Choosing a Horse Dewormer Pack

Key Takeaways

• Horses are vulnerable to more than 150 internal parasite species, which can impair growth, performance, immunity, and lead to serious issues like colic if left untreated.
• Strategic deworming should begin with a fecal egg count (FEC) test and follow AAEP guidelines, with most adult horses treated in spring and fall based on shedding levels.
• Horses considered low, moderate, or high shedders require different deworming frequencies, with young horses and high shedders needing more frequent treatments.
• Foals face the highest parasite risk, especially from ascarids, and require a structured, frequent deworming schedule during their first year of life.
• Accurate dosing, annual FEC testing, periodic fecal egg count reduction tests, and avoiding outdated rotational deworming practices help reduce resistance and protect long-term horse health.

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There are more than 150 species of internal parasites that can infect horses, including large strongyles, small strongyles, roundworms, pinworms, tapeworms, and bots. Left untreated, these parasites can damage vital organs, stunt growth, hurt performance, and even trigger colic. For a closer look at how each parasite affects your horse, see our guide to worms in horses.

The good news: choosing the right horse dewormer pack for your horse is simple once you know their actual parasite risk. Instead of guessing at a schedule, today's best practice starts with testing and ends with a pack built for what your horse actually needs. This guide focuses on choosing the right pack for your horse's age, workload, and shedding status. For the biology behind each parasite, our Worms in Horses 101 guide covers that in depth.

Start With a Fecal Egg Count, Not a Calendar

Work with your veterinarian to run a fecal egg count (FEC) test before choosing a dewormer pack. This test measures how many parasite eggs per gram (EPG) your horse is shedding and sorts them into a risk category:

• Low shedder: 0 to 200 EPG
• Moderate shedder: 200 to 500 EPG
• High shedder: more than 500 EPG

The American Association of Equine Practitioners (AAEP) updated its Internal Parasite Control Guidelines in 2024, and the guidance is clear: deworm all horses at a baseline rate of once or twice a year, then treat high shedders more often based on their FEC results. The guidelines specifically advise against deworming every horse on a fixed schedule year round, or rotating dewormer classes without a reason to. That older approach is outdated, and it has contributed to rising dewormer resistance in parasite populations.

Once you know your horse's shedding status, a pre-built dewormer pack takes the guesswork out of timing the rest of the year.

How to Choose the Right Pack for Your Horse

A few factors, beyond the FEC result itself, help point you toward the right pack:

• Age: Foals and young horses under 5 tend to shed more eggs and need a different schedule than mature horses. Senior horses over 15 are also more susceptible and often benefit from closer monitoring.
• Workload and environment: Horses that travel for shows or training, or that live in boarding barns with more horses per acre, face more exposure from shared spaces and other horses. Nonrotated pastures raise risk too.
• Region: Warmer, humid climates support parasite activity for more of the year, which can push some horses toward more frequent treatment. Your local vet knows what's circulating in your area and can help you time doses to your climate.

None of these factors override an FEC test. They simply help you and your vet decide which pack and shedding assumption fits your horse before testing, or confirm the plan once results are in.

Comparison: Current Horse Dewormer Packs

Here's how Valley Vet's current dewormer packs line up by FEC shedding category and life stage:

Shedder Category / Life Stage	Recommended Pack	Frequency	Timing and Products
Low shedder (0 to 200 EPG)	Zoetis Annual 2X Horse Dewormer Pack	2x/year	April 1: Quest (moxidectin) Nov. 1: Quest Plus (moxidectin/praziquantel)
Moderate shedder (200 to 500 EPG)	Annual 2X Pack, plus one added Ivermectin treatment	3x/year	April 1: Quest Late spring/early summer: Ivermectin Nov. 1: Quest Plus
High shedder (over 500 EPG), yearlings, and 2 year olds	Annual 4X Horse Dewormer Pack	4x/year	March 1: Duramectin (ivermectin) June 1: Quest (moxidectin) Sept. 1: Duramectin Dec. 1: Zimecterin Gold (ivermectin/praziquantel)
Foals (2 to 10 months)	Annual Foal Dewormer Pack	4 doses in year one	2 months: Anthelcide 5 months: Pyrantel 7 months: Zimecterin Gold 10 months: Duramectin

A few multi-dose rotational packs are also available for owners who prefer a set annual rotation without an FEC test guiding it. Current AAEP guidance favors building a program around FEC results instead, so we'd recommend testing first and choosing from the Zoetis Annual 2X Horse Dewormer Pack, Annual 4x Horse Dewormer Pack, or a single Ivermectin treatment above, based on what your horse's results show.

Deworming Foals

Foals face a different set of risks. Ascarids, also known as roundworms, are the biggest concern for young horses, since they can affect a foal's developing immune system and cause respiratory issues, stunted growth, lethargy, and colic.

The Annual Foal Dewormer Pack is built around AAEP guidance and currently includes four doses across a foal's first year: 2 months (Anthelcide), 5 months (Pyrantel), 7 months (Zimecterin Gold), and 10 months (Duramectin). Because a foal's immune system and parasite exposure change quickly during that first year, timing matters here more than almost anywhere else. Work with your vet to confirm this schedule fits your foal, especially if they were born outside the typical spring foaling window.

A Few More Tips for Deworming Horses

Dose to your horse's actual weight, don’t guess. A weight tape or digital livestock scale gets you the exact number: stand the horse square, wrap the tape around the heart girth, read the closest approximation, and set the dewormer to that weight.

Run an FEC yearly for each horse. Run a fecal egg count reduction test (FECRT) annually as well, per AAEP's latest guidance, to confirm the dewormer you're using is actually working. In herds with many horses, testing six is enough to represent the group.

Skip the fixed rotation. Blindly rotating dewormer classes on a quarterly schedule, regardless of a horse's actual parasite load, is no longer recommended and can accelerate resistance. A strategic, FEC-guided program protects both your horse's health and the long-term effectiveness of the dewormers themselves.

For a deeper walkthrough of deworming questions, from timing to weight-based dosing, visit our Horse Dewormer FAQ.

Frequently Asked Questions

What's the difference between a wormer pack and a single dewormer?

A single dewormer is one product for one treatment. A wormer pack bundles several dewormers together, often with different active ingredients, pre-timed across the year so you don't have to track down the next product yourself. Packs built around FEC-based shedding categories also take the guesswork out of matching product to purpose.

How do I choose the right dewormer for my horse?

Start with a fecal egg count test from your veterinarian to learn your horse's shedding category. From there, match your horse's age, workload, and living situation to a pack built for that risk level, and confirm the plan with your vet before you start.

Are dewormer packs cheaper than buying individually?

Packs are typically priced close to, or slightly below, buying each product separately. The bigger value is convenience and consistency, since a pre-built schedule helps make sure no treatment gets missed or delayed.

How many doses are in a typical wormer pack?

Valley Vet's Annual 2X Pack includes two doses for low shedders, the Annual 4x Pack includes four doses for high shedders, yearlings, and 2 year olds, and the Annual Foal Dewormer Pack currently includes four doses timed across a foal's first year.

How often should I deworm my horse?

Most adult horses need a baseline of one to two treatments a year, in spring and fall. Horses identified as high shedders through an FEC test may need three to four treatments a year instead, which is why testing first is what determines the right frequency.

What is a fecal egg count test?

A fecal egg count (FEC) test measures how many parasite eggs per gram are present in a horse's manure. Your veterinarian uses the result to sort your horse into a low, moderate, or high shedder category, which then guides how often they need to be dewormed.

Is rotational deworming still recommended?

No. AAEP guidelines now advise against deworming every horse on a fixed schedule or rotating dewormer classes without a reason to, since that practice has contributed to rising dewormer resistance. Base your horse's deworming frequency on FEC results instead, and target extra treatments to the horses that actually need them.

Sources: American Association of Equine Practitioners (aaep.org), and Valley Vet Supply's current equine dewormer catalog.

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