While many have celebrated the return of the Eurasian beaver to the UK’s woodlands, in forestry the news has received a less enthusiastic response. Here we look at the threat they pose to cricket bat willow – and the threat bird flu poses to them.
BEAVERS are well and truly back in British fresh waters after four centuries at least, but not everyone is over the ‘beaver moon’ about the born-again, native, semi-aquatic rodents felling trees and building dams. Not all trees munched by the Eurasian beaver match those gnawed centuries ago, with modern-day beavers apparently taking a liking to cricket bat willow, the development of which appears to post-date beaver extinction in the 16th century.
Batting for beavers
Cricket bat willow is a fast-growing and straight-stemmed variety of white willow, producing wood that is tough but lightweight and shock-resistant and therefore not prone to shattering with impact. And, with a profile of properties which renders this particular willow ideal for making cricket bats, cricket bat willow is widely and profitably grown in a wide range of wet, low-lying areas, with Essex and Suffolk as the centre of English production.
Extinction of beavers in England pre-dates the game of cricket and almost certainly development of the cricket bat willow (Salix alba caerulea).
Some sources suggest cricket bat willow is simply a variety of white willow (Salix alba) although most think it is a hybrid of white willow, perhaps with crack willow (Salix fragilis).
The taxon’s exact origin is listed as ‘unknown’. Except for the glaucous (blue-green) colour of the leaves and its straight stem, cricket bat willow is very close morphologically to the parent white willow tree (Salix alba). Cricket back willow trees are almost always sterile and propagated by vegetative means using sets cut from stool beds. Be that as it may, the wood was first used to make cricket bats at the beginning of the 19th century.
It is presumably not a tree that pre-extinction beaver populations would have been familiar with.
Nevertheless, 21st-century beavers have taken to cricket bat willow with relish according to the West Country landowner who reported damage to his trees in the pages of Forestry Journal back in 2021.
Willows in general appear to be the Eurasian beaver’s favourite feast in today’s UK.
Results from The Scottish Beaver trial conducted from 2009 to 2013 showed beavers’ preference to be: willow > ash > rowan > hazel > birch > alder.
H5N1 jumps from birds to mammals
However, developments may be afoot after highly pathogenic avian influenza (HPAI Subtype H5N1), which has been killing wild birds with abandon and came close to ruining the nation’s traditional turkey Christmas dinner, has reportedly jumped ship into a variety of wild mammals including foxes and otters. APHA (Animal and Plant Health Agency) says a number of otters and foxes have been found with H5N1 bird flu since December 2021, and are thought to have contracted the disease from eating the carcasses of wild birds which had succumbed to the virus.
Even more worrying are ‘mammalian mass mortality events’, the first involving the death of 2,500 seals along the coast the Caspian Sea, where south-east Europe merges with western Asia, and another in Peru, South America where some 3,500 sea lions have been confirmed to have died from H5N1. These events, along with an outbreak on a captive mink farm in Spain, are causing concern. Scientists think these could be the first instances of virus and disease transfer between mammals during this contemporary pandemic of the H5N1 avian influenza virus.
No infected beavers have been found yet, but producers of cricket bat willow trees and timber and spectators on the Compton and Edrich Stands at Lord’s Cricket Ground at St John’s Wood may live in hope.
The human connection
They shouldn’t get too excited because an avian influenza virus transferring from birds to mammals can be the first step in the disease realising its zoonotic (transfer to humans) potential. A zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans. H5N1 is currently being reported as though it is a brand-new disease phenomenon, but this is not the case.
The UK veterinary and health authorities are clearly trying to allay fears by telling the media how since October 2021, when the latest outbreak began, there have only been a handful confirmed human cases of the H5N1 virus worldwide, including one death in China. However, what they didn’t let on were details of a previous H5N1 pandemic (2004–2007). Human cases approached 300 in number with a mortality rate of over 50 per cent. Human deaths from the virus occurred in a number of countries including China, Indonesia and Turkey.
The same highly pathogenic H5N1 subtype that raged unabated from 2004 to 2007 originated in Hong Kong and mainland China before spreading throughout Asia, into the Middle East and Eastern Europe and finally ravaging much of Africa. Britain was largely spared apart from the odd outbreak in wild water fowl, and an outbreak in January 2007 at a ‘Bernard Matthews Farm in Suffolk’ with the loss of 160,000 ‘bootiful’ birds – but fortunately after Christmas 2006.
The major damage inflicted by H5N1 (2004–2007) occurred elsewhere in the world, with death and destruction of countless millions of farmed birds – chickens, turkeys, ducks, geese and the rest. I even recall an ostrich farm in Nigeria getting infected and the government dispatching a machine-gun battalion to cull the birds.
Transmission from birds to humans was relatively uncommon and human-to-human transmission was even rarer. However, human infections still happened in the multiple hundreds, mostly in Asia, with over 50 per cent of cases proving fatal. The death rate from COVID-19 is around two per cent. Human-to-human transmission of H5N1 was not completely proven but, according to the CDC (Centres for Disease Control and Infection) in the United States, is likely to have happened on a number of occasions. They list China, Indonesia, Thailand and Pakistan as countries where it is believed to have occurred.
Could wild boar bridge the gap?
A burgeoning wild boar population, increasingly at the forefront of foresters’ concerns across Europe, is both a potential link and real risk for the Influenza A virus (H5N1 HPAI) developing into a full-blown human disease. Similarities in the physiology of hogs and humans is what underlies and underpins the real threat of H5N1 HPAI transferring from wild boar and/or domestic pigs and into the human population. An outbreak of H5N1 in wild boar might well indicate the development of a mutation relatively easily transmitted to humans.
Wild boar is currently spreading a disease called African swine fever east to west across Europe, with outbreaks most recently reported in north-west Italy, Germany and Belgium. African swine fever could almost certainly decimate the European pig industry, but this is nothing compared to what H5N1 could do to humans.
All hands on deck
H5N1 has continued to scythe unabated through UK poultry flocks, with more than 170 cases confirmed since October 2022, but attitudes of the UK veterinary and health authorities suddenly changed in February 2023. That’s due to the death in Cambodia of an 11-year-old girl believed to have been infected by poultry kept by her family.
Scientists at Cambodia’s Pasteur Institute who genetically sequenced the girl’s virus said it differed from virus samples taken from birds and showed evidence of having ‘passed through’ a human. Back in 2004–2007 UK authorities were completely unfazed by hundreds of human cases and deaths from the virus in Asia, but I guess the COVID-19 experience has changed all that.
Professor Ian Brown, scientific services director at APHA, said they are currently reviewing the existing ban on vaccinating poultry against H5N1, the EU having already overturned its prohibition on the vaccination of poultry against this disease.
The latest reports suggest the UK government is looking into developing a lateral flow test for H5N1, with the possibility of the UK population once again being told to present their arm not completely off the cards.
Author’s note
Beavers are not the first ‘pest’ to threaten the cricket bat willow tree and by inference the game of cricket. During the 1930s cricket bat willow and cricket were perceived to be threatened by Brenneria salicis, a bacterium which causes watermark disease of the wood. This bacterial pathogen infected nearly 25,000 cricket bat willows and threatened to eradicate the existing population of trees.
Cricket bats made from infected wood would break and splinter and this caused frenzy within the cricketing fraternity, with articles such as “Willow Disease Threatens Cricket, Sport of the English!” (The Science News Letter, 1935) fanning the flames of fear.
Fortunately the cricket bat willow tree was brought back from the brink of extinction by managing the environmental conditions that were precipitating these serious outbreaks of disease.
Influenza viruses are classified according to the antigenic properties of their structural and surface proteins: the nucleoprotein (NP) [type] and hemagglutinin (HA) and neuraminidase (NA) [subtype] proteins. For instance, the so-called Spanish flu of 1918, which originated in birds but proceeded to kill 21 million people worldwide, was the H1N1 subtype, while the virus currently killing wild birds and domestic poultry is H5N1.
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