Late last year, when the UK’s coronavirus was on the rise, Dr. Luca Ferasin and colleagues reported an increase in patients with symptoms of myocarditis or inflammation of the heart.
The condition is a rare side effect of the mRNA Covid-19 vaccines, most common in men under 30. It can also be caused by infection with the virus itself.
But these patients weren’t human; it was cats and dogs.
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“These were dogs and cats that were depressed, lethargic and lost appetite,” said Ferasin, a veterinary cardiologist at the Ralph Veterinary Referral Center in Buckinghamshire, England. “And they either had difficulty breathing because fluid had built up in their lungs from the heart disease, or they fainted from an underlying abnormal heart rhythm.”
Before December, about 1.5 percent of pets referred to The Ralph were diagnosed with myocarditis, he said. However, between December and March that number rose dramatically, rising to 12.5 percent of pets with confirmed myocarditis.
Ferasin and his colleagues later found that many of the pet owners had either tested positive for Covid or had symptoms of the disease within three to six weeks of their pets becoming ill. That information, coupled with the fact that the timing coincided with the surge in cases caused by the alpha variant of the virus in the UK, prompted researchers to test the pets for SARS-CoV-2.
Ferasin described the rise in cases of Covid-induced myocarditis in pets in a report published in Veterinary Record on Friday.
Out of 11 animals, two cats and one dog tested positive for the alpha variant of the virus, and two other cats and one additional dog tested positive for Covid antibodies. The remaining five animals tested negative for antibodies and the virus. None of the animals tested had symptoms of a respiratory infection or other typical signs of Covid, but all had myocarditis, Ferasin said.
Since The Ralph only sees heart patients, the researchers cannot say whether dogs and cats may develop typical Covid symptoms in other cases of infection.
It’s also unknown if general practice veterinarians are seeing more cases of myocarditis caused by SARS-CoV-2, said Margaret Hosie, a veterinary virologist at the MRC-University of Glasgow Center for Virus Research.
But maybe that’s because these vets don’t know it’s a possibility, said Hosie, who wasn’t involved in the research. Reports like this one will help family doctors become aware of Covid-induced myocarditis in pets so they know they need to ask and test for Covid exposure.
All animals in this study recovered after supportive treatment with supplemental oxygen and diuretics to remove fluid from the lungs, with the exception of one cat with persistent cardiac arrhythmias, in which the owners decided to euthanize the animal. None of the animals were treated with antiviral drugs, Ferasin said.
There have been other cases where domestic cats and dogs around the world have tested positive for other variants of Covid, including the Delta variant, but so far there is no evidence that the other variants cause similar heart problems in pets. In addition, Ferasin said the rate of pets with myocarditis called The Ralph has returned to pre-Covid levels of 1 to 2 percent.
As a precaution, both Ferasin and Hosie advised pet owners with Covid to avoid contact with their pets, just as they would with other people.
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“If it is not possible to get someone else to take care of your pet, you should consider wearing a mask while preparing your food to minimize the chance of infection,” said Hosie.
Several studies so far show that the virus is transmitted from humans to cats and dogs, but not the other way around. “So, people shouldn’t panic” if their pets show signs of illness, Ferasin said.
So far, Covid does not seem to cause any serious problems in animals; most recover fairly quickly, said Hosie.
Nonetheless, it is important to study Covid in pets as it may be a reservoir of virus that allows the virus to mutate in ways that cause more serious diseases in humans, she added.
“Of course, right now, we are focused on preventing human-to-human transmission because that is critical,” she said. “But if we leave other species out of sight, we could run into problems in the future.”
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