Ask the Vet – Blister beetle toxicity in horses
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Ask the Vet – Blister beetle toxicity in horses

October 26, 2019

DAN: “I’d like to add alfalfa
cubes to my horse’s diet, though I’m concerned over
a blister beetle toxicity. Are hay cubes just as likely
to carry blister beetles? And if so, how can you tell
which are the good ones to buy? Thanks.” DR LYDIA GRAY: It’s
a great question, and I feel maybe naive
because obviously, I’m aware of blister beetles–
like, oh, alfalfa hay– and just never worried about
buying cubes, or pellets, or any other version of them. I just assumed they
were quality made. DAN: I was thinking
the same thing when I read this question earlier. DR LYDIA GRAY: I’m like, oops. DAN: I was like, oopsies. DR LYDIA GRAY: So this
answer is for all of us. And so blister beetles– I’m from Illinois, and
we’re in Massachusetts now. And I don’t know what
you think about them, but I always thought they
were a Western state problem and I didn’t have
to worry about them. Turns out, blister beetles
are found throughout the US, and they’re more common
in the East and the South. DAN: Whoops. DR LYDIA GRAY: Whoops. We would have failed the course. DAN: Thank you for asking
this question, Jennifer. DR LYDIA GRAY: There’s a couple
different species of blister beetles, and the one
that is most toxic is the three-striped
blister beetle. DAN: That does sound
pretty intense. DR LYDIA GRAY: It
does, and but also easy to recognize
him, because one of the things we’ll talk about
is you should inspect your hay. Not the hay cubes and
pellets, but actual just hay. So they produce a substance
called cantharidin. That’s the toxic agent, and
it’s quite toxic to horses and other species,
but horses seem to be particularly
sensitive to it. And blister beetle–
the way it gets his name is it can blister
the tongue, the mouth. One of the first signs is
horses that don’t normally play in their water,
because you can imagine it makes her mouth feel better. If you’ve got blisters
and ulcers and things, that they dunk their
head in the water, and they aggressively
play and splash. DAN: You’re like,
something’s going on there. DR LYDIA GRAY: That’s
right, so that’s one of those reasons why you
have to know your own horse. But it really creates that same
blistering and ulcer effect throughout the GI system. So bloody diarrhea
is another sign. Colic is probably the
first sign we see. And it does this same damage to
the renal or the urinary tract to the kidneys. Yeah, so you could
see bloody urine. It can kill a horse. If you get a large amount
of blister beetles, or the cantharidin,
the toxic principle, can kill a horse in as
little as like six hours. DAN: Six hours? DR LYDIA GRAY: Yeah. Yeah, so if you’re in an area
and you’re feeding alfalfa, you have to recognize the signs
and you have to call your vet. Now, because colic is
one of the first signs, and you’re calling your
vet about colic anyway, as long as you follow that
principle, you’re probably OK. So we talked about the signs. Things an alfalfa
buyer should do is know the supplier, so don’t
just buy alfalfa from anybody because it’s got to be quality. Ask what precautions
they took to avoid the presence of blister
beetles in the forage. And for example, I learned that
if you harvest your alfalfa before it blooms, it will
be less likely to have blister beetles in them. If your first cutting–
you can get it done, weather-permitting,
before May, they tend to emerge from the ground
in June, July, and August. So if you get your hay before
June and after August– DAN: You have a
better likelihood. DR LYDIA GRAY: Exactly. Not, I mean, zero, but better. Yeah. So we talked about
this earlier– inspect the hay before
feeding, and you look at three-striped
blister beetle. That is a little
bit hard to say. And then know the signs of
blister beetle poisoning. Now, I did find one company that
produces alfalfa hay nationwide and has a pretty extensive
quality program for ensuring that their cubes
and pellets don’t have blister beetles in them. Here’s one more scary factoid. The cantharidin is not just
in the beetle themselves, but it can be
released into the hay. And so even if you inspect
and there’s no blister beetle bodies, there can still
be the cantharidin. DAN: Aye, aye, aye. DR LYDIA GRAY: I know. So anyway, this is
what the company says. DAN: I was hoping you
were going to give me good news on that one. DR LYDIA GRAY: And I’m
going to go ahead and read their name because I’m
reading this verbatim from their website,
and I think that they are doing such a good job,
they deserve the credit. DAN: Yeah, absolutely. DR LYDIA GRAY: All right. “From harvesting and
manufacturing perspectives, Standlee–” you’ve
heard of Standlee. We sell the Apple Berry Cookies. DAN: Yeah, absolutely. DR LYDIA GRAY: “Has
well-established QA processes at their farms, production
facilities, and distribution centers to detect and
eliminate insect infestations. Furthermore, Standlee’s
quality assurance personnel continue to be
diligent and regularly contact the University of
Idaho extension offices in each county near
their forward sources.” So see even they contact
their county extension office. And then they
harvest their forage “before abundant blooms exist
to provide high quality, high protein products
and cut down on pests. Also–” and I thought this
part was really cool– “Standlee farm personnel scout
fields seven to eight days prior to harvest to ensure
that pests of all kinds are not present.” These three-striped
blister beetles tend to– if there’s one adult here
and there in the hay, it might not be so bad. But this insect swarms. And so if a swarm gets
trapped into the alfalfa when it’s harvested, when
it’s cut, that’s when you run into problems. So by walking the fields
right before they harvest– DAN: To make sure. DR LYDIA GRAY: Yeah. I thought that was a
really good practice. So that’s my answer
to, how can you make sure that the product
you’re feeding is quality. DAN: And to your point,
Standlee does do a great job. We do sell some of their
treats and things like that. DR LYDIA GRAY: Mhm. So if you stick with a
reputable, recognized brand, then I think you’re
in great shape.

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