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."
Reference
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
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