Natural Horse World

Colic, Peritonitis and Worms

Finn was lucky to survive peritonitis caused by emerging encysted strongyles.

What do these conditions have in common? Colic and Peritonitis are both serious issues that require immediate veterinary treatment, and both can be caused by worms!

This is something I discovered when my 6yo Arabian stallion Finn, suffered a colic episode that also resulted in hypothermia as he went down on a cold wet day.
Thankfully, I went to his paddock again at lunchtime (the boys had been fed at around 9 am and he seemed fine) to get the trailer for re-filling with hay and found him laying down in the rain. When I got closer, I saw he was in a lot of pain so immediately gave him some rescue remedy (always carry some in the car) then raced back home for a warm rug and the stethoscope.

I took his heart rate which was up to 48bpm and allowed him to lay down as he was quiet and not wanting to roll. His 3 paddock mates all stood around us looking concerned, with the most senior gelding occasionally trying to chew on Finn to get him up.
When there was no noticeable difference in his pain levels, gut sounds or heart rate after 30 mins I called the vet who arrived within half an hour.

After checking all his vital signs he administered some painkillers and muscle relaxant then did a rectal exam which confirmed an impaction, so Finn was then stomach tubed with Parrafin oil and Tympanel to help the impaction pass.
I was very proud that he handled his first rectal exam and stomach tube without even a twitch!

Finn then seemed much better (the drugs were working) so I walked him home on the vet’s advice as movement would help the impaction shift, and with his mates following, he strode home and happily tucked into some hay in the barn with access to the yard overnight.
The next morning he was quite depressed again and not eating and after I’d fed the others, he was laying down again obviously in pain. Another visit from the vet confirmed a high temperature indicating an infection so he was treated aggressively with antibiotics for peritonitis.

He seemed to improve the next day so was moved to fresh pasture, but by the following day he was down again. This time the vet suggested worming him again (he’d been wormed 10 days prior with Panacur) this time with Equest Plus for tapeworm as they have been known to cause an impaction colic.
So we did that immediately and gave more painkillers to keep him comfortable.

So many small stongyles in one ball of manure!
So many small strongyles in one ball of manure!

The next morning he was fine and his manure was already passing a large amount of tiny hair-like worms which I believe were small strongyles. The Panacur would have been enough to kill the existing worm burden, but as I hadn’t done it for 5 days in a row, the emerging encysted strongyles caused the peritonitis and subsequent colic symptoms.
After passing that burden, he made a complete recovery thankfully – many horses get seriously ill or die if not treated correctly.

Finn may be one of the 20% of horses that carry 80% of the worms so it’s possible he had a large number of encysted strongyles that upon worming with a single dose of Panacur, emerged to take the place of the cleaned out worm population. This mass emergence would have caused both peritonitis and the impaction colic.

My intention had been to worm him with Panacur for 5 days in a row to kill any encysted strongyles, but I couldn’t get the horses to take it in their feed and dosing four strong and protesting boys with the drench gun every day for 5 days (with limited success on my own – liquid wormers are very easy to spit out), I gave up and decided to just use Equest next time they were due.

And that was my mistake as it had been exactly 12 months since they were wormed with Equest so they were overdue. I’ve since realised I should have been worming twice yearly with Equest for encysted strongyles (Dr Ann Nyland’s E-book – What You Don’t Know About Worms Will Surprise You ) gives good schedules to follow.

So what are encysted strongyles? They are a 3rd stage larvae of the small strongyle (cyathostomes) that are eaten and go into the lining of the horse’s colon and form a cyst.
This is why they are called encysted strongyles and the only chemicals that will kill them are moxidectin with a 90% success rate (in Equest/Quest wormer), and Fenbendazole in Panacur 100 if it’s used for 5 consecutive days at 10ml per 100kg. No other wormer will be able to kill them.
Encysted strongyles can stay in a horse for years (or as little as 8 weeks) before they develop into 4th stage larvae and enter the colon.

Finn feeling better.
Finn feeling better.

If there’s a huge amount of them, the emerging may kill a horse and I suspect many ‘mystery’ deaths could be attributed to them. If there are less but a lot emerging, the horse may get colic, and/or scour and/or get oedema.
So it’s vital to worm your horse at least twice yearly with Equest/Quest or Panacur (if you can get them to take it effectively) to ensure that the emerging encysted strongyles won’t harm your horse.

Also useful to know is that worm counts will not show how infested a horse is with encysted strongyles!
There is a lot more in-depth info on this in Ann Nylands book which I highly recommend to every horse owner.

To sum it up I quote from the book “Research has shown that cyathostomes (small strongyles) have become more and more important as a cause of sickness and death in horses, and today are considered the main reason for worming horses”.
If you want to save yourself a huge vet bill, and your horse from all those injections – don’t put it off! Equest is available (often at discount prices) in many online stores and is sold by most saddlery stores, rural feed stores and vets.

For more good information about encysted strongyles, read  ‘The Worm That Kills – And Why Only Two Worming Chemicals Can Stop It’.

1 thought on “Colic, Peritonitis and Worms”

  1. Wrangler Jayne

    Good, to-the-point article – thanks Cynthia. Was Googling peritonitis and it popped up, as have a student with a horse with peritonitis at the moment, so helpful for prevention strategies. Jayne.

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