Virus World

Three domestic cats in the U.S. – two in Nebraska and one in Wyoming – have recently tested positive for H5N1 avian influenza after eating wild birds, scientists say. A dog in Canada died of bird flu last week. In Wyoming, the State Veterinary Laboratory said in a brief statement that a barn cat tested positive for bird flu near Thermopolis, a small town in Hot Springs County, about 110 miles southeast of Casper. “This is the first report of HPAI (highly pathogenic avian influenza) in a domestic cat in Wyoming, and it likely became infected from ingesting meat from wild waterfowl,” the lab’s statement said. There was no information about the cat’s condition, but Dr. Myrna Miller, the lab’s supervisor of virology, said several semi-feral cats and skunks were recently found dead at or near the ranch. The other animals have not been tested After a previous version of this article was published on Thursday night, Dr. Miller informed BNO News about a recent case in Nebraska where two domestic cats had also tested positive for H5N1.

Dr. Sarah Sillman, from the University of Nebraska’s Veterinary Diagnostic Center, wrote in a case report that two domestic cats died in January after being infected with bird flu, presumably from predation of wild birds. The first cat in Nebraska died after experiencing a “rapid decline” in health with multiple symptoms, including weight loss, fever, seizures, tremors and loss of proprioception. “The PCR Ct value for avian influenza in the brain of this cat was remarkably low (12), indicating a very large amount of virus in the brain, as consistent with an acute infection,” Dr. Sillman wrote. Three other cats in the household were considered to be at risk of bird flu and one of them developed symptoms shortly after the first affected cat. “The cat was described as somnolent and had episodes of walking in circles,” Dr. Sillman wrote. “The cat was responsive to stimuli and seemed to eat and drink normally. It lived 10 days with neurologic impairment, when the cat suddenly became laterally recumbent with continual tremors, necessitating euthanasia.” A necropsy found major lesions only in the brain of the second cat and a test was positive for H5N1, Dr. Sillman said. The other two cats in the household did not develop symptoms and both tested negative for the virus.

“It is presumed that the two cats described here became infected from predation of wild birds infected with the virus given the circumstances of the case,” Dr. Sillman said. “Keeping cats indoors to prevent wild bird contact – particularly given the context of the current HPAI outbreak – and avoiding feeding uncooked poultry are recommendations to minimize risk of H5N1 infection.” It’s believed to be the first time that cats in the U.S. have been infected with the new strain of H5N1, which emerged in late 2021. In December, a cat living near a duck farm in southern France also tested positive for H5N1. The cat became severely ill and had to be euthanised. Earlier this week, the Canadian Public Health Agency confirmed that a dog in Ontario had died of H5N1 after chewing on a dead goose. It was the first time a dog tested positive for the new strain of the virus. In addition to the cat, Wyoming also reported that four mountain lions and a fox have recently died of bird flu. The global spread of H5N1 clade 2.3.4.4b – and the recent spread to a growing number of mammals – has raised concern about the possibility of a future variant which could lead to human-to-human transmission. So far, only a few human cases have been found after contact with infected birds. “The global H5N1 situation is worrying given the wide spread of the virus in birds around the world and the increasing reports of cases in mammals, including in humans,” Dr. Sylvie Briand, a WHO official, said on February 24. “WHO takes the risk from this virus seriously and urges heightened vigilance from all countries.”

Infected cats and dogs experience serious symptoms, but it’s unclear whether the virus is causing them.  The variants of SARS-CoV-2 that keep emerging aren’t just a human problem. Two reports released this week have found the first evidence that dogs and cats can become infected by B.1.1.7, a recent variant of the pandemic coronavirus that transmits more readily between people and also appears more lethal in them. The finds mark the first time one of the several major variants of concern has been seen outside of humans. B.1.1.7 was first identified in the United Kingdom and that’s where some of the variant-infected pets were found. The U.K. animals suffered myocarditis—an inflammation of the heart tissue that, in serious cases, can cause heart failure. But the reports offer no proof that the SARS-CoV-2 variant is responsible, nor that it’s more transmissible or dangerous in animals. “It’s an interesting hypothesis, but there’s no evidence that the virus is causing these problems,” says Scott Weese, a veterinarian at the University of Guelph’s Ontario Veterinary College who specializes in emerging infectious diseases.

Since December 2020, scientists have identified multiple variants of concern that appear more transmissible or are able to evade some 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 drew early attention because of its rapid rise in the United Kingdom; it now comprises about 95% of all new infections there. So far the impact of these variants on pets has been unclear. Though there have now been more than 120 million cases of COVID-19 around the world, only a handful of pets have tested positive for the original SARS-CoV-2—probably because no one is testing them. Infected pets appear to have symptoms ranging from mild to nonexistent, and infectious disease experts say companion animals are likely playing little, if any, role in spreading the coronavirus to people. The new variants might change that 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 Centre in the outskirts of London. The hospital had noticed a sharp uptick in the number of dogs and cats presenting with myocarditis: From December 2020 to February, the incidence of the condition jumped from 1.4% to 12.8%. That coincided with a surge of 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 all had come down with symptoms ranging from lethargy and loss of appetite to rapid breathing and fainting. Lab tests revealed cardiac abnormalities, including irregular heartbeats and fluid in the lungs, all symptoms seen in human cases of COVID-19. Seven of the animals got polymerase chain reaction tests, and three came back positive for SARS-CoV-2—all with the B.1.1.7 variant, 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 had been infected with the virus.

Earlier this week, researchers at Texas A&M University detected the B.1.1.7 variant in a cat and a dog from the same home in the state’s Brazos county. The Texas owner was diagnosed with COVID-19, and owners of five of the 11 U.K. pets tested positive for SARS-CoV-2—all before their animals developed symptoms. The Texas pets showed no symptoms at the time they were tested, though they both began to sneeze several weeks later. All of the U.S. and U.K. animals have since recovered, though one of the U.K. cats relapsed and had to be euthanized. Leroy says it’s unclear whether B.1.1.7 is more transmissible than the original strain between humans and animals, or vice versa. It’s “impossible to say” that pets infected with B.1.1.7 might play a more serious role in the pandemic, he adds, but “this hypothesis has to be seriously raised.” Shelley Rankin, a microbiologist at the University of Pennsylvania School of Veterinary Medicine, points out that the researchers have shown only a correlation between B.1.1.7 infection and myocarditis, and that they didn’t rule out other causes for the condition. “There is no evidence pets were sick because of the virus,” she says. Weese agrees that neither the Texas nor U.K. findings should sound any alarms about pets endangering their owners. “The risk of them being a source of infection remains very low,” he says. “If my dog has it, he probably got it from me. And I’m much more likely to infect my family and neighbors before he does.” Still, 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 people, Weese notes, so it’s worth exploring in companion animals. “It might be real,” he says, “but there’s no reason for people to freak out right now.”

Research cites posted in bioRxiv (March 18, 2021):

https://doi.org/10.1101/2021.03.18.435945