OK, when I was doing my first live continuing professional development, I, I showed this photo and I asked the delegates there what would they expect this cat to have, and a wit in the front row said two eyes, and of course I meant which virus, and you can see that this is a battered old cat that's got chops. He's a Tom that's recently been neutered. He's been in lots of fights.

And in fact, he was a stray cat in Glasgow who then got adopted by my late friend Carol McCay who of course named him Nelson after he lost his eye. When I was doing my PhD, I was working with a group who were FIV workers. In fact, I was the only coronavirologist and among them, the only person researching FIP, and at that stage, young scientists had to give.

seminars to the to each other every few weeks to let people know what you're up to. And when we returned to the office, the shared office with the other. In Well To me, oh.

FIP really doesn't exist. I thought it was so I I was the expert anyway, . As if you attended my FIP lectures, I made the point very heavily that FIP tests have resulted in more deaths than the disease itself, that an incomplete understanding of FIP tests tended to be lethal for our patients, and I make the same point here for FAOV and FIV tests, and that was why when webinar vet asked me to.

To cover FOV and FIV, I wanted to hone in on this because there have been a number of recent developments in the field that can definitely result in the euthanasia of perfectly healthy cats, and I thought that we could save more lives by concentrating on that. So I'm not going to cover clinical signs, vaccination, and prevention, anything like that. Just look at the at the diagnostic test.

And Gold Capetal in 2008 wrote that the results of our study suggest that cats such as serro positive for FLV antigen or FIV antibody are more likely to be euhanotized than ser negative cats, and that is a real tragedy. And so I hope that by the end of this seminar, this webinar that you will all understand . Better how to use these tests.

Can I ask the audience, I sound like who wants to be a Millionaire again. Can I ask the audience, are your tests predominantly in your surgery in-house tests only or in-house tests with confirmation by an external laboratory, or you send to an external laboratory only? Everyone's getting the hang of this now, Diane, I think the voting's happening much faster.

This is excellent. It's marvellous being able to do this. OK, I think most people have voted at this point, so I'm gonna stop it there, .

OK, so I'll share the results with everyone. And we've got about 50%, just over 50%, say they do in-house tests and confirm it in an external laboratory. So that's, that's the largest answer and then 32% just do in-house tests and about 17% only send them to external laboratories.

Oh, that's interesting. Thank you, James. And the next question is which of the external laboratories do they use?

So. 32% not to answer this. Is it IEX, Glasgow Vet School, Veterinary diagnostic Services, Langford at Bristol Vet School, those are both in the UK, Scannellis in France, and in the in the US or other.

Looks like you might have to add some more options for next time though, because we've got about a third of people say they use other labs. But the other options, IDEX is the most popular, just under 46% say they use IDEX, 17% use Glasgow, and then 32% other. A few use Langford and no one's using Scinnellis or Antech.

Oh. That's interesting. Thank you very much, James.

Well, I'm glad they're not using Antech and it will be clear why in a, in a YouTube video that I will be launching later this year. I'm going to go right back to basics to sort of pre-graduate level, and then go right into some really advanced stuff. So I did a a conference back in In October last year in Portugal, and it became clear from some of the questions that I got that that going right back to these sort of basics is helpful for some people.

So please, I'm sorry if, I'm sorry, most of you will know this, but please just bear with it for a little while. We'll get to the complicated stuff shortly. An antigen is a substance which can elicit an immune response, usually a protein that can elicit an immune response.

And an antibody. Is a protein that's produced by plasma cells as part of the acquired immune acquired immune response to an antigen. So the antigen in this case will usually be the virus, FELV.

Well, it will be the virus, FELV or FIV and what we're talking about just now. Feline leukaemia virus tests detect the antigen P27. Feline immunodeficiency virus tests detect antibodies.

And PCR tests detect DNA or RNA and when it's RNA we call it reverse transcriptase, PCR because we use the enzyme reverse transcriptase to make a DNA copy of the RNA. FIV and FEOV are both RNA viruses. Both viruses carry the enzyme reverse transcriptase, which makes a DNA copy of the viral RNA in the host cell.

And here you can see at top left the virus attaching to the receptor on the cell surface. It enters into the cell. And with the enzyme reverse transcriptase, it makes a DNA copy of the viral RNA of the FIV or the FELV, and that DNA copy is inserted into the host DNA, and we call that inserted piece of DNA a provirus, pro viral DNA, and that is what the vast majority.

Of FEOV and FIV PCRs currently available are detecting. And the, the cell then goes on to produce virus, which is assembled at the surface by budding. And released, you can see an electron micrograph of a virus actually budding from a cell surface.

So these cells are not cytolytic. They don't burst the cell the way, for example, calicivirus does. And the infected cells may remain intact and go on producing virus.

And in the case of FELV they produce, they just released the antigen P27 on its own, which is quite a peculiar thing to happen, . So, as well as releasing whole virus, it releases, the cell releases P27 antigen on its own. In FOV infection and that's handy for us as vets because then we can detect it.

Another basic definition is that the sensitivity of a test is its ability to detect small amounts of antibody or antigen, and if you think about that, it's how we use sensitivity in everyday life. If you're somebody allergic to peanuts, they are sensitive to a very small amount of peanuts. The specificity of a test is its ability to detect the antibody or antigen correctly.

Usually manufacturers have to make a balance between sensitivity and specificity. So although rarely some tests appear both sensitive and specific and 100% sensitive and specific like we saw with the immuno and coronavirus antibody in the last lecture. It is rare.

It is very rare. So what you're looking for in the in your practise is a very sensitive test so that you don't miss any infected cats, and in your reference laboratory, you're looking for a very specific test that will correctly identify the virus. And you want to always use a gold standard test to confirm dubious in-house results.

The positive and negative predictive values are influenced by the prevalence of an infection in the in the population, and they're also influenced by how good you are as a clinician. So, If you're very good at spotting say you feel a leukaemia virus and you get an an anaemic cat that comes up negative, you would want to question the sensitivity of, of your test and send that test off. I'll just, I'd just like to explain now how the positive and negative predictive values are influenced by the prevalence in the population.

Take a test which Yes excellent specificity of 99% and in a population with the prevalence of 1%, so one cat in 100, say, has FALV. Just as an example, so this is a cat that really has FALV. But the test is only 99% specific, so we're going to get one false positive.

And this is the real situation in some of the northern European countries, such as the UK, where the FAOV prevalence is actually under 1%, and Germany and the Netherlands, the prevalence is now very low. In most countries of the world, it tends to be about 5%. But you can see that the result is that half of the FEOV positive tests in Britain are going to be false positives.

And that's using a test that's that's very good. Oh, sorry, I don't know how to make this go away. There it goes.

So half of them are, are going to be a false positive. In a test with the same test used in say, Portugal with an 8% prevalence, so 8 cats truly infected and 1 false positive, it will be 1 in 9 of the positive results that is a false positive. So you can see how The the usefulness of the truth of your positive test is affected by the prevalence in the population.

I've got 2 key messages on FEOV testing. In this lecture, and one of them is that message that we've just had that up to half the in-house FEOE positive results will be false positive results. And secondly, be aware that FALV PCR positive testing does not equate with active infection.

We know that about 10% of FELV PCR positive cats are actually immune. Or at least not infectious to other cats and probably not going to die of FALV. So here we have a rapid immunoigration test with two bands, in other words, it's P27 positive.

And you're going to be hopefully, I hope that the 32% who haven't been sending off to reference laboratories can begin to do so. I'm aware that they may not be available in all countries, but at Glasgow Veterinary diagnostic Services we we receive samples from all over the world. And at Glasgow, it might be the only remaining place where you can have virus isolation done.

And in virus isolation, you actually grow the sample, you grow the virus in a cell culture, which is an indication of true infectivity. And When or if RNA RTPCR becomes available, that will detect viral RNA. In other words, it will detect that the virus is actually there, so I sort of group that in there.

But apart from Zurich in Switzerland, I don't know of any diagnostic labs that are offering RNARTPCR for feline leukaemia virus. So the majority of you will probably be sending for proviral DNA PCR. If that is negative, that is usually, well, in, in the good laboratories, and the ones listed in Appendix A, that is an exquisitive, exquisitely sensitive test, and if that test is negative, you are looking at a false positive on your in-house test.

So that's a false positive. But you might think, well, hang on, this cat might have been exposed, just recently, less than 4 weeks ago, and in that case, you would do a retest. But if the cat's been in a stable situation and you wouldn't retest, you would just say this is a false positive, also depending on prevalence in your population.

Similarly, if if there was virus isolation negative, we'd think this is probably a false positive. We call these cats discordant. And we consider retest depending on whether they're healthy or sick and what their history is, whether there's any chance of exposure in the previous 4 weeks.

The virus isolation is positive. You would then ask the question, well, is the cat healthy or sick? And if the cat is sick with something that accords with the diagnosis of FALV, for example, a lymphoma or abortion or non-regenerative anaemia, then you would believe your result that the cat is FELV positive and you go on and treat with forbogen omega or whatever it is you've decided to treat the cat with.

The cat is healthy, you would retest in 12 weeks, and that is because you may have caught very early infection in a cat that's going on to develop an immunity. Explain that further and we call cats that have conflicting results on different tests, we call them discordant cats. This is a cartoon of a feline leukaemia virus antigen rapid immunoigration test, and you're going to see the sample drop from the top with some feline leukaemia virus P27 in it.

It attaches to antibody and a marker in the sample area. And then it moves along, and what you actually see in real life is a strip, just a strip of colour. And then to prove that the sample has moved adequately along and the that the test is working, you get a second strip.

So here you can see that it's working and you've got the double strips. By contrast, the FIV test in this example didn't move far enough along and there's no control test. So you would say that test didn't work in the way it's, you couldn't really say it's a false negative because you don't know if the cat actually was positive.

So that test hasn't worked. You can see the sample was dropped in. But nothing happened.

And so that's why these control tests are there so that you don't think, well, well, that's negative. What happens in a false positive is that something that appears to the antibody like P27. Attaches to these antibodies in the test and moves along.

And of course all we see again are the two strips. You don't know whether that really was P27 or something very similar to it that the antibody happened to attach to. So positive control ensures that your test is working.

And a negative control ensures that the antibody test, sorry, the antibody isn't sticking to something that it shouldn't adhere to. As I mentioned, that's a positive control, and you can see we don't have a negative control in most of these rapid immuno migration tests. So positive control controls against false negative results, whereas the negative controls against false positive results.

And here's an example of the IDE snap test that has both positive and negative control in it. And interestingly, they, they display that with blood, whole blood. But one of the tips that I've got for you today is that if you if you use plasma or serum rather than whole blood, you will reduce the number of false positives that your in-house tests give.

And you don't even need a centrifuge for that. If you just put your sample in the fridge for 5 minutes or even on the bench, it will naturally separate out and you can gently lift off the the plasma or serum from the from the top to use your in-house tests. Here's a witness test.

Again, they're showing whole blood, and this is an advert for a witness test and they're showing whole blood. I mean, whole blood is more photogenic, so I can understand why they would do that, but I, I don't know how many of the in-house kit instructions say to use plasma or serum. OK, so, choose your in-house tests.

On the basis of their performance, not of their cost. And choose the in-house tests for good sensitivity rather than good specificity. Because you can always confirm positive tests using a gold standard, you will have a lot fewer positive tests, hopefully the negative test.

So which which tests are the best? Katherine Hartmann published a paper 10 years ago now at looking at different incinic test systems for feline immunodeficiency virus and feline leukaemia virus. Oh, I just realised that I forgot to say early on that I, I tend to put my references down at the bottom here in white, and they are all in the notes as well, but I'm sorry I should have pointed that out earlier for any of you who are wanting to follow up and read the whole paper.

So in her study looking at sensitivity, the geospeed test from Biovito in France and who this test is now sold by Verbach, it did the best of the in-house tests and the first test was equally sensitive at 94.7. And the geo speed in the fast test were also very specific with just a small difference with the geospeed slightly ahead, but it's almost negligible.

It's very, they were both very good practically a tie and better than the other tests that Professor Hartmann looked at in this study. Mm since that time, Verbach have launched a trio test, which is the same as the geo test but now has coronavirus antibodies added to it. So I'm sorry, I know this is an FELV FIV lecture, but I can't help it.

I've just got to talk about coronavirus. It's in my blood, and so I'm delighted with this because it means that people will become much more, I hope, coronavirus aware. I'm also worried about it because an uneducated vet might think, well, that means the cat has FIP, and start bumping off cats that are perfectly healthy.

So like anything in life, it's good and bad. But Dr. Hartman concluded her paper with Duospeed showed the best overall overall performance and has to be considered the best in-house test for FAOV testing.

Just call me an old cynic if you will, but I always have a look at the acknowledgement sections of these papers to see who funded it, and it was IEX who funded it. But actually in this case I didn't need to look at it because the people like Katherine Hart and Craig Greeno Jared Herman Eggbrink. I know that these are all people.

I'm sorry, I don't know the others. I'm not decrying their integrity. It's just that I don't know them, but a lot of these people are known to me and I know that.

Their opinion couldn't be bought and that they that they would just publish the truth. So, in, in other words, the, the, the speed, the speed and the mega core were good in-house tests for FAOV sensitivity. I want to give an example of something that's not a false positive.

But it's slightly confusing, and that's maternally derived antibody in feline immunodeficiency infection, feline immunodeficiency virus. Now if the mother cat is infected with FIV, she will have antibodies and the kittens will suck all those antibodies and in FIV, like in parvovirus. Or panicopenia virus, the maternally derived antibodies persist an extraordinarily long time to 4 or 5 months of age, 16 to 20 weeks of age.

That's very long and I'm not totally clear why maternally derived antibody persists to different times in different infections. For example, MDA for calicivirus and herpes is usually gone by 2 or 32 to 3 weeks of the of the kitten's age, and for coronavirus, 5 or 6 we go there I go again with my coronavirus. Sorry about that.

But in FIV. And feline panleukopenia virus, it's very long lived. It may simply be that the queens have very high ituters, and in parvovirus that can interfere with vaccination, which is why we're keen to have vaccines boosted at somewhere between 6 and 12 months for for core vaccines.

But this means that if you test the kitten, and you get the kitten FIV positive, it's very likely that that kitten is not infected. And either behave as though the kitten is negative or retest at 5 to 6 months of age. And for those of you who are shelter vets, this will be an important, an important thing because obviously hanging on to the kitten is, is not really a great thing to do in a shelter.

You want them to get out into their new homes as soon as possible. It's extremely rare for FIV to cross the placenta. Almost no kittens are ever infected from their mother, unlike in feline leukaemia virus, and indeed any cat under a year old is extremely unlikely to be infected with FIV.

And so, you know, I, I'm asking the question in this lecture, is FIV and FALV testing worth it? Well, it depends partly on where you are. If you're in a country with a high prevalence of FELV, then yes, it is worth it.

If you're in a country with a very low prevalence of FDLV, you you might want just a confined FELV testing to those cats that are suspected of FELV. But with FIV there's a number of reasons why. You might query, whether it's worth testing.

I go into that in a moment. However excellent a test is, it will always function better in the hands of a good and knowledgeable clinician and be dangerous in the hands of an idiot, just as some of our treatments can be dangerous in the hands of an idiot. As I already pointed out, these cats are likely to be euthanized for no good reason.

There's some surprising facts about FIV and probably this is fairly widely known that maternally derived antibody survives an unusually long time, persistent unusually long time. And I want to talk now about FIV infected cats having the same life expectancy as the negative cats, the uninfected cats, that's a surprise for a number of people. And I'm not going to talk about this because it's a diagnostic lecture, but who resist putting it in that cats are more susceptible to FIV infection for about 2 to 3 months after routine vaccination.

That's a very little known fact. When we give a booster. Do we say to people now.

If your cat goes outside, they're more likely to get FIV infected than they were before the booster. I don't think that would be very good for business. But it's true.

It's just something to bear in mind and as Sally mentioned earlier on in the ABCD we do advise that boosters are given not just unthinkingly every year, but every 1 to 3 years depending on the cat's environment situation. So this is a reason to bear that in mind. OK, let's look at this.

Curious finding that FIV positive cats survive. At least as long as the uninfected cats, and I started this, I'm guilty as charged in 2000 with a publication in the vet record where they I was following a household of 26. Cats that had FIV, FAIV, and coronavirus endemic in the household, and I found that the FIV positive cat survived for an average of 51 months, and the negative cat, 17.5 months.

And Professor Jarrett used to like to tease me that I was going around saying that FIV was life enhancing, and I wouldn't have gone that far. He just liked teasing me a lot, but it was very odd and unexpected and finding. Dominique Pointier, excuse me, I'm gonna have to take a drink.

Sorry about that. Dominique Pontier in France, in an unpublished study of feral cats, got exactly the same response that the positive cats were surviving at a long time. Some more cats die of the test on the infection.

And Julia's Julia Beachy's group published a similar in 2013, and they wrote a negative effect of FIV on survival was not apparent in this study. I found at least 4 studies that confirmed this effect. The outcome of FIV infection was poor in a rescue multi-cat environment and in a paper by Powell Bekowski and Margaret Hosey's group compared to cats living in single and two cat households.

So group one. There was a group of cats, 17 cats that were just an ordinary pet household, and group 2 was 27 FIV infected cats in a in a a rescue shelter. And the cats in the shelter did very much more badly than the cats in the households, and here on the right we see their weights in group one, the group one cats seem to actually gain a little weight, whereas the cats in the shelter lost weight.

And in the paper they concluded that that was possibly due to the effect of coinfections in the shelter. Unfortunately we can't see they don't have a control group of FIV negative cats in these two groups, which would have been very interesting to see if shelter cats. We're doing this anyway and you would expect.

They didn't record that they were dying of FIP but one would expect that some of them probably were. So go back to Nelson, Carol's cat Nelson, and ask yourself if you were presented with this cat. If I do an SIV test, how, how will I proceed?

Will it make any difference? For myself, when I, I've only had one FIV infected myself and my tendency was to treat anything much more promptly because I was aware that she had HIV, so it may affect what the guardian of the cat's family do with the cat. They may be much more likely to come to the vet quickly if they know the cat has FIV so it might make a difference.

FIV is an infection of, of outdoor cats, seen here trying to get some. Mycobacteria from the fresh milk. I shouldn't say that.

All the cows are mycobacteria negative these days. So it's not really a condition of indoor cats, and it's especially not a condition of pedigree cats, breeders' cats. So why are we testing every year FIV testing these cats when they're always kept indoors?

Admittedly some people have indoor or outdoor cats. And that's where again I'm very pleased to see this test because it makes a lot more sense to test breeders cats for coronavirus antibodies than FIV antibodies because the pedigree cats have quite a high chance of going on to develop FIP. Coming back to Captain Hartmann's paper, which was the best FIV in-house test?

Well, it was a snap combo. However, for those of you who are in, sorry, you'd be asking where did our, our geospeed or reospeed test come and it actually came after the fast test, . By a whisper again, they were pretty much the same and came 3rd to the combo test.

As I've already mentioned, I . Funded that and just to show you, they really did say prices not prices, but as I've already mentioned, these are, this is a group I believe. In a more recent some more recent tests, unfortunately, the geospeed wasn't included, but what was found for those of you in countries with the FIV vaccine was that the snap combo couldn't differentiate between FIV vaccinated cats and naturally infected cats.

But the antigen rapid and the witness test. And both did differentiate between vaccinated cats. So which test you would choose for FIV will depend on which country you're in.

And whether or not the FIV vaccine is available, it's not available in a lot of Europe, certainly. So is there any point in doing an FIV test? Will you do anything differently, given that the prognosis for FIV positive and negative, it was the same for, or was the same at least 4 studies?

And the prevalence of HIV is so high that euthanasia of a healthy FIV positive cat is never justified. You can't say, well, if I let this cat outdoors or if I'm doing a trap neuter return and I replace this, this will, this cat will infect other cats. I did a attract you to return in inner city Glasgow in Scotland, and I simply put the cats with FIV back because so many of them had FIV that one more or less wasn't going to make the difference.

I wasn't going to kill a healthy cat for nothing. Will you, how would you confirm these tests? At Glasgow, we have an immunofluorescent antibody test where they, where we follow up with a western blood or immunolo when necessary.

Bienzo Eal published a paper looking at PCR testing, and Laboratory X was their own research laboratory. Laboratories Y and Z were mysteriously termed commercial laboratories, but they didn't say who they were, and they sent off dog samples as a control and look at this, they got positives from their dog samples which couldn't possibly have been infected with feline immunodeficiency virus, and their conclusion was. The PCR tests currently available for FIV infection are unreliable, with highly variable sensitivity and specificity.

So no, I wouldn't be using FIV PCR tests. Antibodies to FIV appear 6 to 12 weeks post infection. This is a western blood.

These are the . The Antigens of the FIV GP glycoprotein 120, 55, 2417, you can see antibodies to P24 are appearing at 6 weeks. This is one of Margaret Rose's papers, and that really they don't have a full plan of play of antibodies until about 9 to 12 weeks.

So in practical terms. If a cat has had a fight with an FIV positive cat, and you're worried about infection of FIV, you would test that cat somewhere between 6 and 12 weeks post infection, and you know this yourself, if you stand with bare feet on a needle at the beach, you would you would wait 12 weeks to go and have an HIV test. That actually happened to a friend of mine.

And it was a horrible 12 weeks waiting for that HIV test to, to see if he had developed antibodies. Happily he hadn't, so 1212 weeks to be safe post infection for an FIV test. Going back to feline leukaemia virus.

And my second key message about PCR testing. I want to go into some detail here. And I want to say that a key message really if you, if you doze off and go to sleep is before you do take on board that you want to get your PCR results from a laboratory that gives you a measure of quantity.

A measure of quantity is very important, and at the moment, VDS in Glasgow, Langford do that, Scannellis do that in France, and I'm told that I hope to introduce it and and virus isolation will also . Give you, will also be a good confirmatory test. Remember that what most of these PCR tests are detecting is the proviral DNA.

Not infectious virus. I described to you how we get these PCR CTs. And what Pinches at all published about the Langford test.

PCR test was that below a CT of below 20, which means a high amount of virus, all the FVOV infected cats were all the cats were FEOV infected and all those who had a CT of less than 20. At over 25. Most of them aren't infected and that between 20 and 25, some of them are infected.

So, and of course cats that are negative that have have no signal after 40 or 45 are negative. And this is the table from Mark Pinches. Showing the CT down the left from the PCR.

Virus isolation, positive and negative. Elis are positive and negative, and just showing you that at below 20. These cats were virus isolation positive and P27 positive and none of them were negative.

At over 25 of a CT, we still had some cats that were infected, some cats that were discordant. And the majority of cats were negative. And in between that, there are various numbers.

I've got an update of the table in your notes using Glasgow figures. So you, you would want to find out for your own lab, what sort of levels these represent as well. And if they're not, if they don't know, if they're not doing that work, then That's not really a lab you should be using.

Mm Transmission of feline leukaemia virus is horizontal from cat to cat and saliva and is also vertical transplacently and in the milk. We have to watch out that it can be iatrogenic through blood transfusion, reusing dental instruments, operating instruments or needles, which I would absolutely hope none of you is doing. I'm sure you're not if you're here on this webinar then.

You You're obviously practising to very high standard. PCR is the test that we want to use for blood transfusion because well I'll, I'll go into that shortly. Following FAIV infection, you can get abortive infection.

In other words, the cats amounts a successful immune response, and this is what happens with the majority of cats over 6 months of age who encounter FLV. You can get persistent or progressive infection which is followed by FELV disease and a terribly poor prognosis, and over 80% of the cats die within 3 years. It's very different from FIV.

In fact, although FVLV was discovered earlier than FIV, it's actually a newer virus to cats, and it hasn't evolved enough to not kill its host. It's never a good idea to kill your host. Remember that next time you're a guest in somebody's house.

The difficulties for us are these cats that are regressively infected, the discordant cats, and these cats can become recovered and immune or can be latently infected for for quite some time and may or may not develop a persistent progressive infection. So the abortive infected cats are FALV negative, but have virus neutralising antibodies. That's how we know that they're, they've been exposed.

The persistent infected cats are P27 positive, so positive on your RIM tests and LISA tests. And have a high virus load, so a low CT. And as I said, these can go either way and they will have variable P27 results, variable PCR results.

So how do cats get over FALV infection? Sorry, I'll just start with the abortive infection. The killing of FEOV infected cells by cytotoxic T lymphocytes, and this is based on work of Norman Flynn in Oz Jarrett's group at Glasgow.

And this this diagram shows you infected cells, here's the virus here, and the infected cells will display viral antigen. On the surface and the cytotoxic T lymphocytes will recognise that and will release perforin, which just destroys the cells. This is a bit like a SWAT team who realised there's a baddie in the house.

So rather than using guns, they blow the house up. They chuck in a bomb. So this is what happens with the cytotoxic T lymphocytes.

Here, This is a slide. He's got the what we call in humans major histocompatibility complex displaying the antigen in cats is called the feline leukocyte antigen. So displaying a piece of virus which the immune cell recognises and destroys the infected cell, and the viruses can then be produced.

And Doctor Flynn found that that occurred within a week. He's measuring in this graph, these two graphs. He's measuring the CTL response in recovered cats versus viremic cats, and you can see that there's a lesser CTL response in the cats that became infected, persistently infected.

So, FVOV can be stopped by the immune system at the earliest stage of infection, as we've just shown. And just to remind you that this is a virus that's infected via the mouth. So it's ingested.

It has a replicated cycle in the oropharynx, and then it becomes a viremic, and it's heading for the bone marrow where they, it's usually in the bone marrow that the virus virus infected cells stay in the stem cells of of the . Of the white blood cells and so you're going to constantly get Peripheral blood lymphocytes, leukocytes infected with a feline leukaemia virus and it can also cause red cell aplasia. In fact, there's a subgroup of FELV that causes a severe red cell plasia, subgroup C, and these cats are acutely anaemic, .

Anyway, in the progressively infected cat, the virus is shared in the saliva, in the milk, and then the faeces and urine. And in the case that we just saw in Doctor Flynn's result, that the cats within a week have stopped, stopped it at this stage. From here to here takes 3 to 4 weeks, which is why we will be looking to test a cat somewhere between 4 and 12 weeks after infection if there's a possibility they were only recently exposed.

Doctor Flynn showed that virus neutralising antibodies arise somewhere between 3 to 9 weeks after post infection. And this is why we retest FV positive cats after 12 weeks. Mm I'm aware that we're coming to the end, but I was given permission to run a little bit overtime.

James, that's still OK? Yes, that's fine. Thank you.

This is my household of 26 cats that I told you about earlier. The coronavirus infected cats are in white, and you can see that almost all the 26 cats got coronavirus showing you how infectious that is. The FIV infected cats are in red and the FVLV infected cats in yellow.

And you can see that the FALV cats died out within 5 years of diagnosis. You can see how, how they died out and that this one infecting cat actually was co-infected with FIV Curiously. I'm not saying it's like honestly, Professor, if you're out there, I'm really not saying that, but I know he'll give me a hard time.

So what happened with these other cats? Why didn't, why didn't the number of cats with SEOV increase in this household? They were all in contact.

Well, they developed virus neutralising antibodies and for VNA 32 is considered a good tier. And I've got the dates here, April '89, 0. I can't, I can't remember it.

I think this was eight years later, October '87, and you can see that the FALV infected cats had all died within a few years. I've already said. They were acting as free booster vaccines, if you like, to all these infected cats, and after the last cat died off.

At the last FOV infected cat died off, some of the cats remained well immune. And other cats lost their immunity completely, so it's not a lifelong immunity as measured by VNA, but I'm sure that if they had been re-exposed, the cytotoxic T cells would once again have been successful unless for some reason they were immunocompromised. But if you have worries about giving an FELV booster, you can test for virus neutralising antibodies.

So it doesn't, they don't usually come up post vaccine. They're not detectable post vaccine, even an immune cap. And then in Professor Hoffman Lehman's group, we had a paper recently showing that if you take blood out from a cat that has viral Proviral DNAA.

So the cat's latently infected, but it doesn't have full virus. It's not an infectious cat, but you're taking the blood out to to do a blood transfusion. You, you're going to remove those cells from all that immune system, those antibodies and the cytotoxic T lymphocytes, and you can give the recipient cat feline leukaemia virus infection.

Therefore, a key message from this is that you should PCR test. All your blood donor cats, and that should be PCR. It shouldn't be P27 or even virus isolation.

It should be FELE PCR testing. All your blood donor cats, your in-house screen will not be sensitive enough to pick these up. So let's go back to this diagram that we had earlier of confirming our in-house positive results.

So, PCR test, with a CT, sorry, I lost my arrow. Here we are. The CT is less than 20.

We can assume that this is an FAOV positive cat and go on and treat, or you might get viral quantity and what we're talking about here is a high viral load. High viral load means the cat's positive. What about if you've got something in between, something in between maybe 20 and 40?

What are you going to do? Well, you could do virus isolation or if it were available RNA RTPCR. To see if the cat's actually infected, and then you would monitor that cat every 3 to 6 months.

To see whether the cat becomes, recovered or progressively infected, and this is a very dangerous virus, so. You do want to know whether a cat really has FVOV or not. And remember that it will kill infected cats within 3 80% of the cats will be dead within about 3 years.

We have found that some of these cats go on latently infected and with very small amounts at Glasgow we followed them, followed some individual cats for 10 years, just staying discordantly infected, . Pumping out perhaps P27 but virus isolation negative and then they can go either way, you obviously would want to avoid immunosuppressing such cats. So, confirmation, as I've already said, from a laboratory that gives you a measure of quantity and virus isolation from Glasgow or a PCR for the RNA which I know Zurich does, but I don't know of any other laboratory that offers that RTPCR and I've, I've given you the details in appendix one of the notes and addresses.

Mm So there we are, our Can you message us again? I'd really like to thank Oz Jarrett in here receiving an award for very generously sharing his slides and his knowledge with me. The best boss I ever had, best boss in the world.

Yeah, sorry, Anthony, if you're listening. You're a new boss, so I haven't assessed you yet, but, Oz is just an amazing source of knowledge, on this, on this disease and all diseases. Do we have any questions?

Thank you, Diane Addy. That was excellent, fantastic, talk once again as earlier. We do have a couple of questions that have come up.

One is from Mel. Given how much you were talking about how important the prevalence was, I think it's quite a good question. She's asked if there's a way that we can find out the prevalence of the diseases in your particular area.

This is a very old map. And I know that IDEs have a study ongoing at the moment showing prevalence. FALV is in blue and FIV in black.

But I know that I think ABCD are collaborating with IDEX and hopefully there will be a prevalence there will be updated prevalence data quite soon available in the UK. What I've found as I've been validating samples at Glasgow diagnostic lab is that we've got some pockets of infection in Wales. We've got a pockets of infection in in Northern Ireland.

And when I was in practise, I noticed a pocket of infection around red car in the north of England. Excuse me. As I said, there was a study in Lisbon in Portugal showing a prevalence of about 8%.

What you could do is go to PubMed and put in a search FALV and your country just to see what individual studies have have brought up for the prevalence. But be very much aware of things like if they're shelter cats or if they're. You know, if there's some kind of subpopulation selecting in some way, for example, If if it was a large diagnostic laboratory giving you a prevalence, they might have a preponderance of samples from sick cats.

Which would skew the prevalence upwards. Yes, no, that's really helpful. Thank you.

I think, I think it probably has. We've had, we won't go on for too much longer because we have overrun a little bit, but the one more question, I hope you don't mind, because I know your talk was really about testing, but Richard has asked about, chronic stomatitis in cats with FIV, and specifically what your view is on full mouth extractions for those cats. It's undoubtedly still the best way to treat these cats.

That's an an area that I'm very interested in. And then I would use verbogenomega. The, the question is probably aware of Pete Sain's paper, and there've been, there have been a few papers on using verbogenomeca either sub gingerly.

But I have I recovery myself. Who's who's already and my cat recovered on changing his food away from cereal-based diets to . To meat-based diet using applause and almon nature, but I have to say that my cat had already had all of his teeth out saved his canines and incisors, and he had had some interferonomeca.

So, looking at food, It is inexpensive and less traumatic. I think it's the first thing to do in these cats. Absolutely the first thing to do.

Many of these cats are calicivirus infection. And in Solange Gill's paper. I mentioned earlier on, the cows got rid of calicivirus was that 5 shots 3 times, given over after 2 weeks and 2 months at 02 weeks and 2 months.

So that would also be worth considering. That's great, thank you, Diane. That's probably a whole webinar in itself, that one, but Richard, I'm sorry, we still have no magic cure for this.

I really would like to find a magic cure for it. Such a painful, horrible condition. Absolutely.

Thank you. I think we'll probably call it a day there, but just let me say thank you once again to Diane for a fantastic couple of webinars and also thank you to Mariel for sponsoring the session today.