Equine parasites grow, feed, and take shelter in your horse’s gut. We often see heavy worm infestation – strongyle, ascarid, pinworm, tapeworm, and bots in cases of severe neglect. Rescue organizations take in horses that show obvious signs of parasites, including a loss of weight, dry coat, nasal discharge, dehydration, and diarrhea or constipation. Not only do these horses suffer from a failure to thrive, but their guts are pressure cookers for impaction colic. You take better care of your horse, but did you know that despite his shiny coat it’s possible he’s harboring parasites, too? In this month’s Horseman’s Corner, we’ll offer tips on how to manage “bugs gone wild.”

Parasite Lifecycle

Worms begin their lifecycle in your horse’s gut where female larvae lay their eggs. These eggs are then passed through the gut and into the manure. They “drop in,” so to speak, directly into your horse’s “living room” whether that’s a stall, paddock, or pasture. If the humidity and temperature is just right, these eggs hatch and mature into larvae that are re-ingested.

Don’t be misled by their desire for favorable weather though. These bad boys survive temperatures well below freezing. If the weather is iffy, they just hold out and wait. If only we could figure a way to get horse poop to go directly to the waste treatment plant, we’d be all set. Which brings us to our next point – an effective de-worming program puts manure management first and foremost.

Manure Management  

It’s near to impossible to eliminate all worms from your horse’s environment, although it is a noble quest. What we can do is keep the bad bugs to a minimum by cleaning paddocks daily. Unfortunately we’re often foiled by the weather – one day sub-zero temps have turned our manure piles into immovable concrete towers, the next a torrential rain is washing the manure into the mud.

Cleaning paddocks is half the battle. What do we do with all that manure? We know parasites don’t mind cold and they love a warm, moist environment, but what if we raised the temps a bit? That’s where composting comes in. Managed right, the compost pile’s internal temperature reaches well over 90° Fahrenheit – certain death for most equine parasites. Better yet, composting decreases the size of your waste product by about 50% making manure easier to manage. For more info on how make and maintain a compost pile, contact your local county extension office or horse council.

Dragging pastures is another option, but only during hot and dry weather. Keep horses off newly dragged pastures for about two weeks to allow the parasites to wither and die.

Offensive Action

Prevention is key, but you’ll need to fight back in other ways as well. Consider fecal egg counts and chemical or natural de-worming products. Remember that even natural remedies can have severe side effects, especially for young horses and pregnant or lactating mares. Consult your veterinarian to set up a program that works for your horse.

Let’s start with fecal count test kits, which we believe should be in the arsenal of any good de-worming program. Some professionals are not keen on using fecal test kits. Let’s look at why that is. The fecal test kit is limited to nailing the front runners like adult roundworms (ascarids) and strongyles. Bots, pinworms, and tapeworms probably won’t be detected in the fecal test. If the test comes back negative, it doesn’t prove your horse is free of parasites. It simply shows that that particular lump of manure was free of detectable parasites. A different manure sample collected the following day might have offered a different result.

But don’t give up, the kit really earns its keep when the test results come back positive and tell us what type of infestation we’re battling. This will tell us what class of de-wormer to administer. If the test comes back negative, we’ll view that as one part of the picture, but not a complete picture. In order to get more information we’ll need to take frequent fecal counts over the course of the year, usually every three months or so. We recommend a re-check after de-worming to determine the effectiveness of your de-wormer. Many horse owners see a 90% reduction in fecal egg counts. That kind of result is worth the effort. 

Chemical de-wormers have taken a lot of flack over the years as parasites increase resistance to them. Rotational de-worming between classes (not brands) is recommended in order to kill off a variety of bugs your horse may be harboring in his gut. New evidence shows that while parasites are developing resistance to chemicals, rotational de-worming does not seem to slow that resistance. So targeting the right worms with the right drugs is still going to deliver the biggest bang for your buck.

Natural/herbal remedies abound, but it’s important to realize that most are not approved by the FDA. Still, that doesn’t mean they aren’t effective. Everything from fennel, garlic, rosemary, tansy, pumpkin seeds, and even tobacco (yes, tobacco) are used in herbal de-wormers. There have been no controlled experiments to determine their efficacy (or none that this writer can find), but many horse owners claim at least a degree of success with these products. No matter what product you use, it’s a good idea to administer a pro/pre-biotic to the horse’s gut to help protect him from the chemical assault of de-worming.

Diatomaceous earth has also been used as a de-wormer for horses, sheep, and goats, but its efficacy is still under scrutiny. The idea behind diatomaceous earth is that its abrasive qualities damage the worms by slicing and dicing their outer skin as they pass through the horse’s gut. Not a lot of research has been done to determine the effect DE has (if any) on the horse’s gastrointestinal tract.

A Word on Tapeworms

Tapeworms used to be considered rather benign, but research shows that 80% of ileal impaction colic is associated with tapeworms. Spring is the prime transmission period for tapeworms as horses graze on spring pastures. These guys attach to the inside of the ileocecal area and cause inflammation, ulceration, and possible bowel obstruction. The chemical class praziquantel has shown to be 100% effective against the tapeworm. Some manufacturers combine praziquantel with ivermectin, an effective combination, so long as the praziquantel does not fall below 1mg per kg (2.2lbs) of horse.

You really can gain the upper hand when it comes to getting rid of equine parasites. Remember to put good manure management first and always consult your veterinarian before beginning any de-worming program.

Photo: Helen Peppe