Parasites are a fact of life for horses, and your horse’s lifestyle may in part determine the type of worming schedule you use. The two basic distinctions are time-based: daily worming vs periodic “purging” is the first decision horse owners make when choosing a de-worming schedule.

 

There are at least a half-dozen horse parasites, not including any regional ones that may lurk in your particular area. Horses that board or work with other horses, travel to shows or events, or graze in manure-fertilized pastures are much more likely to pick up parasites, whose eggs, larvae or host organisms are present may be eaten with cropped grass. Very young and old horses are more prone to parasites, and more easily injured (or killed) by them.

 

Your vet may recommend monthly worming for foals until weaning and then worming every six weeks until the horse is 12 months old, at which time the eight week schedule commences. Older horses may need worming every six weeks. If your horse is often exposed to others or grazes in fields where manure may be a problem, vets may recommend a daily rather than periodic worming schedule.

 

Common horse parasites include:

   

 

Daily or Periodic Schedule?

Some schedules use bi-monthly (every eight weeks) doses of wormers; on others, the wormer is added to feed: the horse gets a smaller dose of the medicine every day. Daily worming is something of a misnomer, since additional, annual or biannual wormers are used even when your horse is on a daily schedule.

 

Regular worming is a major priority, not to be put off or “forgotten” when life gets hectic. Nail a calendar (with attached pencil) to the stable wall where you can see it every day. Mark worming days in advance, along with the medication to be administered, and mark the day before each worming day to give yourself time to prepare. If you are worming more than one horse using different schedules, you can label each medication with the horse’s name and date of administration so there’s no confusion. If you need to buy the medications in batches rather than a year’s at a time, mark advance dates for ordering the various anthelmenthics.

 

Wormers and Competitions

Some worming medications can mask other medications; if your horse will be attending an event, find out what the event’s requirements are as to the scheduling and reporting of worming administrations. You may need to provide proof and dates of worming if your horse attends an event within a week of being wormed.

 

Wormer Forms

Wormers are available in paste, gel, pill or pellet and liquid forms. Powdered wormers may be mixed with water and are often administered by vets. Like all of us, horses will tend to spit out things that taste nasty to them, and most worm medicines aren’t known for delectability! So the question is, what’s the easiest way to get worm medicine into a 1,200 pound animal who’d really rather not have it?

 

If you start your foals on daily wormers after their first month of life, you may find that your horse will assume his food is supposed to taste that way. The downside of daily feed dosages is some horses may avoid eating the pellets, especially if you’ve switched a horse that hasn’t had daily worming to a new daily schedule. Pastes may be the next easiest form: liquids, being “shot” down the throat with a big syringe, may get more worming liquid on you than on your horse. If you use a paste, some vets suggest first rinsing your horse’s mouth with water, letting it drip out, then pushing in the paste. Most wormers available to horse owners come in paste form, so once you’ve developed a working system for administering them, you’re home free.

 

Vets once administered liquid wormers by stomach tube, but this should be a last resort, since it carries medical risks to the horse, vet and trainer! Naso-gastric tubing is uncomfortable at best—even painful. It’s an unpleasant method and best avoided.

 

Does My Horse Have Parasites?

If your horse hasn’t been on a proper worming schedule, he probably has parasites. A horse with worms looks sick: the coat will be dull, there may be digestive problems such as colic, and a distended belly. Pinworms can cause tail rubbing and hair loss (as well as weight loss). For a horse with parasites, performance will be poor and the attitude listless. There may be bleeding, as some worms cause ulcers, dental problems and arterial damage. Large strongyles can damage the brain, lungs and heart; small strongyles injure the digestive tract. Bots can perforate the walls of the stomach and cause dental disease, and tapeworms can cause ulcers in the large intestine.

 

If you suspect your horse is suffering from parasites, even if you’ve been using a worming schedule, consult with your vet. He or she may recommend a fecal egg count, to determine the level of parasite infestation in your horse. You may want to schedule an annual fecal count, a couple of weeks after worming, to make sure there’s nothing you’ve missed.

 

One more item to keep in mind. Not all medications cover all parasites, although a few, such as ivermectin, fenbendazole and moxidectin do cover several types.  Most vets recommend a rotating schedule of wormers, to catch all the possible worms at the best possible time. Your vet can create a simple rotation schedule to help you keep parasites under control, considering factors like the weather and environment, your horse’s lifestyle and state of health and maybe even the robustness of your pocketbook.

 

An overview of parasites and the chemicals that kill them.

 

 

 

 

 

(Moxidectin kills bots and encysted small strongyles and provides 84-day suppression of strongyle eggs.)

 

 

 

 

 

 

 

 

Jeffrey Rollo, of Alphahorse.com, created the following worming schedule. If you’re feeling overwhelmed by starting a new schedule, you can work your way into it gently by following this simple rotating schedule. Jeffrey also recommends adding a five-day double-dose schedule of a Fenbendazole-based wormer in October and February for horses that graze on a frequent basis.

 

**Moxidectin is NOT recommended for foals or weak horses since an overdose can be very dangerous to them.