DAN: "When is sweet itch actually sweet itch,
and when is it actually neck threadworms?"
BOTH: Ooh.
DR LYDIA GRAY: Those are really good questions.
DAN: Good topic.
DR LYDIA GRAY: Is Lisa here?
Oh, it was two people.
OK.
Is sweet itch something that is common around here?
No?
DAN: We've got a big head nod in the back.
DR LYDIA GRAY: OK.
So there's a little bit of a breed predilection to it.
Like, some breed, some lines seem
to be more predisposed to it than others.
Like, my barn owner has a Lippizan.
And I think Lippizans are a breed that is genetically
predisposed to it.
So what it is--
sweet itch is there is a culicoides biting midge.
It's also called a no-see-um.
It's a gnat.
It's very, very tiny.
So the good news is that a strong wind can blow them away.
And a strong wind can be a fan.
So that's good.
The bad news is it's not so much the individual biting
of this midge that your horse is reacting to.
It's the saliva that gets injected into the horse.
It's sets up a body wide or systemic allergic reaction.
So the horse can get one bite and it
can be anywhere and in the traditional layout
of the clinical signs is that their mane it is so itchy--
itchy, itchy is the hallmark of this sweet itch.
But the mane becomes rubbed out.
The tail they also itch and it becomes,
they call it a rat tail.
Rat tail and buzzed mane are the way it's described.
The ventral mid-line, so the belly but exactly in the middle
gets all rubbed out and hairless.
And so you look at that, as a veterinarian,
and you think oh, sweet itch.
Except--
DAN: Always a curve ball.
DR LYDIA GRAY: --culicoides, such a nasty little midge.
We should try and do away with these.
They are the intermediate host for this neck threadworm.
And because terms like "threadworm"
can mean something else.
There's actually a threadworm in the intestinal tract, too.
Different story.
The neck threadworm, the word I would like to use
is onchocerca.
So the culicoides is the intermediate host
for this onchocerca parasite.
And so when the culicoides, stick with me here.
DAN: I'm with you.
DR LYDIA GRAY: When the culicoides bites the horse,
it injects not just its saliva that the horse is
allergic to but also this onchocerca parasite.
So now you've got a mane or a tail
or ventral mid-line that's having some reaction.
And all of a sudden, you're like, wait a minute.
Is it sweet itch or could it be this neck
threadworm, this onchocerca?
So how do you know?
DAN: That's what I was just going to ask you.
Do you start treating it like one or the other?
DR LYDIA GRAY: Well, this is one of those conditions
that you can absolutely start treating
and then see the response treatment
and make your diagnosis based on that.
And so the way you would treat and rule out the onchocerca
is to deworm.
You would give an ivermectin.
And if it suddenly becomes better,
then sweet itch wasn't the underlying culprit.
It was that the culicoides injected some onchocerca.
DAN: So you would start off assuming it's neck threadworms
by doing the deworming to see if you get a response from there?
DR LYDIA GRAY: Here's actually where you start.
You start by calling your vet because many--
DAN: You know your audience.
DR LYDIA GRAY: --I actually didn't know
he was sitting right there.
But many skin things can look like many other skin things.
And if you start going, well, I want to save some money
and just treat myself, you're going to find yourself
down the road--
you missed the whole show season.
You spent a lot of money and your horse is miserable.
So get the vet out and get a diagnosis.
And the diagnosis can be through a visual, a history.
Because sweet itch is very classic
and it's what the horse shows you.
And also when it starts--
time of the year and when it ends and then the fact
that it's very, very itchy.
You could also do a skin biopsy.
And then there's a really cool technique
where you can take the skin biopsy and just
put it on the farm in water.
And the larva of the onchocerca will come out
and you can see them.
So that's a quick stall side test.
And then there's some other skin conditions that look like that.
There's summer sores, which is another parasite, habronema.
And so you need to rule that one out, too.
And that one can also be treated by ivermectin.
So the sweet itch is a little bit more-- well,
it's a lot more challenging--
to treat because you have to stop the itching,
you have to possibly treat the secondary bacterial infection
if the horse has rubbed itself so raw,
and then the main thing is you have
to stop the midge from being able to bite the horse again.
Because every bite sets up the allergy reaction.
DAN: Yeah.
DR LYDIA GRAY: And keeping the culicoides, the no-see-um,
from biting a horse is very challenging.
I mean, I think it's more challenging than keeping ticks
off.
But I live in an area with a lot of sweet itch.
I don't live in an area with a lot of ticks.
I might change my story if I had to live with ticks.
But it's things like using fans, like I mentioned earlier,
keeping horses in at peak times that the midges are out, nets,
having mesh curtains on your stable so
that they can't come in and out, having a physical barrier
between the gnat and the horse.
And that means from head to toe covering them up.
And I get a lot of but Dr. Gray, don't they
get hot in the summer when you cover them up?
Well, maybe.
But if you use a light colored cover, not as
much as a dark color.
But trust me, they're more comfortable being hot
and not itchy then being not hot and itchy.
I think I said that right.
DAN: Yes--
DR LYDIA GRAY: OK.
DAN: --I think you're good.
Well, because you're putting a lot of fly sheets now.
There are some there are specifically designed
for horses who have sweet itch.
DR LYDIA GRAY: Because they cover--
they have area under here that covers the--
DAN: They even have ones that go all the way
up as like a hood over the ears and things like that.
DR LYDIA GRAY: I've seen it go all the way over to the nose.
DAN: Yeah.
And the material on that, I believe,
it's finer because those midges are so small.
DR LYDIA GRAY: And it's stretchy, some of them
too, yeah.
DAN: Because seeing a horse with sweet itch
is the saddest thing you can see.
DR LYDIA GRAY: Oh, it's miserable.
DAN: They just look so uncomfortable all the time.
DR LYDIA GRAY: Yeah they're miserable.
You can't do anything with them.
Your whole summer is ruined.
So you have to really work hard to prevent that.
But you have to make sure that it's sweet itch that you're
dealing with.
So for that I would use your veterinarian.
DAN: Absolutely, absolutely.
Perfect.