinary Referral Center on the outskirts of London. The hospital noticed a sharp increase in the number of dogs and cats with myocarditis: from December 2020 to February, the incidence of the condition jumped from 1.4% to 12.8%.
This coincided with an increase in the B.1.1.7 variant in the United Kingdom. So the team looked at 11 pets: eight cats and three dogs. None of the animals had a previous history of heart disease, yet they all present with symptoms ranging from lethargy and loss of appetite to rapid breathing and fainting. Laboratory tests revealed heart disorders, including irregular heartbeat and fluid in the lungs, all of which are seen in COVID-19 in humans.
Seven of the animals received polymerase chain reaction tests, and three returned positive for SARS-CoV-2 – all with the B.1.1.7 variant, the team reported yesterday on the preprint server bioRxiv. SARS-CoV-2 antibody tests on four of the other animals picked up evidence that two of them were infected with the virus. Earlier this week, researchers from Texas A&M University detected the B.1.1.7 variant in a cat and a dog from the same house in the state of Brazos.
The owner of Texas was diagnosed with COVID-19, and owners of five of the 11 UK pets tested positive for SARS-CoV-2 – all before their animals developed symptoms. The pets in Texas showed no symptoms when tested, although both began sneezing a few weeks later. All the American and British animals have since recovered, although one of the British cats has fallen back and had to be killed.
Leroy says it is unclear whether B.1.1.7 is more transmissible than the original human-animal strain, or vice versa. It is ‘impossible to say’ that pets infected with B.1.1.7 could play a more serious role in the pandemic, he adds, but ‘this hypothesis needs to be seriously raised.’
Shelley Rankin, a microbiologist at the University of Pennsylvania School of Veterinary Medicine, points out that the researchers only showed a link between B.1.1.7 infection and myocarditis, and that they did not rule out other causes of the condition. . “There is no evidence that pets were sick because of the virus,” she says.
Essentially, it agrees that neither the findings in Texas nor the United Kingdom should sound the alarm about pets endangering their owners. “The risk of them being a source of infection remains very low,” he says. ‘If my dog had it, he probably got it from me. And I’m much more likely to infect my family and neighbors before he does. ”
Yet he says scientists and veterinarians should do studies on what role, if any, SARS-CoV-2 and its variants play in myocarditis among pets. There is evidence that the virus can cause the condition in humans, Weese says, so it’s worth investigating it with companion animals. “It may be true,” he says, “but there is no reason for people to wake up now.”