Following on from an investigation into multiple cats diagnosed with tuberculosis (TB), fellow cat vet Professor Danièlle Gunn-Moore and the team from the University of Edinburgh have issued an urgent alert to people feeding Surrey-based company Natural Instinct. The company recalled the product back in December 2018 voluntarily after it was eaten by thirteen cats that went on to develop TB. Natural Instinct has advised people with the product to return them for a refund. Here is a direct link to details released on Natural Instinct's website.
Foods can become contaminated with Mycobacteria when the tissues of animals (like cows and deer) infected with TB enter the food chain. The vets involved with the outbreak have referred their findings to the Animal and Plant Health Agency (APHA) and the Food Standards Authority (FSA) to try and confirm whether the food was the source of infection but the manufacturer has admitted that some of the ingredients used in the food were not inspected in line with EU requirements. Although this does not in itself prove the food was infected with the offending bacteria, I thought I'd summarise the findings from the study published today in the Journal of Feline Medicine and Surgery and let you decide as it paints a pretty convincing picture.
A statement from the company says:
“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 market place. 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.”
So why is this newsworthy?
M. bovis is one of several species of Mycobacteria that can cause tuberculosis (TB) in mammals. We typically associate it with cows (or bovines - hence the latin name "bovis"), but many animals are susceptible including rodents, deer, cats, dogs and humans and who could forget the badger. Previously late last year, at least thirteen cats across England had been confirmed to be infected with the specific Mycobacterium bovis (M. bovis) type of TB. This number has now climbed significantly to over ninety cats and could rise further now that an official report into the first thirteen cats has been released today.
Cats have been known to contract TB infection in the past but its typically the skin meets rodent route of transmission. I have diagnosed several cats with the skin form of TB over my career both in the UK and Australia so it is not unheard of. There was a few years back a cluster of cases in Newbury, just outside The Cat Vet's own territory in Berkshire. These pet cats were believed to have caught their form of TB through hunting (usually small rodents) where infection is introduced through wounds made in the cat's skin by rodent bites and scratches. This typically presents as a wound that does not heal and is poorly responsive to routine antibiotic choices dispensed by your vet.
In recent years a lion and three lionesses were euthanased at Paignton and Whipsnade Zoos after contracting TB through eating contaminated carcasses. The main distinguishing and alarming factor about the newest cases of TB in felines is that they have affected numerous pet cats and their humans are potentially also at risk of infection. It currently looks highly likely that these cats have ingested the infectious organism in food rather than through their skin. This would explain why in this outbreak many cats have developed potentially fatal gut disease rather than the usual skin disease. Once in the body TB can spread systemically (throughout the body, a bit like cancer can) and often ends up in the lymph nodes and lungs. It can lie dormant for many years so any potential exposure should be born in mind for that cat's future health checks.
What we currently know about the recent outbreaks...
FREQUENTLY ASKED QUESTIONS
How common is TB in cats?
It is thought that about 100 in every 100,000 cats could be infected with different types of Mycobacteria with 15% of these cats having the same type of M. bovis TB found in the recent cases. Before any members of the trigger-happy badger cull brigade start putting cats in their sites, it is important to clarify that cats tend to be an end stage host so are at minimalrisk of infecting herds of cows.
How is TB diagnosed in cats?
A tissue sample can be tested for the presence of Mycobacterial DNA using a technique called PCR (polymerase chain reaction). A blood sample to check whether a cat's immune system has been exposed can also be used to help raise suspicion of infection in ill cats. This test is an IGRA test (Interferon Gamma Release Assay). Tissues can also be cultured to see whether any Mycobacteria are present. It may sound like there are lots of ways to diagnose TB infection but it can still be difficult to conclusively diagnose.
What symptoms should I be on the lookout for if my cat has potentially eaten TB infected meat?
When TB infects the gut (gastrointestinal system), symptoms usually occur within six months and can include any (and not necessarily all) of the following:
Some cats that become infected can appear healthy as the bacteria can lie dormant but they may well go on to develop the disease later in their life. If your cat has been exposed to this food and becomes unwell at any stage of its life thereafter, then you should alert the vet so that tests can be run.
Can I catch TB from my cat?
The short answer is YES but before it creates panic, prejudice and cat abandonment, this statement needs to be qualified. TB is transmitted between humans and animals through coughs, sneezes and skin wounds. The risk of you catching TB from a cat is extremely low. There have to date been only six confirmed cases of humans catching the M bovis bacteria from their cats. To be at risk of becoming infected you firstly need to assume that your cat has itself contracted TB and this is still a relatively uncommon disease with around 100 cases of Mycobacterial infection in cats reported each year - the vast majority of which are the skin form of the disease.
Let's say for instance that your cat is an indoor-only cat and is not on a raw diet. In this situation your chance of catching TB from your feline companion(s) is minuscule. For cats known to have been potentially exposed to the infection through an outdoor lifestyle or those fed raw diets, the risk to humans seems a bit higher than previously thought. Furthermore, cats known to be infected with TB pose the highest risk for cat-human TB infection. Humans and cats that have weaker immune systems are at an increased risk if expose to TB. This would include pregnant ladies, people on chemotherapy or organ transplant medications, the very young and elderly, or those with FIV, HIV or other significant illness. To put it all into perspective, current evidence suggests that around 1% of all TB cases in people in England are caused by the M. bovis type of bacteria and most of these are contracted from drinking unpasteurised cows milk rather than close contact with cats.
I fed this food to my cat – what should I do?
If your cat is currently well then do arrange a checkup and discuss a way forwards with your local vet. If your cat is off colour or showing any other signs of being unwell (see above symptoms), you should take contact your local vet immediately.
If my cat is infected can it be treated successfully and recover?
Importantly, treatment for TB in cats is tricky as it depends on on how severe the infection is and how soon it is detected. Treatment involves a lengthy courses of antibiotics and these are not always successful. This needs to be considered when choosing to treat cats diagnosed with TB for the cat's own welfare and also since prolonged close contact with infected cats will increase the chances of humans becoming infected.
Is feeding cats a raw meat based diet (RMBD) food safe?
The outbreak of this previously rare form of TB in cats highlights the potential hazards involved with the increasingly popular trend for marketing and feeding "natural" raw diets. Choosing to feed your cat a food that many feel better reflects the food of a wild carnivore (also known as BARF "Biologically Appropriate Raw Food" or "Bones and Raw Food") is certainly not without its risks. One advantage to feeding a dry/pouch/canned food is that the cooking process used for these diets kills infectious agents like TB. Unlike some bacteria that can be killed by freezing meat, this does not eliminate the risk of infecting your cat with potentially fatal Mycobacteria.
As with any diet or medication change, there are other a lot of factors that need to be considered when contemplating feeding raw food to your cat. What may sound like a simple, wholesome choice brings different risks versus feeding the more popular commercial wet or dry food diet. It's important to understand that this diet choice could not only affect your cat, but your family too. I am not anti-raw food feeding per se, but good intentions and hope are not good enough reasons to ignore the risks involved. Batch contamination and accidental nutrient toxicity and deficiency are happen across the spectrum of raw home prepared foods through to dried kibble so risk will be present no matter what diet you choose to feed your cat. I always suggest that you look at the evidence for and against choices involving your cat's health and well-being. Choose a reliable source (not self-professed "cat people", family, friends, neighbours, pet shop owners or Dr Google!) and do so under the guidance of a veterinary surgeon who knows your cats' full medical history.
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