Doubtful strangles test result

[RichardC17]

Hi looking for thoughts about a “doubtful “ elisa test of 110 for strangles which the vet has described as not a positive test result but is borderline.
It’s a pre movement test to the new yard following my proposed purchase of the horse ( ISH )
This test result may not be acceptable to the new livery yard I have arranged.
Would you still purchase the horse and arrange

 

[Caol Ila]

My friend had similar results (for a horse she’d owned for a long time; not a new purchase) when she was moving yards. As she was keen to get out of where she was ASAP, she paid a couple hundred quid for the guttural pouch flush, which provides far more definitive data as to whether or not the horse is infectious. I was told that a borderline positive blood test can mean that the horse was exposed at some point and developed antibodies, but doesn’t necessarily mean that it’s currently infectious. My friend’s horse was negative after his guttural pouch flush and he moved to his new yard as planned.

For a new purchase, it depends on how much you like it and/or whether you can wait a few weeks to move it. You can retest the blood after two weeks and those antibodies can decrease if it was a recent exposure. People who don’t want to immediately shell out for the flush try the wait and retest method.

 

[RichardC17]

Many thanks for your valuable thoughts.
I have read on the forums here that because of the likelihood of false positive tests there is little real benefit in testing a horse which has no actual symptoms

 

[Caol Ila]

After my friend's positive blood test result, I spent a while researching this stuff in the web. As I understood it, "false positive" is a bit of a misnomer. Apparently the probability of the test producing results that are flat-out wrong is pretty low. But the blood test looks for antibodies, and all that means is that the horse was exposed in the previous six months or so, but never actually got the disease. Its body fought it off without ever becoming symptomatic or infectious. A negative test means there are no antibodies, no exposure, so if it's negative, it's negative and you're good to move to your new yard.

I've also read that you can have a positive result after your gutteral pouch test on an otherwise asymptomatic horse. That horse might not be ill, but if the bacteria is in its gutteral pouches, then it could still infect other horses. It's basically horsey COVID (except it's a bacteria, not a virus). So there is benefit in testing asymptomatic horses.

 

[RichardC17]

After my friend's positive blood test result, I spent a while researching this stuff in the web. As I understood it, "false positive" is a bit of a misnomer. Apparently the probability of the test producing results that are flat-out wrong is pretty low. But the blood test looks for antibodies, and all that means is that the horse was exposed in the previous six months or so, but never actually got the disease. Its body fought it off without ever becoming symptomatic or infectious. A negative test means there are no antibodies, no exposure, so if it's negative, it's negative and you're good to move to your new yard.

I've also read that you can have a positive result after your gutteral pouch test on an otherwise asymptomatic horse. That horse might not be ill, but if the bacteria is in its gutteral pouches, then it could still infect other horses. It's basically horsey COVID (except it's a bacteria, not a virus). So there is benefit in testing asymptomatic horses.

The points you make all make sense - in my case the horse has no symptoms and has not tested positive he is right on (apparently- as I would not have known until today!) the borderline between a negative test and a positive test ??‍.
The vet suggests retest in two weeks but I am in process of buying the horse ( maybe the seller will wait maybe not).
If he was going to a private stables rather than a livery I guess many buyers would proceed.

 

[Caol Ila]

Two weeks is SOP for retesting. Also, depends on if the yard you’re moving to is willing to accept borderline results.

You could do a guttural pouch test tomorrow and have definitive results within 24-48 hours, but it will cost circa £300 and it’s an invasive procedure done under sedation. When I had my horse tested before I bought him, I was willing to sacrifice small rodents to the gods of strangles for a negative blood test, because I did not want to be making these decisions. If it’s your long term companion, you suck it up, but for a new purchase, I don’t know. Tough one.

 

[RichardC17]

Two weeks is SOP for retesting. Also, depends on if the yard you’re moving to is willing to accept borderline results.

You could do a guttural pouch test tomorrow and have definitive results within 24-48 hours, but it will cost circa £300 and it’s an invasive procedure done under sedation. When I had my horse tested before I bought him, I was willing to sacrifice small rodents to the gods of strangles for a negative blood test, because I did not want to be making these decisions. If it’s your long term companion, you suck it up, but for a new purchase, I don’t know. Tough one.

I am waiting to hear tomorrow from my prospective yard.
I would do the “guttural pouch test” ( I have more familiarity with these terms now!) but I don’t actually own the horse yet. I will see what happens tomorrow ?

 

[Apizz2019]

I've been in this exact situation.

Firstly, the test you have had is the Strep Protein M strangles test, not the Elisa. Elisa gives results of <0.1 and so on etc. The cut off for the Protein M is 110 I believe.

I spoke at length with Liphook after our new pony purchase came out at 119 and 133, two weeks apart.

The lab manager at Liphook told me the Protein M test is more sensitive and the Elisa less so, so more what we term false positives for the former and more false negatives for the latter.

Despite looking into this myself, and thinking I knew what I was talking about, there is actually no such thing as coming into contact with strangles and not catching it, nor of it being in the past 6 months. To produce antibodies, the horse must have, at some point in its life, contracted strangles. There is no such thing as coming into contact and producing antibodies - antibodies are produced after an infection. Just like us, we don't come into contact with something and produce antibodies because we've had contact. We have to have had the infection, to produce antibodies, whether we've realised it or not.

Often, despite the horror stories, horses show few, sometimes unnoticeable, symptoms which can be attributed to just a a seasonal slight cough or runny nose, when in fact they have an active strangles infection. And that's one of the reasons why it's so easily spread, because so many horses are carriers and shed sporadically for a plethora of reasons, yet to the naked eye, nobody would know. Nor are horses with active infections always noticeably poorly.

We went for the gutteral pouch wash and he was clear. But without the wash, we'd never know if there were chondroids present and even if not, if he was carrying strangles in his pouches. I can't remember the technical jargon used but there is a reason why the gutteral pouches can and sometimes do retain the strangles virus.

I now know that a gutteral pouch wash is gold standard and the only way to be 100% sure a horse or pony isn't a carrier. Both blood tests are not accurate, as told to me by the expert at Liphook, yet we opt for them because its the cheapest and least invasive way of 'checking'.

I'd strongly recommend reaching out to one of the labs as they'll tell you what you need to know and can offer solid advice.

Good luck!

 

[RichardC17]

Thanks for taking the time to share your experience. I have arranged for the guttural pouch wash and will post about the outcome next week ?stressful!!?

 

[Apizz2019]

Thanks for taking the time to share your experience. I have arranged for the guttural pouch wash and will post about the outcome next week ?stressful!!?

I remember the stress only too well! ?

Good luck!! ???

 

[RichardC17]

Hi to everyone who has helped with advice here on the forum and to anyone else who can benefit from my experience.
The scope to each gutteral pouch was clear and the test result was negative for both pouches ?
He is now going to the livery yard tomorrow afternoon ?
A final bit of information is that I moved him to the vets own stabling on Monday and it was an absolute holiday for him ?

 

[Apizz2019]

Hi to everyone who has helped with advice here on the forum and to anyone else who can benefit from my experience.
The scope to each gutteral pouch was clear and the test result was negative for both pouches ?
He is now going to the livery yard tomorrow afternoon ?
A final bit of information is that I moved him to the vets own stabling on Monday and it was an absolute holiday for him ?

Amazing, I'm so pleased for you!! ??