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Decision making
Are you positive? The fate of a shelter cat
  1. Anne Fawcett
  1. Juliana Brailey


A shelter cat with recent fight wounds tested negative for FIV on an in-house test; however, it was still suspected the cat was FIV-positive and it was held for retesting. Six weeks later it tested FIV-positive and was euthanased. Subsequently, it was determined that the cat had previously received a single FIV vaccination during its stay in the shelter. As it is impossible, on the basis of serology, to distinguish between antibodies resulting from natural infection versus those that are vaccination-associated, the result may have been a false positive. What factors should be considered in determining whether to euthanase a FIV-positive cat?

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Anne Fawcett graduated from the University of Sydney in 2000 with a Bachelor of Arts degree in philosophy. She then obtained a Bachelor of Science (Veterinary) in 2003, followed by a Bachelor of Veterinary Science in 2005. She currently teaches veterinary ethics at the University of Sydney.

Juliana Brailey is a first-year veterinary science student at the University of Sydney.

There are two key issues to consider here. The first is whether euthanasia of a FIV-positive cat is ethically justifiable. Secondly, we should ask whether making decisions about euthanasia, based on a test that may yield false positives, is ethically justifiable.

Issues to consider

With appropriate management, FIV-infected cats can live as long as uninfected cats (Hosie and others 2009). Furthermore, if kept indoors, FIV-infected cats pose minimal risks to other animals. If we employ a strict definition of euthanasia as an act of mercy for alleviating unremitting suffering, FIV-positivity alone does not justify euthanasia (Levy and others 2008).

It may be argued that shelters cannot ethically justify rehoming an animal with a health condition, even if it is asymptomatic. The trouble is that cats can suffer a myriad of asymptomatic health conditions – some of which may never manifest clinically – but it is beyond the resources of shelters to definitively rule these out.

In response to the second question, it should be remembered that no diagnostic test is perfect, including the FIV antibody test. False negative results occur before seroconversion or, in the late stages of disease, due to profound immunodepletion or sequestration of anti-FIV antibodies in immune complexes (Hosie and others 2009). False positive results may be due to maternal antibodies or previous vaccination. Therefore, it is impossible in this case to tell if the cat's positive result was due to natural infection, vaccination, or indeed both. FIV-vaccination is considered non-core by the World Small Animal Veterinary Association Vaccination Guidelines Group (Day and others 2010).

Differentiation between true FIV infection and FIV vaccine-induced antibodies requires confirmatory testing via viral culture or PCR, but such tests are costly and time consuming.

In all shelters, excluding those with a no-kill policy, a positive-FIV test often leads to euthanasia of the animal. Many shelters don't pursue confirmatory testing due to increased costs, delays and difficulty in interpreting discordant results (Levy and others 2008).

A pure utilitarian would likely agree with euthanasia on the basis of a positive antibody test in a cat with a history of fighting because, in the majority of cases, the FIV-positive status of the cat would be true. If the aim is to reduce FIV in the greater feline population and ensure the health of rehomed cats, this approach results in the greatest good for the greatest number, even if a small proportion of FIV-negative cats are euthanased because of false positive results.

Possible way forward

The principles of beneficence and non-maleficence require veterinarians to maximise benefits to patients while minimising harm. In the above case, incomplete testing, poor record keeping and perhaps poor knowledge about the impact of a disease condition have led to harm (loss of life) of the patient and an unjust or unfair outcome.

High stakes decisions about euthanasia of an asymptomatic animal with a disease that may not affect its lifespan should be based on a more solid diagnosis. At the very least, it should be based on a highly probable poor prognosis based on available evidence.

A shelter may adopt a policy whereby asymptomatic, FIV-positive cats are rehomed to owners who are fully informed about the condition and agree to keep their cats entirely indoors.

Alternatively, it may be possible for shelters to look into low-cost options for confirmatory testing. Although time-consuming, this would ensure that false positive cats are not euthanased (but may not alter the approach of euthanasing asymptomatic positive cats).

It is recommended that all cats get tested for FIV before vaccination, as the FIV vaccination may lead to a false positive result that can in turn lead to the death of an otherwise healthy animal. Veterinarians and shelter staff are morally and professionally obliged to restrict vaccination to at-risk cats; a cat housed on its own in a shelter is not at risk of acquiring FIV, which is spread largely through bite wounds. Shelter staff should also keep accurate, accessible records to ensure that the vaccination statuses of cats is known before FIV testing.

Since the vaccination status of cats entering shelters is often unknown, veterinarians administering the FIV vaccination could insist that vaccinated cats are identified (eg, via a tag or a microchip number) to ensure that their vaccination status is not confused with natural infection.


THIS series gives readers the opportunity to consider and contribute to discussions 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, ‘Are you positive? The fate of a shelter cat’, is presented and discussed by Anne Fawcett and Juliana Brailey. 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 ‘Grey squirrel treatment and hand-rearing’, which was published in the October issue of In Practice, appears on page 615.

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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