This page: There are problems with scientific studies about FIV that lead to poor policy judgements at the very least - we look ate these issues

What we are up against

Potentially fatal problems arising from scientific studies

Much of what one reads about FIV comes from two main groups of sources: professional organisation publications, and scientific studies and papers.

Most of the professional organisation documents take their information from a combination of other organisations and scientific papers - more a research of other documentation than anything original - and they list the reference material they have used.

The scientific studies and papers focus on specific areas of study, and also use references from other scientific papers to support their own studies or conclusions.

So these scientific studies and papers, and their interpretation, are the prime source for nearly all that one reads of an authoritative nature about FIV.

Although this would seem a sound footing for the information produced, there are inherent problems which can spread through much of the published information.

Problems with some scientific papers:

There are two main problem that arise -

Firstly, there is usually a limited time scale within which a scientific study needs to be completed. This has the inherent problem when FIV is the subject, in that FIV is a very slow developing virus, and real observations would need many years of study, which are not usually available.

Their solution tends to be by artificially infecting cats with the virus in the laboratory, and in order to get results within their time frame, they would need to use a highly virulent strain of the virus, and also to inject a large volume of virus in order for the reactions to take place quickly by flooding the system with strong virus.

The problem with this is that it is not representative of natural real-world infection with the virus, which starts with a minute amount of normal field virus, and would then take many years to develop whilst the immune system works to hold the virus at bay - it can't eliminate it, but it can hold it back. So, any results from the artificially-infected cats would not be representative of naturally infected cats living normal lives.

By way of an example, say one was studying the effects of rainfall on an area; the ground could cope well with the average level of rainfall and no problems would arise. But, say a full month's worth of rain were to fall in one day (as has happened more regularly lately) what then? The area would be overwhelmed, there would be flood and devastation - a totally different effect and completely unrelated to how average rainfall affects the area.

The same could well be true of artificially infected cats.

This very problem was highlighted many years ago in FIP research.
In an interview with Dr Diane Addie, who is a scientist and world expert on FIP, Dr Addie describes how her studies, which only used naturally infected cats, had overturned many of the results from earlier studies from lab-infected cats :
interview extract:
"It would seem that you're saying that using purposely infected laboratory cats to study the disease was actually counter productive and led scientists down the wrong path entirely?"
DR ADDIE: "Absolutely!"
This (new) research has overturned 40 years of research based on laboratory strains."
(see interview details at end of this page)

The second main problem is when the actual results of a study are analysed; the interpretation of the results are just that, interpretation, not usually anything finite.

Even after the paper is published, the way it is read, and the understanding of the results and conclusions may not be truly representative.

There is one prime example of this with regard to the FIV research, the results of which have been misrepresented over and over again.

The example relates to a  long term study (1988-1998 - published in 2000 - also by Dr Addie) of a household of cats with a combination of viruses, (FIV, FeLV and FCoV). This study was essentially good, in that it involved naturally-infected cats, and was undertaken over a period of ten years, many times longer than the majority of studies. So essentially this study avoided the main problems described above. Even the conclusions of the study were straight reporting of the observations, without much interpretation, so, all in all, seemingly a good study and paper.

However, after its publication, the problems began.

The main element of the study which is relevant to the FIV story, is that, within the enclosed household of, initially, 26 cats with a combination of the viruses mentioned, there were, over a period of six years within the study (1989-1994 incl) six cats, who were initially FIV negative, who became FIV positive.

The study did not state how transmission took place, just that it did.
The study stated that 'no fighting was observed', but it did not state that there was no fighting. This may sound pedantic, but is of huge significance, as will become evident.

The problem arises when this study is used as a reference, claiming it supports the non-fighting transmission of the FIV - which the study did not actually show - it did not determine how transmission took place.

The interpretation that this study gives evidence that the transmissions took place without fighting is flawed. But that is just the start of the problem.

If any of those who subsequently used this study as reference for their own papers, actually studied the original paper, they would know that it did not prove transmission without fighting, yet this paper has been used time and time again as the prime reference to show the risks of so-called 'casual' or 'social' transmission of FIV.

The problem is exacerbated by the fact that some papers which use that paper as reference, are themselves then used as reference in other papers, so the initial flawed interpretation is then replicated in the next level of papers - and so on - effectively spreading the false information in the way a virus would spread!

That one study paper is used as reference in almost every subsequent paper relating to transmission of FIV - in all cases as reference to (falsely) support the evidence of casual transmission.

If we go back and take a closer look at the original study and paper, it shows a high density cat population (26 cats initially) within a closed household, with free mixing of all cats with each other.

The later interpretation by others that the transmission of FIV that took place was without fighting, does not take into account that it would be obvious that observation of all the cats, 24 hours a day, 7 days a week, for ten years would clearly be impossible.

Also the fact of a high number of cats in a close, closed environment, would be very likely to cause some individuals to be stressed - the mixture of personalities etc exacerbating this further.

The study reported that there was some 'paw flailing', and it would be very unwise to ignore the possibility that in a very few isolated instances (on average, once a year for six years) this might have gone beyond paw flailing into a short spat in which a bite could have taken place. The fact that cat fur is very good at concealing a single bite, adds to the possibilities that these events could have gone unobserved.

Add to this, the fact that, in the 20 years since the last transmission in the study, there have been increasing numbers of households with FIV positives living alongside FIV negative cats. One would have expected a growing number of reports of this 'casual' transmission - yet there are none reported in normal domestic households in all that time, which would emphasise the improbability that there would have been these six in one household.

In the study, there was no actual evidence either way, but the balance of probabilities would suggest that the occasional unobserved bite was the most likely cause.

The difference in probabilities between unobserved bites, and non-fighting transmission (not experienced since), suggests that the likelihood of actual 'casual' transmission diminishes with every year that passes without any other reports of casual transmission - 20 years so far with an ever increasing number of mixed positive and negative households.

Incidentally, of the first 623 FIV cats listed on the '1000 FIV cats' project, 408 individual cats (65.5%) have lived in households together with negative cats, and as yet there has not been a single report of transmission within the household.

However, of all the 'authoritative' papers in circulation, all suggest that the paper in question supports the risk, albeit low, of casual transmission.
This, in turn, is used by the majority of organisations as the reason to insist that FIV cats be homed as single cats, or only with other FIV cats.

This policy effectively makes the homing potential of FIV cats extremely restricted - for no good reason.

So the misrepresentation of this study has led to a large number of FIV cats being put down if not able to be homed as single cats - which is the policy of most large rescue organisations in the UK - all without any real evidence that casual transmission ever takes place.

It is interesting to note that, in the '1000 FIV cats' project ( there is a marked difference between attitudes in the UK and in the USA :

In the UK, only 25% of FIV cats listed are housed in indoor-only, multicat households.

Whereas in the USA, over 78% are housed in indoor-only multicat households.

This marked difference shows the restricted chances FIV cats have if they happen to be in the UK.

This would seem to be primarily due to the stated policies of the major national homing organisations, most of whom take their policy information regarding FIV cats from the Cat Group, which is led by ICC (International Cat Care - originally FAB).

The current Cat Group policy on homing FIV cats states: "this must be to a home where there are no other cats... It may be that such requirements cannot be fulfilled. In these circumstances the cat should be euthanased."

If you look at the Cat Group policy document, you will see that this same study paper mentioned above, is listed as the sole reference for this section of policy.
So they recommend the death of an FIV cat
rather than it be allowed to live with other cats,
with no real evidence of any risk!

We also note that the Cat Group document is dated 2006 - perhaps it is time they revisited it?

One wonders whether those who compiled the policy, and also those who slavishly follow it, have actually looked any further, or even studied the paper they use to condemn so many FIV cats to an unnecessary death.

It is about time that all those who are responsible for decisions about FIV cats, took their responsibility seriously, and actually looked at the evidence and thought for themselves rather than slavishly following and hiding behind false information.


'1000 FIV cats' project -

Paper referred to above:
Veterinary Record 2000;146:419-424 doi:10.1136/vr.146.15.419
Papers & Articles
Long-term impact on a closed household of pet cats of natural infection with feline coronavirus, feline leukaemia virus and feline immunodeficiency virus

D. D. Addie, PhD, BVMS, MRCVS1, S. Toth, PhD, DVM1, S. Reid, PhD, BVMS, MRCVS1, O. Jarrett, PhD, BVMS, MRCVS, FRSE1, J. M. Dennis, BVMS, MRCVS2 and J. J. Callanan, PhD, MVB, MRCVS, MRCPath3

Extract from interview with Diane Addie:
By: Val MacQueen & Dr Diane Addie

VMQ: Dr Addie, I know that for your research, you refuse to use laboratory cats (meaning, I think, that you do not infect healthy cats in order to study the progress of the disease). Most cat owners would heartily approve and be most grateful to you, but can you tell us how you study the disease without subjecting laboratory cats to it?

DR ADDIE: My research relies entirely on samples I receive from naturally infected cats. Their humans and vets send me their faeces and from time to time their blood samples. When, in the course of time, they die, they also kindly send me their bodies for post mortem.

This research has overturned 40 years of research based on laboratory strains of feline coronavirus being injected into laboratory cats.

VMQ: It would seem that you're saying that using purposely infected laboratory cats to study the disease was actually counter productive and led scientists down the wrong path entirely?

DR ADDIE: Absolutely!

Full interview can be seen [here] (opens in new tab/window)

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