Just over a week ago, in Netherlands: WBVR Diagnoses Avian H5N1 In Another Fox, we looked at the latest in a series of mammalian infections reported in Western Europe by the avian H5N1 virus, which is currently sparking a record avian epizootic across all of Europe (see DEFRA: Highly pathogenic avian influenza (HPAI) in the UK, and Europe (Update #8).
While Asian H5Nx viruses (H5N1, H5N6) have a long history of infecting terrestrial mammals (see HPAI H5: Catch As Cats Can) this appears to be a relatively new development with the Eurasian H5Nx clade 126.96.36.199b lineage.
Prior to 2020, we had only seen a few instances of this sort of species jump with the Eurasian H5Nx virus, most commonly to marine mammals (see EID Journal: Highly Pathogenic Avian Influenza A(H5N8) Virus in Gray Seals, Baltic Sea). There were, however, reports suggesting that a couple of amino acid substitutions could greatly enhance its virulence in mammals (see J. Virulence : Altered Virulence Of (HPAI) H5N8 Reassortant Viruses In Mammalian Models).
Starting about a year ago, we began seeing multiple reports of terrestrial mammals infected with the Eurasian H5Nx virus in Europe - often with neurological manifestations. A few examples include:
CDC EID Journal: Encephalitis and Death in Wild Mammals at An Animal Rehab Center From HPAI H5N8 - UK
It was also only a year ago that we learned of the first human infections with H5N8 in Russia (see Russian Media Reports 7 Human Infections With Avian H5N8) which led to the classification of the Eurasian H5N8 as having some zoonotic potential (see CDC Adds Zoonotic Avian A/H5N8 To IRAT List).
We've previously seen neurological manifestations accompanying infection with some of the more pathogenic H5 subtypes in Asia, like clade 2.3.21.c (see Highly Pathogenic Avian Influenza A(H5N1) Virus Struck Migratory Birds in China in 2015), where the authors wrote:
Subsequently, a small number of H5N1 human infections have been reported in Nigeria, and in the UK. But unlike the reports on mammalian infections above, have either been described as mild, or asymptomatic.
This suggests that the novel Sanmenxia Clade 188.8.131.52c-like H5N1 viruses possesses tropism for the nervous system in several mammal species, and could pose a significant threat to humans if these viruses develop the ability to bind human-type receptors more effectively.
But these Asian clade 184.108.40.206c-like H5N1 viruses are genetically different from the European H5Nx clade 220.127.116.11b viruses, making these recent reports of neurological presentations unexpected, and worthy of our attention.
Polecat and foxes infected with bird flu
January 20, 2022
A polecat ( Mustela putorius ) was found in South Holland with bird flu. Elsewhere in the Netherlands, foxes ( Vulpes vulpes ) also appear to be infected with the virus, according to research by DWHC , NVWA and WBVR.
On January 8, 2022, a polecat was found near Dirklandse Sas on the South Holland island of Goeree-Overflakkee that was behaving very strangely. The animal turned its head uncontrollably and was completely disoriented. Such behavior often points to a nervous system disorder. The polecat was taken by animal ambulance to Vogelklas Karel Schot in Rotterdam, a shelter for wild birds and mammals. Because the symptoms were very severe, it was decided to euthanize the animal after 24 hours and to spare her further suffering. Such neurological symptoms also occur in waterfowl that are sick with bird flu. It was therefore decided to have the dead polecat tested in the lab of Wageningen Bioveterinary Research (WBVR).
The test results showed that the polecat was indeed infected with the highly pathogenic avian flu variant H5N1. The virus was detected in the animal's brain, but samples from the throat and rectum tested negative. There is currently a bird flu epidemic going on among wild waterfowl in the Netherlands and abroad. In December large numbers of dead knotted sandpipers were found along the coast of the Wadden Sea that tested positive for H5N1, and barnacle geese and swans also suffer many victims, such as in the Oostvaardersplassen , Friesland and North and South Holland.
Aggravated Mammals and Birds
It is now clear that wild mammals can also be infected with H5N1. In May 2021, infected young foxes were found in Groningen and another sick fox was found last December, now in the south of the Netherlands . For the time being, these are predators that probably contract the virus by eating infected wild birds. This way of contamination has also been shown in raptors and scavengers, such as in 2015 in a white- tailed eagle that was found to have bird flu variant H5N8 . This avian flu variant was also detected in buzzard, kestrel and peregrine falcon in the winter of 2020/2021 .
Caution is advised
The cases of bird flu in mammals now demonstrated indicate that caution is advised during this bird flu epidemic. It is known that dogs and cats are also sensitive to bird flu. Therefore, as a precaution, keep dogs on a lead in places where dead (water) birds may lie. This prevents dogs from coming into contact with infected dead birds . For walkers, direct contact with sick and dead waterfowl should be avoided as much as possible.
Cleaning up and reporting sick animals
Animal carcasses usually remain in nature, after which scavengers clean up the carcasses. However, this is not a good idea for birds that have died from bird flu. The scavengers that eat it can also get sick themselves. For the removal of carcasses, the NVWA has therefore drawn up two hygiene protocols for site managers and animal ambulances, one for birds and one for mammals . Guidelines have been published for animal aid organizations that have to deal with sick and living animals via Stichting Dierenlot . If you spot dead animals yourself, consult the bird mortality map with a schematic overview of which birds must/can be reported where. And keep in mind that wild mammals can also have bird flu.
Text: André De Baerdemaeker, Bird class Karel Schot; Margriet Montizaan, DWHC; Nancy Beerens, WBVR; Maurice La Haye, Mammal Society.
Over the past 6 years we've seen a steady increase in H5Nx clade 18.104.22.168b's host range, and pathogenicity, following a reassortment event in either Russia or China over the summer of 2016 (see EID Journal: Multiple Reassorted Avian H5N8 Viruses In The Netherlands, 2016).
We've also seen this clade expand to include Eurasian H5N6, H5N1, H5N5 viruses as well.
While once viewed as primarily a threat to wild birds and poultry, in late December the ECDC/EFSA Raised the Zoonotic Risk Potential Of Avian H5Nx. While still not considered as big of threat to human health as the Asian H5N6/H5N1 virus, clade 22.214.171.124b H5 viruses continue to evolve, making them an HPAI lineage to take seriously.