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The researchers, from the Dick Vet Equine Hospital, University of Edinburgh, Newcastle University, Istituto Zooprofilattico Sperimentale delle Venezie, and the University of Padova found that affected horses have major abnormalities in the structure of their neuromuscular junctions, microscopic sites of communication between nerves and muscles that are crucial for normal muscle function.
These abnormalities are believed to represent a toxin specific signature, effectively a ‘smoking gun’, for a neurotoxic enzyme termed a phospholipase A2.
Work is now underway to definitively identify the source of the toxin, in the hope that it will lead to novel treatments and improved diagnostics for this devastating disease.
The researchers think the toxin is likely to be produced by a microbe such as a bacterium or fungus growing on the horse’s pasture during the cold and dry weather which commonly precedes the disease.
Neurotoxic phospholipase A2 toxins are also present in the venom of many poisonous snakes, and there are many similarities between the signs of grass sickness and those of snake envenomation.
While there is no suggestion that venomous snakes cause grass sickness, it is hoped that some of the drugs that are currently being developed to treat and promote nerve regeneration in people paralysed by snake venoms can aid recovery of horses from grass sickness.
The researchers say that the neurotoxin most likely also causes the apparently identical diseases (termed animal dysautonomias) which affect cats, dogs, hares, rabbits, llamas, alpacas and sheep, and that their finding contradicts the previous leading hypothesis that grass sickness is a form of botulism.
This breakthrough is summarised in an editorial in the January 2025 issue of the Equine Veterinary Journal (EVJ).
The editorial, by Bruce McGorum and colleagues, looks at the implications of their article 'Equine grass sickness is associated with major abnormalities in the ultrastructure of skeletal neuromuscular junctions2".
Bruce said: “Identifying a probable cause of Equine Grass Sickness represents a significant breakthrough.
"We hope that this discovery will lead to novel treatments and improved diagnostics for this devastating condition.
"We are very grateful for the generous support we have received from horse owners, veterinary surgeons, scientists, charities and funding bodies.”
Bruce's editorial is currently available on Early View, free for 12 weeks, and will also be published in the January 2025 print issue of the EVJ.
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The university says that new resource, which is aimed at qualified and student nurses, will provide fresh perspectives on the interactions between nursing care, animal health and patient behaviour and how the overlap between these things can improve patient welfare and clinical outcomes.
Topics covered include clinical skills, patient handling and behaviour, wound management and bandaging, animal welfare and inpatient care. Content includes video tutorials, downloadable fact sheets and interactive quizzes.
The Royal (Dick) School’s Welfare and Anaesthesia Nurse Hayley Walters, who teaches final year vet students, said: “Knowledge and compassionate veterinary nurses improve patient welfare, so we want to share some of our educational and animal welfare expertise with a global audience.
"This new resource will help to promote the role of the veterinary nurse as a para-professional who is an essential part of the veterinary team."
For more information or to register, visit: https://www.ed.ac.uk/vet/jeanne-marchig-centre/cpd/vnos
The link emerged after six cats were taken to separate practices in England suffering with clinical signs of TB. Further tests confirmed that they were all infected with Myobacterium bovis. Seven more cats from the same household were also infected, but asymptomatic.
Researchers at the University of Edinburgh’s Royal (Dick) School of Veterinary Studies carried out an investigation to identify the source of infection.
The one common factor identified, as detailed in their paper, was that all the animals, which were kept exclusively indoors, had been fed Natural Instinct's Wild Venison cat food.
The authors concluded that whilst not conclusive (they were not able to test the food), their research provided 'compelling, if circumstantial, evidence of an association between the commercial raw diet of these cats and their M. bovis infections.
Natural Instinct withdrew the Wild Venison product last December, as some of the ingredients were not inspected in line with EU requirements.
A spokesperson from Natural Instinct said: "Everything we do at Natural Instinct is done so with the best interests of our customers and their pets in mind. We can assure our customers that Natural Instinct followed, and continues to follow, every food standard, hygiene regulation and best practice required to produce raw pet food in the commercial marketplace.
"As a responsible manufacturer, we are regularly inspected by the Animal and Plant Health Authority (APHA). We have complied with all of the necessary requirements, and consequently APHA have confirmed they are satisfied all standards have been met by us.
"Even though we no longer manufacture and sell the Venison cat product, we are continuing to work with Food Standards Agency as part of the investigation into the Venison cat food product."
The big question is what broader implications this incident has for feeding animals with raw diets.
Professor Danièlle Gunn-Moore from the Royal (Dick) School of Veterinary Studies, a co-author of the paper, said: "With this outbreak, the problem has been feeding wild venison – the law states the stalker must have their Deer stalker level 1 qualification, but this is only a 3-day course with just one day of disease recognition etc (apparently).
"Natural Instinct apparently sourced their deer from stalkers in the Edge area re TB risk. The stalker is supposed to inspect the gralloch (innards) wild ‘on the hill’ then leave it there for wildlife to eat. They only bring the carcass in skin back with them – which means significant pathology can easily be missed.
"Do we need to strength the law? Either that, or only feed raw venison from Scotland or other areas with no M. bovis (I am ignoring all the other potential infections here).
On the broader issue of feeding cats commercial raw food, Danièlle added: "In concept I think raw food can be far more environmentally stimulating – especially for housecats.
"But that is only safe if we can master 2 things: 1) be nutritionally sound – this is now possible with good companies doing this, and 2) be free of infectious agents – and this is a real problem, especially where the meat has been minced – which they need to be to get the minerals and vitamins correctly mixed in. So I don’t see how to square the circle at present."
Conor O’Halloran et al. Tuberculosis due to Mycobacterium bovis in pet cats associated with feeding a commercial raw food diet. Journal of Feline Medicine and Surgery, 2019. DOI: 10.1177/1098612X19848455
This is the second time Hayley has picked up a gong in recognition of her contribution to the veterinary profession: in 2014, she earned the RCVS Golden Jubilee Award for her teaching, clinical and international outreach work.
The RCVS has added its congratulations. Liz Cox, Chair of Veterinary Nurses Council, said: "It is wonderful to see Hayley once again so publicly honoured for her dedication to educating student veterinary surgeons and veterinary nurses at the University of Edinburgh and to helping animals in the UK and internationally both through her day job and her voluntary work.
"This honour truly highlights the importance of the work carried out by veterinary nurses in caring for animals and providing education on animal health and welfare issues and I hope it inspires other veterinary nurses to take pride in their work and their achievements."
The charity says it joins mounting evidence that brachycephalic cats, including most modern Persians or Exotic Shorthairs, are suffering from a number of health problems, including breathing problems, eye inflammation, skin infections and difficulty eating.
In the study, published open access in the journal PLOS ONE, cat owners were asked to complete a detailed health questionnaire and submit photographs of their cats so that researchers could measure the muzzle ratio and nose position ratio. 1000 valid questionnaires and 373 valid photographs were received.
The research confirmed that flatter-faced cats (of breeds such as the Persian or Exotic Shorthair), were more likely to have breathing problems and that the breathing difficulties were also associated with increased tear staining and a more sedentary lifestyle.
A previous paper, published in the Journal of Feline Medicine and Surgery (JFMS)2 showed how the skulls of brachycephalic cats are actually deformed, especially the nose and jaw.
The charity says that unfortunately, breeds of cat and dog with flat faces are becoming more and more popular, and extremes (of an already abnormal anatomy) can become instant internet celebrities. These breeds and individuals often have large or prominent eyes which are considered by some to be 'cute' because they are baby-like, and the flattened face often has an up-turned or down-turned mouth, which gives it a human or cartoon characteristic of smiling or scowling, such as Grumpy Cat.
Claire Bessant, Chief Executive of International Cat Care said: "It is very depressing to see the life which has been deliberately dealt to some breeds of cats because of a human desire to develop a certain look. I urge cat lovers to speak out and help others to understand that this is not something we should be doing to cats, and not something we should be tolerating.
"One of the best and most beautifully naturally designed animals – the cat – would not normally have any of these problems; we have created them through selective breeding.
"We should not be encouraging people to breed these cats by calling them 'cute', by being amused at their facial characteristics, or by the fact that they snore – rather we need to understand that this is human intervention that is wholly detrimental to the welfare of the cats and is simply cruel.
"International Cat Care takes an ethical view of all cat breeds and our website (http://icatcare.org/advice/cat-breeds) outlines the problems that exist for some breeds, including very flat-faced cats in the Persians and Exotic breeds. Our stance is that we should never deliberately breed cats for any feature or characteristic that impairs their welfare."
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Researchers at the University of Edinburgh's Royal () School of Veterinary Studies are to start testing whether a compound of cooling chemicals, extracted from mint, can be used to treat laminitis, a condition which affects seven per cent of the British horse population. The new project, funded by The Horse Trust and led by Professor Sue Fleetwood-Walker, builds on recent work that revealed for the first time that, there is significant nerve damage, as well as inflammation, within the hoof of laminitic horses. This explains why anti-inflammatory drugs are so ineffective in treating the pain of chronic laminitis and highlights the need for therapies to treat nerve injury-induced or ‘neuropathic' pain in horses. Prof Fleetwood-Walker's team discovered in 2006 that the ‘mint' chemicals have a pain-killing effect in laboratory studies of chronic pain. They will now investigate whether this synthetic treatment could help horses with laminitis.