Virus World

In June 2023, a fatal disease outbreak in cats occurred in Poland. Most cases tested in Poland (29 of 47) were positive for highly pathogenic avian influenza (HPAI) A (H5N1) virus. Genetic analyses revealed clade 2.3.4.4b with point mutations indicative of initial mammalian hosts adaptations. Cat viral sequences were highly similar (n = 21), suggesting a potential common infection source. To investigate possible infection routes, our group tested food samples from affected households. HPAI H5N1 virus was detected in one poultry meat sample.

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.”

Warning issued by European Food Safety Authority after 24 cats test positive for virus in Poland. Cats should be kept indoors to avoid catching bird flu, European health officials have told pet-owners as the continent battles its worst-ever outbreak of the virus. The warning has been issued by the European Food Safety Authority (EFSA) after 24 cats tested positive for the virus in Poland, sparking fear that avian influenza could be evolving to spread among certain mammals. Since late 2021, bird flu has killed millions of birds across Europe and beyond. Last year, 67 countries in five continents reported highly pathogenic H5N1 outbreaks, with more than 131 million domestic poultry lost due to death or culling in affected areas. But the rising number of infections in mammals – outbreaks have been reported in 26 species, including farmed mink in Spain – has generated particular concern. Calling for increased surveillance of bird flu in wild and domesticated mammals, the EFSA said on Thursday that “it is recommended to avoid exposure of domestic cats and dogs, and in general carnivore pets, to dead or diseased animals”. It added: “Possible measures are keeping dogs on a leash, and confining cats indoors in areas where extensive circulation of HPAI [highly pathogenic avian influenza] viruses in wild birds has been confirmed.”

In Poland, the deaths of around 70 domestic cats since June 23 are being investigated, according to local media reports.  At least 24 tested positive for H5N1, with the source of the infections yet to be determined. Reports have linked the outbreak to raw poultry meat contaminated with the virus. Elsewhere, five dogs and a cat have been infected with bird flu in Italy. The EFSA has also called for research to investigate the role that farmed and domesticated mammals could be playing in harbouring the bird flu virus and potentially driving its ability to spread beyond avian species. “Prompt generation and timely sharing of sequence data is highly recommended to promptly identify the emergence of variants with a possible increased ... potential” to jump into humans, the agency said. Earlier this week, the World Health Organisation (WHO) said that “some mammals may act as mixing vessels for influenza viruses, leading to the emergence of new viruses that could be more harmful to animals and humans.” In a statement released on Wednesday, it said that the recent surge in bird flu outbreaks among mammals could help the virus spread in humans. “Avian influenza viruses normally spread among birds, but the increasing number of H5N1 avian influenza detections among mammals – which are biologically closer to humans than birds are – raises concern that the virus might adapt to infect humans more easily.” In April, the virus was also found to “efficiently” spread between ferrets in a laboratory, the first study confirming that the virus can spread from mammal to mammal.