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Can other animals catch/spread bovine TB?

 Added by  Sally
 31 May 2010, 12:21 PM

There is currently little active surveillance in the UK of bovine TB in other mammals, so why has only the badger being targeted? Whilst the primary host of bovine TB is cattle, the organism has been isolated from a wide range of species, including deer, pigs, sheep, horses, dogs, cats and rats (usually referred to as ‘spillover hosts’). Cats (estimated populations of well over 1 million feral and 7.5 million domestic pets www.cats.org.uk/media/facts.asp) and around 60 million rats (http://news.bbc.co.uk/1/hi/uk/2164999.stm), in particular, are far more numerous than badgers (around 288,000 – www.binfieldbadgers.org.uk/about_badgers.htm) and likely to live in closer proximity to cattle. Cats are more likely to drink raw milk from dairy cows. Apparently (ref. 7) ‘all mammals, including cats, are susceptible to the disease to a varying degree; cats can contract the causative bacteria (M bovis) if they come into close contact with the source of infection’ (so can presumably spread it). There have been cases of other domestic animals, such as goats and alpacas that have become infected with bovine TB. Whilst such incidents are still rare the Welsh Assembly government has ploughed ahead and now has power to enter land for the purpose of testing cattle, sheep, goats, other ruminants and swine for bovine TB (http://wales.gov.uk/docs/drah/publications/090630gwladtben.pdf).
In a post on http://peterblack.blogspot.com/2010/05/badger-cull-what-is-happening-on-ground.html on the subject of what other animals carry and could pass on bTB, Dr Dan Forman CBiol.MIBiol.EurProBiol. of the Conservation Ecology Research Team, Department of Pure and Applied Ecology, Institute of Environmental Sustainability, Swansea University
responds by saying:
'These are the facts!!! Latest data on domestic and companion animals from VLA, the BIG question here is why they do not consider the species they have identified high prevalence of TB as problems? Basic summary of 2009 data thus far:
Deer = 36% positive (includes farmed, wild and park deer)
Cat = 25% positive
Dog = 27% positive
Pig = 19% positive
Alpaca = 56% positive
Llama = 0%
Sheep = 44% positive
Goat = 0
Ferret (!) = 0
Farmed wild boar = 0 (NB: two cases this year confirmed for wild boar and TB, both on TB infected farms
HUMANS have a 1% incidence of TB, skewed to farm workers."
An increasing trend is for higher occurrences (live cultural positives) of TB in cats and alpaca (these are live culture diagnostics so cannot be argued with by the vets etc). I don't want to point fingers at any animals (all are great) but we do have an enormous feral cat population and an, as yet unquantified, deer population,
food for thought anyway…."

Pig sector frustration is mounting around current bovine tuberculosis (TB) control measures which have been labelled as disproportionate and equivalent to “treating pigs like curly-tailed cows”.
National Pig Association (NPA) chief executive Zoe Davies, along with other senior pig veterinarians, are calling for a review of the current “risk averse” policy.
The NPA has questioned the practicality of the three options pig farmers currently face when under a TB lockdown.
According to the NPA, these options are:
1. Slaughter with cleansing and disinfection: Unpopular with sow herds and pedigree breeders. Potentially OK for all-in/all-out fatteners.
2. Skin testing of entire adult herd: Difficult and potentially dangerous for farm staff, vets and the pigs themselves. Possible for smaller producers. Skin test is unvalidated in pigs.
3. Abattoir surveillance and post-mortem surveillance of all adult on-farm culls/losses: Post-mortem surveillance on all culls and losses is a completely new element and presents both cost and logistical problems. It will take at least two or three years and only really works for large herds with varied results.
Dr Davies told Farmers Weekly: “Defra has decided that slaughter surveillance isn’t sensitive enough, so farms are now in a position where, unless they decide to cull out, or try the skin test route, which for a 1,000 sow herd is completely unrealistic and unsafe, they are stuck under restrictions for a minimum of two years.”
The NPA is lobbying for:
Shorter restriction periods on pigs and herds only to come under restrictions once TB is confirmed
Better test accuracy
More AFUs (approved finishing units) for finishing pigs from restricted units
Info from: https://www.fwi.co.uk/livestock/pigs/frustrated-pig-sector-calls-on-defra-to-review-tb-rules
Cases of TB have been confirmed in domestic cats but Public Health England stress that cat-to-human transmission risk to public is very low. Let's keep in in perspective - three farmers killed in the UK and Ireland since 2010 from the routine cattle skin test ...
It appears that these cases came to light early 2013 but were not disclosed publicly. They are not in the main bTB hot spot areas. Bearing in mind the millions of cats (2012 estimate was 8 million) all over the UK are we going to see cats tested for bTB too and the mass culling of this species?
Public Health England has confirmed in a recent press release that two people in England developed tuberculosis after contact with a domestic cat infected with Mycobacterium bovis (M. bovis), Public Health England (PHE) and the Animal Health and Veterinary Laboratories Agency (AHVLA) have announced. M. bovis is the bacterium that causes tuberculosis (TB) in cattle (bovine TB) and in other species.
Nine cases of M. bovis infection in domestic cats in Berkshire and Hampshire were investigated by AHVLA and PHE during 2013. PHE offered TB screening to 39 people identified as having had contact with the infected cats as a precautionary measure. 24 contacts accepted screening. Following further investigations, a total of two cases of active TB and two cases of latent TB were identified. Latent TB means they had been exposed to TB at some point but they did not have active disease. Both cases of active TB disease have confirmed infection with M. bovis and are responding to treatment.
There have been no further cases of TB in cats reported in Berkshire or Hampshire since March 2013. PHE has assessed the risk of transmission of M. bovis from cats to humans as being very low.
Dr Dilys Morgan, head of gastrointestinal, emerging and zoonotic diseases department at PHE, said: “It’s important to remember that this was a very unusual cluster of TB in domestic cats. M. bovis is still uncommon in cats - it mainly affects livestock animals. These are the first documented cases of cat-to-human transmission, and so although PHE has assessed the risk of people catching this infection from infected cats as being very low, we are recommending that household and close contacts of cats with confirmed M. bovis infection should be assessed and receive public health advice.”
The findings of the animal health aspects of this investigation have been published in The Veterinary Record.
Molecular analysis at AHVLA showed that M. bovis isolated from the infected cats and the human cases with active TB infection were indistinguishable, which indicates transmission of the bacterium from an infected cat. In the other cases of latent TB infection, it is not possible to confirm whether these were caused by M. bovis or the source of their exposure.
Transmission of M. bovis from infected animals to humans can occur by inhaling or ingesting bacteria shed by the animal or through contamination of unprotected cuts in the skin while handling infected animals or their carcasses.
Professor Noel Smith, Head of the Bovine TB Genotyping Group at AHVLA, said: “Testing of nearby herds revealed a small number of infected cattle with the same strain of M. bovis as the cats. However, direct contact of the cats with these cattle was unlikely considering their roaming ranges. The most likely source of infection is infected wildlife, but cat-to-cat transmission cannot be ruled out.”
Cattle herds with confirmed cases of bovine TB in the area have all been placed under movement restrictions to prevent the spread of disease.
Local human and animal health professionals are remaining vigilant for the occurrence of any further cases of disease caused by M. bovis in humans, cats or any other pet and livestock animal species.
A summary of the public health investigation can be found in the PHE Health Protection report: http://www.hpa.org.uk/hpr/archives/2014/hpr01214_AA_zoos.pdf. A link to the Human Animal Infections and Risk Surveillance (HAIRS) risk assessment is available here: http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1317138638591
TB caused by M. bovis is diagnosed in less than 40 people in the UK each year. The majority of cases are in people over 65 years old, most likely due to reactivation of latent infection acquired many years ago before the introduction of control measures, including the routine pasteurisation of milk.
Overall, human TB caused by M. bovis accounts for less than 1 per cent of the total TB cases diagnosed in the UK every year. Those working closely with livestock and/or regularly drinking unpasteurised (raw) milk have a greater risk of exposure.
Information about M. bovis infection in humans is available on the PHE website: http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Tuberculosis
Advice for pet owners about M. bovis infections in companion animals is available on the AHVLA website: http://www.defra.gov.uk/ahvla-en/files/AG-TBYP-01.pdf
The article ‘An unusual cluster of Mycobacterium bovis infection in cats’ will be published in The Veterinary Record today. Advice from the Chief Veterinary Officer Nigel Gibbens is being provided to vets in a letter to The Veterinary Record. This will include a recommendation that cats diagnosed with a Mycobacterium bovis infection should be euthanased. This is due to the lack of effective drugs licensed in the UK for treatment of TB in animals and to minimise the risk of infection to other animals or humans.

“We also have a huge deer population. We know there is TB in that because traces of TB have been found within the deer carcasses”, says Warwickshire farmer, Jon Parker (www.fwi.co.uk/articles/06/12/2013/142312/bovine-tb-forces-farmer-out-of-beef-production.htm)
A vet has written to raise the question of bTB in farm cats. As he says, referring to a farm cat that died of TB at the badly affected Gelli Aur college dairy farm herd in Carmarthenshire:
"This very cat quite likely has spread bTB for years. Since few farm cats are treated as pets how many infected farm cats are still running around on this farm and on all other farms within UK? And how many have been tested for bTB ( x rayed ) ever?"
Info from: http://www.warmwell.com/

TBfree New Zealand has trapped and done autopsies on more than 530 ferrets in Marlborough to check for bovine tuberculosis.
The Marlborough trapping covered about 135,000 hectares.
The scavenging habits of ferrets meant they could pick up TB from infected wild animal carcasses.
Info from: www.stuff.co.nz/business/farming/agribusiness/9067589/Ferrets-checked-for-TB
Cats pose little no risk to human health says Cats Protection - http://mrcvs.co.uk/en/news-story.php?id=10042
"Many cats which have Mycobacterial infections have spontaneously-resolving skin lesions which are not a risk to people.
"Those cats which do have tuberculous Mycobacteria lesions are most commonly infected by a type of bacteria called Mycobacteria microti, which is caught from voles and is incredibly rare in people."
Further, there have been no reported cases of humans contracting TB from a cat, although rarely, cats have become infected with TB transmitted by humans.
Cat owners have been advised to seek veterinary advice is their cat is unwell or has a lump or wound.
"In 99% of such cases, the issue will not be due to any type of Mycobacterial infection, and rarer still to be caused by a type of Mycobacteria that can infect people,"
Also from the cat group website:
'Cats being infected with TB could be risk to owners, vets warn' shouts the heading of a recent Telegraph article (www.telegraph.co.uk/health/petshealth/10150363/Cats-being-infected-with-TB-could-be-risk-to-owners-vets-warn.html). A study at University of Edinburgh found that the disease, which is caused by a bacterial infection, is more common among domestic cats than previously thought. Experts estimated that up to 100 out of every 100,000 cats could be infected with Mycobacteria. One vet said in the article that the most common cause of the disease in cats was a strain called Mycobacterium microti, which is usually found in voles.
We should perhaps note that most mammals can contract bovine TB but it is only the badger that has been subjected to detailed scrutiny. A recent report suggested the badger too may well be just a spillover host as cats and other mammals are believed to be (ie will not sustain the disease). There are several million cats in the UK compared to several thousands of badgers. Many live on farms and have just as much opportunity to mix with cattle and to drink raw milk Is this kind of scaremongering going to lead to a demand for cat culling?
In another report a seal was found to have bTB. In the same article an Yvonne Squire, from Torrington in Devon, had a kitten who caught bovine TB. She said: "He was attacked by a feral cat. I took him to the vet with a terrible bite. The kitten got worse. I took him back to the vet. They did all these tests. They phoned me up to say my little Alfie had TB and he had to be put down. He said there was a dog there who also had it."
Email from Prof PT saying he doubted it was true - if so it would be widely published in the medical journals and elsewhere...just anecdotal... Its also a notifiable disease....I really think if it is true the powers that be would be singing from the rooftops about it, as it can be used to justify killing badgers...
He sent the Defra figures for bovine TB infections in none cattle species up to 2012. You can see that there are just 9 confirmed cases in cats for 2012. Looking back over the last decade there is a clear trend upwards in cats. Following the trend upwards in cattle, probably because farmers like to give kitty a saucer of (unpasteurized) milk in the milking parlour... see http://webarchive.nationalarchives.gov.uk/20130315143000/http://www.defra.gov.uk/statistics/foodfarm/landuselivestock/cattletb/other/
Our attention was drawn to a posting at http://bovinetb.blogspot.co.uk dated Friday 07 June, 2013 and headed 'Not cattle ....' It related to a debate on bovine TB that had been held in Cheltenham. Included within the piece was the following statement:
'But in questions or points from the floor, one speaker announced that in her professional capacity and at the present time, she was treating 8 people in the county of Gloucestershire for Zoonotic tuberculosis - which they had contracted during an up close and personal relationship with the family cat'.
For some reason the author(s) of this site is determined to remain anonymous so we have been unable to make contact with them but we did contact Public Health England and were told by Louise Dirks, the Public Health Practitioner of the Glos, Avon and Wiltshire area that the above statement is, in fact, erroneous.
In view of the sensitivity of the subject, we wonder why the authors chose to publish such blatant propaganda without first checking for accuracy? It certainly makes us skeptical regarding the credibility of the rest of the information set out on their blog pages.
I am aware that many animals can catch bTB, but not very many animals can catch and transmit it. while it is useful to look at spillover hosts- many of these are also reffered to as dead end hosts- meaning they can catch it and not transmit it- the pig is one such host and therefore is not included in any eradication policy.
A week after the Michigan Department of Agriculture announced the discovery of the 55th bovine TB-positive herd in Alpaena, an MDA official explained what happens next at a public meeting and the issue of wildlife reservoirs came up with deer being implicated. However, The MDA is now looking at voles, raccoons and opossums as well, the official explained. Voles are apparently especially susceptible to the disease, and curious cows could possibly lick dead animals. Finding a single dead vole in acres of land would be nearly impossible.
Interesting comment from http://bovinetb.blogspot.co.uk website (Oct 28 2012)
... Finally I am amazed that in all the discussions about bTB, the testing of dairy and beef herds and biosecurity on farmyards the role of pet cats is never mentioned. Cats can carry bTB and being a veterinary surgeon myself I do remember very well the one single cat we had finally sorted out in my home-country some 35 years ago to have infected and reinfected 3 different dairy herds in one bigger hamlet over almost 2 years. To diagnose TB in a cat the usual intra-dermal test is not reliable. The only way to do it is by radiography or by long lasting cultures of dubious excretions.
Dr. Ueli Zellweger, MRCVS, GST, GThT
New report looking at loggers that help reveal how animals interact with each other, including trials using badgers and cattle (with several refs to bTB). Full report can be read at:
Performance of Proximity Loggers in Recording Intra- and Inter-Species Interactions: A Laboratory and Field-Based Validation Study
Knowledge of the way in which animals interact through social networks can help to address questions surrounding the ecological and evolutionary consequences of social organisation, and to understand and manage the spread of infectious diseases. Automated proximity loggers are increasingly being used to record interactions between animals, but the accuracy and reliability of the collected data remain largely un-assessed. Here we use laboratory and observational field data to assess the performance of these devices fitted to a herd of 32 beef cattle (Bos taurus) and nine groups of badgers (Meles meles, n = 77) living in the surrounding woods. The distances at which loggers detected each other were found to decrease over time, potentially related to diminishing battery power that may be a function of temperature. Loggers were highly accurate in recording the identification of contacted conspecifics, but less reliable at determining contact duration. There was a tendency for extended interactions to be recorded as a series of shorter contacts. We show how data can be manipulated to correct this discrepancy and accurately reflect observed interaction patterns by combining records between any two loggers that occur within a 1 to 2 minute amalgamation window, and then removing any remaining 1 second records. We make universally applicable recommendations for the effective use of proximity loggers, to improve the validity of data arising from future studies.
Dan Rogerson: To ask the Secretary of State for Environment, Food and Rural Affairs how many mammals other than cattle were identified with or slaughtered for bovine tuberculosis as a result of (a) microbial culture sample, (b) reports from local veterinary practitioners, (c) gross pathology examinations by veterinary investigation centres, (d) disclosing diagnostic tests including intradermal skin or blood assays and (e) reports from Meat Hygiene Service examinations at abattoirs in (i) 2006, (ii) 2007, (iii) 2008, (iv) 2009 and (v) 2010. [89799]
Mr Paice: The risk to non-bovine species from TB is assessed as generally low and the surveillance system is therefore proportionate to these risks. This means figures are not collected or broken down by the specific categories the hon. Member has requested. Moreover, these scenarios are not mutually exclusive for a particular case and it would be difficult to allocate each case to one of these scenarios. In addition, TB in non-bovine species is not considered to have been “identified” until positive culture results are confirmed.
Figures from 1997 on the annual number of total samples from non-bovine animals that are (a) processed by the AVHLA laboratories and (b) found positive for M. bovis infection, are broken down by species and are available on DEFRA's website at:
(These figures do not include the number of animals slaughtered from a herd where TB has been confirmed when M. bovis is not cultured from that animal.)
Email from BH 13/8/11.
This table is always used to show TB is on the increase in 'spill over" species. But my question is .... when did MIRU-VNTR and spoligotyping come into use as tests?
It would have been after 2003 because the papers were only written then, so they must have had an effect on the positive numbers reported?
Would that be part of the explanation?, The other being vets have been made far more aware of bTB over spill species, and better informed as to where to send infected dead animals.. that would add noise to the graph and may explain the jump in numbers for the last few years? Although for the first quarter of 2011 numbers are down significantly.
Just my theory but I think most of these animals have been carrying bTB for far more years then the vets give them credit for, it was proven in the vole population in the early 30's, cats we've known of for decades, deer in the States, they worked that out in the 50's...
It's just now we have a heighten awareness of bTB and know to look for it and can easily check for it...

Some web sites are expressing concern regarding the numbers of other mammals allegedly being diagnosed with bovine TB. They also claim that the numbers are being under reported but how this can be checked we do not know. Why would such information be withheld?
The Defra statistics certainly don't reveal there is much of a problem regarding other species.
Incidents of confirmed M. bovis infection in domestic and companion animals & wild deer in GB, since 1997 (PDF)..http://archive.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/tb/documents/tb-otherspecies.pdf)
I see the Rural Affairs Minister, Elin Jones has launched a wild deer strategy for Wales. Its aim is apparently to minimise damage to farming and forestry and provide a monitor for animal health issues, such as bovine TB.
She claims the species is 'quite numerous in several parts of Wales', then goes on to say; “They are part of our natural heritage, a valued part of our biodiversity and an asset to the Welsh landscape ─ but deer can also have a number of unwelcome impacts and it is important we have a strategy to keep the population in check.” So they are to be drastically reduced along with cattle, badgers ... what next in a country where we are seeing serious declines of many once common species?
I see my book is quoted above, so I'm not sure if this is followed here or not but I wrote a submission to Defra and currently seem to have got into a debate on the Lib-Dem forum 'The Voice' re this issue. The link is http://www.libdemvoice.org/the-independent-view-why-killing-badgers-might-not-be-the-answer-22190.html#comment-154682.
Might be of interest.
Regards Dr Richard Meyer
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871352/ Interesting paper dated June 2010 on an outbreak of bovine tuberculosis in an intensively managed conservation herd of wild bison in the Northwest Territories, Canada. An outbreak of bovine tuberculosis was detected in the Hook Lake Wood Bison Recovery Project captive-breeding herd in March 2005. The study investigates the most likely source of Mycobacterium bovis and identifies difficulties associated with salvaging tuberculosis-free animals from an endemically infected herd.
Email from Paul T dated 14/10/10
Cattle are susceptible to human TB, but in the UK this is unlikely to happen as the contact rate between human patients and cattle in the UK is low. In the UK, all cattle that are reactors are slaughtered and the lesions examined at post-mortem. If there are visible lesions, a sample is taken for bacteriology and genetic analysis. If they there was human TB in British cattle, they would have found it (and probably made a big song and dance about it!) But in rural Africa which is largely subsistence agriculture with most families having a few animals, and human TB is common (compounded by the HIV epidemic), such things are much more likely to happen.
Email from Michael dated 14/10/10
The abstract on these links seem to imply that Ethiopian cattle have been found to have human TB. Are you aware of anyone asking this question in any other country, including the UK!
“Mycobacterium bovis and M. tuberculosis were isolated from 18.2% and 11.4% (n = 44) of the milk of reactor cows, respectively.”
According to the Welsh Assembly's Gwlad newsletter Issue 99 September 2010, page 13 it states that; "In some species, the disease is usually fairly mild and the animals are considered unlikely to pose any further risk of disease spread. These are called 'dead-end hosts'". It is claimed that only the badger is a source of infection for cattle although as so little research has been done on any other species this may be not be an accurate claim.
Email from GL dated 8/8/10
This statement is from The Bern draft submission, which I wrote for the Badger Trust:
"All of the many other mammals that are known to carry TB were largely ignored. Feral cats for example out number badgers in the UK by 3.3 to 1 and have a greater biomass as a species. (Source Yalden ref. 11) They are common on or near farms and are well known to be highly susceptible to bTB as a species, while badgers (as a species) are considered resistant to bTB."7
7 Stanford and Mahmood, Middlesex Hospital’s School of Pathology. 1984. Richard Meyers, The Fate of the Badger.
In an email dated 14th June Ruth said, 'We know that M bovis is endemic in populations of badgers, in areas coincident with cattle TB. For it to be endemic in a species at least some of the infected animals of that species must infect a number or many others of its kind. I don't know to what extent that occurs in feral cats, but humans were more like badgers in the 19th century! Obviously rats are another communal living animal in burrows and could and do spread various diseases (leptospirosis for example) but I do not know how susceptible they are to M bovis. Also it may be that rats do not live long enough to develop disease, as most M bovis infections are slow at developing. I do not know to what extent infection is looked at on farms where there is clear evidence of M bovis in cattle and many cattle involved with recurrent breakdowns. Have they looked at the farm cats, rats, mice, badgers, sparrows, hedgehogs etc? It would be difficult to determine the incidence of infection, the trapping and killing of many animals to assess infection by culture and PCR etc and all isolates of M bovis would have to be fully typed. In how many animals would the infection merely be spillover rather than a sustained reservoir? It may be that only cattle, sheep, cats, dogs, badgers etc have lives long enough to develop disease and spread it'.

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