Dumb and dangerous: The unusual equine journey of the bloodworm



In the latest episode of “The Parasite Journey of the Horse” series by equine parasitologist Martin Nielsen, we learn about the good doctor’s “pet parasite” — the bloodworm or Strongylus vulgaris.

“It’s the one I’ve worked with the most and I did my entire PhD on it, so I’m really excited to share this knowledge,” Nielsen says. He describes it as the “marinara meat sauce of parasites that doesn’t seem to be the smartest of the bunch”.

But this large strongyle has often been called the most dangerous parasite in horses. “It has been called ‘the horse killer’, and there is something to that,” Nielsen says. “There are some distinct lesions this parasite can cause.”

Thankfully, major problems are rare: “It is not in the interests of the parasite to kill the horse. That’s kinda stupid.”

Martin Nielsen with an example of the damage that bloodworms can do to a horse.

Speaking on the lifecycle of the bloodworm, Nielsen describes how they make their way into the intestinal blood vessels and then migrate upstream, all the way up to the aorta, which is the main blood vessel supplying the entire body, where they hang out for about four months. After that, they head back to the intestine where they produce their offspring. The whole process takes about six months.

The good news is that no resistance to bloodworm has been developed. “We don’t know if it is ever going to. Any dewormer on the shelf will work against bloodworms,” Nielsen says.

Watch the video to learn more!

• We recommend watching the series in order:
Episode 1: Foal parasites
Episode 2: Ascarids, or roundworms
Episode 3: Small strongyles (cyathostomins)
Episode 4: Bloodworms
Episode 5: Tapeworms
Episode 6: Bots
Episode 7: Pinworms

See also: the inside secrets of “Creepy Crawlies”.

» For more from Dr Nielsen, check out his short video series on parasite control, starting here.

Martin K Nielsen

Dr Martin Nielsen is a professor in equine parasitology at the Maxwell H. Gluck Equine Research Center at the University of Kentucky. » Read Martin's profile

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