One of your dairy farming clients has a pet cat, Suzie, which has been losing weight for some months and recently developed large firm submandibular lymph nodes and a soft cough. A lymph node biopsy revealed granulomatous inflammation and a PCR test was positive for Mycobacterium bovis. There are 14 other farm cats, which don't come into the house. The dairy farm had a number of reactors at the last tuberculosis (TB) test and is currently under movement restrictions. Suzie is the much-loved pet of the farmer's young daughter. What is the best course of action?
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Martha Cannon qualified from Cambridge in 1992. She completed a Feline Advisory Bureau (FAB) residency in feline medicine at Bristol in 2000 and is an RCVS specialist in feline medicine. She now co-owns of the Oxford Cat Clinic, a feline-only first-opinion and referral centre. She is also a regular speaker at CPD events and a trustee director of FAB.
Issues to consider
When deciding whether to treat Suzie, there are a number of items which might be placed on our utilitarian scales, such as the effect on the quality and quantity of life of Suzie and its owners, financial implications for the farm, and so on. One difficulty of using this type of consequentialist analysis is estimating the likely consequences of our actions in order to correctly weigh up the balance.
M bovis is a potentially zoo- notic infection, but the risk of spread from cats to humans appears to be small – there have been no reported cases of cats passing TB to their owners. The greatest risk to humans is from spending prolonged periods of time with infected humans or, less commonly, consuming unpasteurised milk products obtained from, or handling, infected cattle.
Nevertheless, the risk of zoo- nosis is not non-existent. Some people will be at increased risk, such as small children, the elderly and the immunosuppressed. The decision to treat a cat for M bovis is therefore always contentious and the risks to the members of the household must be considered and discussed. All family members must be aware of the risks and in favour of treatment. Treatment of M bovis is not straightforward and success is not guaranteed. The more established the infection and the more disseminated it has become, the worse the prognosis for successful treatment. Even if clinical signs resolve, eradication of the organism may not have been achieved.
Euthanasing Suzie will affect family members differently and the impact can only be assessed based on some knowledge of the individuals involved. There will be sadness, even grief. There may be some sense of relief – that the ‘problem’ has gone away, that a long course of stressful treatment is not needed, that no-one is at risk of TB from Suzie and even that one source of infection for the herd has been eliminated. The financial burden of treatment for Suzie will also have been lifted. However, along with relief may come guilt – was the cat euthanased because that was more convenient than treating it? Was she ‘sacrificed’ for the wellbeing of the cattle? The family may be left feeling that they could have done more for Suzie. But for many owners, the emotional bond to their cat is increased during a period of nursing and treatment. If that treatment is doomed to fail, we do no favours to either cat or owner by encouraging treatment.
M bovis in cats is not highly transmissible and cats are in- herently resistant to infection. Furthermore, cats are not multipliers of the organism and do not shed large quantities of the bacterium in their excretions or secretions. It is unlikely that Suzie will be a significant source of infection to the other cats or to the cattle. Similarly, should any of the farm cats come into contact with the original source of infection and subsequently become infected them- selves, they, in turn, would be unlikely to spread M bovis to the cattle.
It should also be noted that under the Tuberculosis Orders currently in force in England, Wales and Scotland, the identification of M bovis in clinical or pathological samples taken from any mammal (except humans) is notifiable to Animal Health.
Possible way forward
As well as being made aware of the small potential risk to their health from ongoing contact with an affected cat, the owners also need to consider how practical it will be to dose their cat with two or three different antibiotic drugs, twice daily, every day for six to 12 weeks. In this cat's case, the infection would appear to be both well established and widely disseminated – she has been unwell for some months and now has both lymphadenopathy and respiratory signs. This reduces the prospect for her full recovery and likely tips the balance in favour of euthanasia.
If the decision is made to opt for euthanasia, the young daughter should be involved in the discussion, and she must be made aware that this decision has been reached largely in Suzie's best interest to prevent future deterioration and distress. To avoid future resentment and ill-feeling, she must understand that it has not been reached because of any financial implications for the herd if Suzie had remained on the farm.
Readers with views to contribute on ‘Farm cat with TB’ should e-mail them toso that they can be considered for publication in the next issue, or fax comments to 020 7383 6418. The deadline for receipt of comments is Friday, January 21. Please limit contributions to 200 words.
THIS series gives readers the opportunity to consider and contribute to discussion of some of the ethical dilemmas that can arise in veterinary practice. Each month, a case scenario is presented, followed by discussion of some of the issues involved. In addition, a possible way forward is suggested; however, there is rarely a cut-and-dried answer in such cases, and readers may wish to suggest an alternative approach. This month's dilemma, ‘Farm cat with TB’, is presented and discussed by Martha Cannon. Readers with comments to contribute are invited to send them as soon as possible, so that they can be considered for publication in the next issue. Discussion of the dilemma ‘Tethered dog dies’, which was published in the November/December issue of In Practice, appears on page 47.
The series is being coordinated by Siobhan Mullan, of the University of Bristol. It is hoped it will provide a framework that will help practices find solutions when facing similar dilemmas.
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