They warn that after an outbreak of bird flu in cats in Poland, the virus is highly adaptive to mammals

Unprecedented outbreaks of highly pathogenic avian influenza (HPAI) virus infections have occurred in wild and domestic birds in Europe and more recently in the Americas.In addition, the currently circulating Eurasian virus H5N1 subtype Found in a variety of wild mammals Examples include foxes, bobcats, raccoons, bears, otters, polecats, badgers, ferrets, cougars, panthers, opossums, seals, porpoises, sea lions, and dolphins. Mammals, including marine mammals such as seals and dolphins, are carnivorous predators in the vast majority of cases.

During the 2022/23 epidemic season in Poland (21 September 2022 to 10 July 2023), HPAI H5N1 virus was detected in 93 outbreaks in poultry and 147 outbreaks in wild birds. The first outbreak in Poland occurred on September 21, 2022.. Infections continue until 2023, with a total of 39 outbreaks in January, 17 in February, only two in March, one in May, and the most recent on July 1.

Presence of different genotypes

The vast majority of outbreaks are caused by the CH genotype of the virus. The CH genotype in Poland was first identified in mid-December 2022. Since then, it has been responsible for 58% of poultry cases and 30% of wild bird (mainly waterfowl) cases. The genotype was responsible for multiple outbreaks in poultry between December 2022 and January 2023, and has only been detected sporadically in the country since February 2023, when Replaced by BB genotype. That is, a series of complex rearrangements lead to the development of multiple descendant lineages.

Although HPAI H5N1 viruses are considered to pose a zoonotic risk and are associated with severe disease, they have only been reported to the World Health Organization to date Twelve human cases attributed to clade H5N1 subtype.

As the number of cases observed in wild and farmed mammals has increased, concerns have arisen about indirect infection of mammals by wild birds. The global spread of HPAI H5N1 viruses in wild birds has created widespread exposure opportunities for mammals, which also raises the question of possible adaptation of HPAI H5N1 viruses, which May lead to its spread among mammals.

Recently, the editor collected veterinary journalThe Polish authorities have reported that H5N1 bird flu virus detected in some cat samples from different cities.

A recently published research paper describes the outbreak and starts with the following premise: Sudden number of cases reported across the country is ‘very unusual’so they explored Food sources may be at the root of outbreaks.A parallel study examined all potential risks associated with this outbreak and Mammalian adaptation in viruses.

Indoor and Outdoor Cats

On June 19, 2023, cat owners and veterinarians in Poland were the first to raise the alarm about a deadly disease of unknown origin in cats in the country. Suspecting that H5N1 virus may be the cause of the disease, veterinarians collected swabs from four symptomatic cats during the clinical operation and tested for H5N1 influenza virus. Analysis showed the virus was present in samples from all four animals..

After veterinarians notified their cats that they were infected with the H5N1 HPAI virus, on June 23, 2023, a group of cat owners created a public database to allow people with cats with severe illnesses to keep records of their cats. This database is not an official source, but explored as a citizen science-based dataset. The database shows the national distribution of cases in Poland, but there is no discernible pattern. The outbreak has also affected both indoor and outdoor cats..

this Symptoms most commonly reported by owners include difficulty breathing, cognitive impairment, seizures, stiff limbs, unresponsive pupils, anisocoria, decreased oxygen saturation, fever, loss of appetite, and hyperglycemia. The authors comment that while these records “are not validated, they do correspond very well with the symptoms and course of the disease in the cats who were diagnosed.”

In formally studied cases, the course was similar and included loss of appetite, apathy, excessive salivation, fever, dyspnea (shallow and rapid breathing), firm and painful abdomen, sometimes urinary incontinence, and redness of the mucous membranes. Nervous symptoms such as seizures, increased muscle tension, and sometimes stiffness in the extremities.

During clinical examination, Note increased vesicular murmur and pupil constriction, unresponsive to light. Attempts to treat pneumonia symptoms with various antibiotics were unsuccessful, and the animal’s condition worsened after 1-2 days.inside In most instances, animals are slaughtered.

Prominent cytopathic effects in human cell culture

Cat samples that tested positive for the virus were submitted and all virus isolates belonged to clade Clustered with avian virus strains sampled in Central Europe since late 2022.Furthermore, the genomes of the viruses analyzed were nearly identical, which Indicates monophyletic origin and possible common source of infection. “All had mammalian-adaptation-related mutations in the polymerase gene, which allow replication at lower temperatures,” they detail. It has been speculated that the virus may have acquired this mutation in an avian host.

Likewise, the author The replicative capacity of human airway epithelial cultures was assessed. Cultures were inoculated and monitored for 4 days at 37°C. 3 days after infection, Demonstrated pronounced cytopathic effect and tissue damage in virus-inoculated cultures.

Investigation of possible routes of transmission

Next, the investigation will focus on discerning possible routes of transmission of the virus from birds to cats. From an epidemiological point of view, several characteristics were considered. First, significant similarities between sequences from clinical samples may indicate a monophyletic origin.Furthermore, the distribution of the virus in Poland and Absence of similar cases in neighboring countries implies specific geographical determinants. In the end, citizen science data collection showed that both indoor and outdoor cats were infected with the virus, “reducing the range of potential transmission routes.”

Taken together, these observations “could indicate a co-exposure, possibly through cat food.” To investigate further, Food samples consumed by these animals were collected before symptoms appear.

The authors received five frozen meat samples and detected high levels of viral RNA in one of them, suggesting is chicken freshly purchased for human consumption on June 9, 2023“This suggests but does not confirm a possible route of transmission.”

“Virus found in chicken samples Originated from a cat owner’s personal refrigerator, whose origin cannot be determined. Therefore, it is necessary to consider that it may have been contaminated, for example during transport or at home”, they point out.

Inclusion of mammals in susceptible species groups

Considering the data presented, “we recommend assessing the presence of the virus in the wild, on farms, and in other places where viral adaptation may occur.” Furthermore, “additional epidemiological analyzes could reveal potential links between cases, thereby shedding further light on Source of infection.”

Furthermore, the above facts suggest a worrying change in the biology of the circulating H5N1 virus,” enabling them to infect large numbers of wild birds that are not normally susceptible toexpanding the infection pool of birds”.

They also noted that “longer and more efficient transmission of the virus in some birds may have influenced the greater viability of the virus in summer.” Finally, Increase the number and pressure of viruses in the environment, which in turn increases the risk of its introduction into poultry populations, but also of its spread to other animal species, especially mammals. “

Therefore, “surveillance should be enhanced for poultry and also for certain susceptible mammal species kept close to infected poultry farms.”

In addition, they also emphasizedEuropean needs Include mammals in species group poses a significant risk to the spread of highly pathogenic avian influenza, in order to provide health authorities with the tools and guidance to properly manage these cases. “

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