I was interested to read a BBC News report today headed ‘The mysterious deaths of hares have sparked concern about the future of the species in the East of England’ (https://www.bbc.co.uk/news/uk-england-suffolk-45810869 )
Suffolk and Norfolk Wildlife Trusts are working with the University of East Anglia (UEA) to look into a recent batch of deaths. In one case 6 dead hares were found in the same field. Suspicion is falling on either myxomatosis or hemorrhagic disease, which I presume is viral haemorrhagic disease (VHD).
In the past I have found hares dead without an obvious cause of death. I assumed at the time that it may have been braxy, which is a disease which causes sudden death in sheep. It is caused by the bacterium Clostridium septicum and generally occurs in winter, when sheep eat frosted foodstuffs. I’ve no justification for this apart from sheep having died suddenly in the area. It may even be that braxy doesn’t affect brown hares.
It appears from Dr Bell that, “Myxomatosis in hares is rare but earlier this year there was a huge die-off in Spain. That was the first time it had happened”. So it seems that myxy can indeed affect hares. If it spread through hares like it did through rabbits in the mid-1950s that would be a disaster. They would have no immunity and possibly, as in rabbits, it could kill about 95%.
I have to disagree with Dr Bell’s statement, ‘For rabbits, myxomatosis is almost always fatal”. Many rabbits have now built up an immunity and are unaffected during an outbreak. They may also have a much milder infection with many surviving. It is common to find rabbits that have eyes that have healed even though one or both may still be partially closed. Some also have slight but repairing swellings around the base of the ears and/or the vent. In the earlier stages of the recovery they will be underweight but as they recover further they gain weight rapidly.
I have found that VHD kills rabbits much more quickly than myxy. It seems as if they are there in their original numbers one day and completely gone the next. They mostly die in their burrows, with VHD – at least in my experience – wiping them out completely apart from very odd small pockets. I am currently carrying out a year-long wildlife survey on a lowland Perthshire estate (which I hope will culminate in a book to complement my book on a wildlife survey of a Highland Perthshire estate). Until relatively recently this estate had hundreds of thousands of rabbits, despite an outbreak of myxy every autumn. I have now spent two months walking over more than half of the estate and have seen only one rabbit. VHD is undoubtedly the culprit.
Both myxy and VHD are vile diseases. Let’s hope that the hares dying in Norfolk and Suffolk are found to be succumbing to something less dreadful and much less virulent.