Things that fly, bite and bother your horse are in the air, and in the gut. Whether you board your horse or have your pony at home, now is the time to think about parasite control for horses to protect your equine friend from pesky pests like worms and flies before they cause problems.

Fly Control

As the weather warms, flying insects of all kinds start to emerge at the barn. You may notice your horse start to swish his tail on a calm day in the pasture or nip at his flank while you’re on a trail ride. Not only are flies annoying, but they can also irritate your horse’s skin and spread disease. Learning how to manage flies early in the season means you’ll be a pro at fly control by summer when they are even more of a menace.

The first step in effective fly control is good barn hygiene. Make sure manure is picked up in the barn aisles and stalls are cleaned daily. Also keep fresh water in your horse’s buckets. Manure and stagnant water are prime breeding grounds for bugs that bite, including mosquitoes.

Next, don’t fear the fly spray. As a horse sweats, sprays wear off, so a good routine is to spray your horse in the morning and in the evening, and before you ride. Don’t forget to re-apply if you bathe your horse.

Hold the spray about 6 inches away from your horse’s body and apply up and down his legs and under his belly and up the neck. Face application is important, too, but be careful. Many horses don’t like to be sprayed in the face, so applying spray to a clean cloth and wiping your horse’s ears and around his eyes is better, especially so spray doesn’t accidentally get in the horse’s eyes. There are also fly wipes specifically made for this. A fly sheet and fly mask may also be a solution if your horse has sensitive skin.

Finally, don’t forget about the secret weapon against flying insects: a good breeze. Wind makes it impossible for flies (and mosquitoes) to land on your horse, and no landing means no biting. If your horse’s stall has a window, open it when possible. A fan in the stall or in the barn aisle can also be a huge help in preventing pests from bothering your horse (make sure to use a fan rated for farm or industrial use so the motor is sealed off from dust and there is less risk of fire).

Parasites

Internal parasites, also called worms, are common in horses because immature worms (larvae) live on blades of grass and are passively eaten when a horse grazes. Larvae emerge in pastures in the spring. These larvae then develop into adult worms within the horse’s intestines.

While this sounds gross, it’s really important to realize that a small number of worms typically does not harm a healthy adult horse. However, large worm infections can cause problems, like diarrhea, weight loss and sometimes colic.
Equine parasite control can be done with one of several deworming drugs made for this purpose, but not all horses need to be treated. So how do you know if your horse needs a dewormer?

In the spring, ask your vet to do a test called a fecal egg count. To do this, your vet will take a sample of your horse’s manure, mix it with a special liquid, and look at the sample under a microscope. Parasite eggs are shed in your horse’s manure, so if your horse has worms, their eggs are seen as small oval shapes under the microscope.

Don’t worry if your horse’s manure is positive for eggs; this is very common. What’s most important is the number of eggs. Your vet will count them and tell you how many she finds. If there are many eggs—typically over 200—your vet may recommend treating your horse with a dewormer.

If there are fewer eggs, this indicates a mild infection, and your horse typically won’t need treatment unless he is young or otherwise sick. Not overusing dewormers helps prevent the development of resistance by the parasite to these important drugs.

To help control worms on the farm, remove manure piles in small pastures and paddocks to prevent the spread of worm eggs. Not allowing your horse to overgraze a pasture is important, too. Grass should be kept about 3 to 4 inches tall—shorter than that and it’s time to move your horse to another field, if possible, to allow the grass to re-grow.

With a little planning and awareness, you and your horse can be worry-free from worms and flies this spring!

This article about flies, worms, and more appeared in the Spring 2020 issue of Young Rider magazine. Click here to subscribe!

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You’ve learned to use fecal testing and you know horses should be dewormed according to their individual needs, and not all be on the same program. But if you haven’t added a daily horse dewormer to your program, you could be overlooking a way to provide continuous protection against many equine parasites.

The paste dewormer you administer occasionally is considered a “purge” dewormer. These products are designed to interrupt the infestation cycle of parasites and kill them.

A daily horse dewormer is different in that it’s designed to create a barrier to parasites before they cause infestation.

“A barrier dewormer is probably the best way to protect an individual horse against parasites,” says Tom Kennedy, Ph.D., a veterinary parasitologist based in Westport, Wisc.

Daily dewormer products protect against as many as 18 species and stages of equine parasites, including pinworms, adult large strongyles, adult small strongyles and their fourth-stage larvae, and adult ascarids and their fourth-stage larvae.

“Daily dewormers work against the bulk of parasites we’re concerned with in horses, especially strongyles, which are the parasites of greatest concern with adult horses, and ascarids, the biggest issue with foals and young horses,” says Kennedy.

How it Works

Pyrantel tartrate, the standard anthelmintic (deworming) drug used in daily deworming products, has a wide margin of safety and can be used on horses of all ages, from foals to seniors, including pregnant and nursing mares.

“Pyrantel tartrate is not well absorbed by any mammal; it passes through the horse,” says Kennedy.

Whether a grazing horse picks up parasite eggs or larvae, a daily horse dewormer product begins working on the parasites in larval form once they’re in the horse’s digestive tract.

“We’re basically using the horse as a ‘mixing vat’ to expose the larvae to the drug, mixing the dewormer into the gut contents of the horse,” explains Kennedy. “When the larvae are picked up by the horse or the larvae come out of the eggs the horse has picked up, they start to metabolize, picking up nutrients in the horse’s gut. The dewormer is present and starts working on the parasites wherever they’re having their normal growth process. With strongyles, much of this happens in the large intestine. With ascarids, it happens in the small intestine.”

The drug works directly on the neuromuscular system of parasite larvae to paralyze them, then they pass out of the horse’s body in the manure.

Getting Started

Talk to your veterinarian before starting a daily horse dewormer. Your vet may recommend first administering a broad-spectrum dewormer, such as ivermectin, to get rid of any worms that may already be in the migration cycle.

“Over the years, I’ve recommended daily dewormer for many of my clients,” says Sam Crosby, DVM, who has worked as sales veterinarian at Heritage Place sales facility in Oklahoma City since 1995 and maintains his own equine practice in Arcadia, Okla.

Crosby says daily dewormers have been an effective tool for clients with horses that still seem to have parasite problems despite being on a traditional deworming program. He advises using an ivermectin paste dewormer before starting on daily dewormer.

Read the directions on a daily horse dewormer and you’ll see it’s fed according to weight. Use a weight tape to get a good approximation of how much your horse weighs.

Because a daily dewormer is mixed with the horse’s grain ration, if you want to use it on foals, they need to be consistently eating their own feed.

Take the “daily” part of the name seriously, advises Kennedy. “You have to use it every day. It’s a barrier dewormer, and a break in the barrier [by skipping a day or more] can allow worms to develop.”

Even when you faithfully use a daily dewormer, that doesn’t mean you’ll never have to use a paste dewormer again, since daily dewormers aren’t effective against all species of equine parasites. For example, if your horse is exposed to bot flies or tapeworms, you should treat him with a purge dewormer labeled effective against these parasites at least once a year.

More Than One Tool

“Controlling parasites in horses is about management; it’s not just about one tool. You need to use them all,” says Kennedy.

An effective parasite control plan includes:

◆ Manure and pasture management

◆ Fecal testing

◆ Purge dewormers (as indicated by fecal testing and veterinarian recommendation)

◆ Daily horse dewormer
You may be inadvertently contributing to horses getting reinfected by parasites if you don’t properly manage turnout areas and pastures. Strongyle eggs pass in the horse’s manure, and once those larvae hatch, they can be picked up by grazing horses, continuing the cycle.

Keep your horse’s environment as manure free as possible to help limit parasite infection.

◆ Don’t feed hay on the ground.

◆ Don’t spread stall waste on pastures currently used for grazing.

◆ Don’t drag fields to spread manure if you currently use them for turnout or grazing.

If you must drag, only do so during hot, dry weather (not cool, wet weather), then keep horses off the field for at least two weeks, preferably four.

This article about daily horse dewormer appeared in the March 2021 issue of Horse Illustrated magazine. Click here to subscribe!

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Tiny creatures certainly have the ability to make our lives, as well as the lives of our horses, miserable. While we can never completely eliminate pests such as flies and parasites, we can do a lot to keep them at bay—especially when the weather starts getting warmer in the spring and we plan our spring horse care strategies. Let’s look more in-depth into the pests that plague our horses and what we can do to manage or eliminate them.

Pesky Flies

The flies that most horse owners deal with are the big four: stable flies, face flies, bot flies and horse flies. The best way to reduce the number of flies that annoy your horse is to make it hard for them to reproduce. Implementing fly-control methods in the spring will pay off come summer when fly populations are at their highest.

Knowing where these flies start their lives will help you put a stop to their reproductive cycle.

STABLE FLIES: These nasty greyish-black flies have a painful bite that they inflict on horses, most often on the legs. They lay their eggs in rotting vegetation, dirty bedding, manure and areas of urine.

FACE FLIES: These small, dark flies don’t bite, but instead feed on the moisture in the corners of a horse’s eyes, on the moist part of the horse’s nose and on open wounds. They lay their eggs in manure.

BOT FLIES: Unlike most other flies, bot flies do not bite or feed on the outside of the horse. Instead, they lay their eggs on the horse’s legs, shoulders or mouth with the intention of the horse swallowing the eggs.

Once inside the horse, the eggs hatch and the larvae burrow into the horse’s stomach, where they do damage for several months before passing out through the manure and continuing their life cycle.

HORSE FLIES: You can’t miss one of these flies when it lands on your horse. Horse flies are large with a black body and a white head. They prefer to leave their painful bite on the withers or rump and will easily draw blood.

Their breeding place of choice is damp soil near irrigation ditches, lakes and rivers.

Getting Fly-Free

Given the reality of how these pests live their lives, what can you do to minimize the number of flies that harass your horse? Plenty!

Here’s how to reduce pests at the barn.

MANAGE MANURE: It’s obvious that with the exception of the horse fly, the most common flies to bother horses spend their entire lives in the stable environment. Stable flies, face flies and bot flies all need manure to reproduce, with the stable fly also branching out into dirty bedding.

This is why frequent stall cleaning and manure removal is key when it comes to keeping flies to a minimum. Picking up and disposing of manure and soiled bedding every day is a must if you want to make your barn inhospitable to flies.

PHYSICAL PROTECTION: You can keep your property clean, but you don’t have much control over how your neighbors manage their manure. If you’re boarding your horse, you’ll discover that large numbers of horses make it a lot harder to control fly populations.

In both of these situations, you’ll need to provide your horse with physical protection from flies. Start by using a fly mask to keep face flies out of your horse’s eyes. A fly sheet for your horse’s body and fly wraps for his legs will keep insects from being able to reach his skin.

SPRAYS AND TRAPS: Repellent in the form of fly sprays, wipes and mists can also help keep flies off your horse. You can apply fly repellents topically to your horse daily or install an automatic misting system in your barn that will provide a dose of repellent at regular intervals.

Fly traps can also be helpful because they capture flies that are buzzing around, stopping them from annoying your horse and reproducing in your horse’s manure and bedding.

BIOLOGICAL CONTROLS: A natural way to help control fly populations is with beneficial insects that feed on fly larvae, killing the maggots before they turn into flies. These tiny wasps don’t bother horses, but they will dine on developing flies.

You can buy these fly parasites through mail-order services, placing them outside in your stabling area when they arrive each month. You’ll need to start adding fly parasites to your stable soon in order to head off the fly explosion that starts in the spring.

FEED-THROUGH FLY CONTROL: Equine feed supplements designed to keep fly eggs from hatching in manure can be helpful in keeping fly populations under control. These products work by disrupting the fly’s development cycle in the manure with the use of an insect growth regulator (IGR). The IGR passes through the horse’s system into the manure, where it prevents the fly from developing. Feed-through fly control works best if all horses on the property are given the product on a daily basis.

Spring Horse Care Against Internal Parasites

The other common creepy crawlies that can make life difficult for horses and their owners are worms. A handful of these internal parasites are a real nuisance and are prevalent among domestic equines. These pests enter the horse’s body through the mouth and complete their life cycle in manure. Infected horses can become very sick if worms are allowed to go unchecked.

The most common worms to affect horses are strongyles (large and small), roundworms, pinworms and tapeworms.

LARGE STRONGYLES: Large strongyles are only a half-inch long, but they can wreak havoc on a horse’s intestines. They can cause colic, as well as blood vessel and organ damage.

SMALL STRONGYLES: Small strongyles burrow into the intestines of the horse and cause damage to delicate tissues. They are very common in horses and can result in colic, diarrhea and weight loss.

ROUNDWORMS: These nasty worms can grow up to a foot in length. They live in the horse’s digestive tract and cause colic and poor condition. They are most common in young horses less than a year old. Older horses usually develop an immunity to roundworms.

PINWORMS: Pinworms are about 2 inches long and live in the horse’s rectum, where they may cause irritation and discharge. Horses infected with pinworms often rub their tails against fences and trees.

TAPEWORMS: You can help get rid of the worms in your horse’s body by using a dewormer every few months. These products are available in tack and feed stores, but should be given under the guidance of your veterinarian, because some worms are developing resistance to the most common dewormers. Your vet can help you rotate the different types of wormers to help prevent this.

Fecal egg testing involves having your horse’s manure tested every few months for parasite eggs. This technique is becoming the preferred method by many veterinarians for parasite control.

Because the weather is getting warm, spring is a great time to start your spring horse care strategies against parasites, as well as flies. A number of mail-order laboratories provide this service, which requires you to send a small manure sample for testing. The resulting fecal egg count helps determine if your horse has worms, and which species, so you can effectively treat the infection with an over-the-counter dewormer.

You can do a lot to help prevent worms from taking hold of your horse by maintaining good manure control at your stable. Pick up manure and soiled bedding frequently, and keep water troughs and feeders clean.

Starting good stable hygiene in your spring horse care plan is the best way to keep both flies and parasites under control throughout the year. Your horse will thank you for it.

This article on spring horse care on preventing parasites and flies appeared in the March 2020 issue of Horse Illustrated magazine. Click here to subscribe!

Further Reading on Spring Horse Care

• New Fly Products for Your Horse
• Understanding Fly Control Labels
• 7 Fly Control Myths
• April 2020 SmartPak SmartTip of the Month: Controlling Flies from all Angles
• Regional Parasite Control for Horses
• Why Dewormer Rotation is Over
• Spring Horse Care Checklist

The post Protecting Your Horse This Spring from Flies and Worms, Oh My! appeared first on Horse Illustrated Magazine.

Each season change brings its own set of challenges and opportunities. Here are the most important checkpoints to carefully consider this fall for care of your horse before the snow and ice arrive to make life harder.

Hoof Care

Fall is the best time of year for the hoof,” says Brandon Hickman of Hickman Farrier Services in Signal Mountain, Tenn. “Depending on the weather, the nutrients taken in during the spring and summer months are now reaching the hoof. I often see that, for most horses, the hoof wall is better in the fall. Nature seems to be preparing the hoof to be as strong as possible for the approaching colder weather.”

Hickman offers the following hoof care advice for fall.

Inspect Pastures: Closely monitor pastures that include or are near wooded areas. Some species of trees produce acorns, nuts and fruits such as apples and pears at this time of year. While many horse owners already know that laminitis and founder caused by grass are of particular concern, they don’t realize that a horse can also founder, or at the very least colic, from overeating these foods.

Trimming & Shoeing: The hoof tends to grow a little more in the fall. In order to avoid problems down the road, it’s important for owners to be diligent about scheduling trims, resets, and/or new shoes.

Correct issues early. Just as important as routine hoof care, now is the time to make sure there are no problems, and if you find any, to correct them. It’s critical to monitor your horse’s hooves for issues such as cracks, white line disease, and thrush.

A wet fall can increase the frequency of thrush. Then, as the weather gets colder, horses are being ridden less and are sometimes even turned out for the winter, resulting in less movement for the horse. By its nature, exercise generates movement, and movement grows hoof. It can be more difficult to correct issues when the hoof isn’t growing as much.

Fall is a great time to examine your horse’s vaccination protocol, especially if buying a new horse with unknown disease history, introducing a new horse into your herd, or after an extended mosquito season.

Don’t necessarily pull shoes. Abruptly pulling shoes with the change of the seasons can create temporary soreness for your horse. If you decide to do so, using hoof boots while riding can help alleviate the problem. Still, as the ground begins to freeze in late fall or early winter and your horse lacks the protection offered by shoes, there will be a period of time while he becomes accustomed to the change when he could be uncomfortable.

However, if your horse is already barefoot, it’s OK to leave him that way. Some horses need shoes year-round, but for others, keeping them on can be a matter of personal preference, according to Hickman.

Preventive Fall Horse Care

Nathan Voris, DVM, is associate director of equine technical services for Zoetis. He echoes Hickman’s sentiments that fall is one of the best seasons for horse health. He recommends the following preventative care strategies.

Vaccines: Every horse should receive an annual equine influenza and rhinopneumonitis vaccination, but vaccinating above and beyond this for the fall booster season has special considerations.

For example, horses who are traveling or live with horses who are traveling should receive semi-annual vaccinations. Horses living in areas where flooding is prevalent should be vaccinated against leptospirosis. If there is risk of exposure, horses should be vaccinated against strangles.

When thinking about horse care, fall is also a great time to examine your horse’s vaccination protocol, especially if buying a new horse with unknown disease history, introducing a new horse into your herd, or after an extended mosquito season.

Vaccinations can be administered year-round. Even late in the year, it’s not too late to administer booster vaccines or vaccines that may have been missed during the spring, such as West Nile virus and Eastern and Western equine encephalomyelitis.

Deworming: Every horse that has access to pasture should be treated against tapeworms, but don’t simply follow the calendar and deworm on the first day of fall. While this is a good general recommendation, the best defense against tapeworms is to deworm at the end of the grazing season, whenever that happens to be for your area of the country.

Tapeworms are transmitted by a horse passing eggs in his manure that are eaten by a type of mite. The eggs develop into larvae within the mites, which are picked up off the grass and eaten by the horse, allowing the larvae to develop into adult tapeworms.

During cold weather, the mites burrow into the ground and are less likely to be picked up by the horse, creating the right conditions to deworm against them. In more temperate climates, deworming against tapeworms could also be considered as part of an end of winter or early spring health routine.

In addition, most adult horses will require one to two treatments per year for small strongyles, and the fall is a good time to do this.

Dental: Because hay will be your horse’s primary food source and large-intestine fiber fermentation provides an important source of warmth, now is the time to schedule a dental exam, particularly if one was missed in the spring, to make sure teeth are functioning well.

It can also be a good time for a general checkup, especially for horses of an advanced age. During the veterinarian’s visit, be sure to discuss any dietary or other concerns you may have so you can prevent problems before they start.

The fall, however, is not the best season to run certain types of diagnostic tests. For example, if you have concerns that your horse may have developed Cushing’s disease, also known as pituitary pars intermedia dysfunction (PPID), false positive results are frequently observed when testing is done during the fall. This type of test is best performed during the spring or summer when daylight cycles allow for more accurate results, says Voris.

Nutrition

Rhonda Hoffman, Ph.D., professor and director of horse science with Middle Tennessee State University, recommends a monthly rather than a seasonal assessment of dietary needs for most horses. She offers the following guidance.

Assess Weight: Rather than simply visually assessing your horse’s weight, body condition scoring using the Henneke scale of 1 (emaciated) to 9 (obese) offers a quantitative method of doing so.

A score of 5—ribs are easy to feel but can’t be seen—is optimal at anytime of year. If your horse is a 4, you will be able to see a hint of ribs. Some older horses fall into this category and may not have enough fat cover going into the winter months to stay warm. In this case, it will be helpful to look at ways to begin putting weight back on.

On the other hand, a horse that is a 6 or 7 and slightly overweight is not a huge concern just before winter sets in. However, one that scores an 8 or a 9 will need to have the unhealthy excess pounds addressed with diet and exercise, regardless of season.

Underweight horses should be fed the best quality hay possible, and good pasture if available. Hay cubes or alfalfa can help to supplement issues with hay quality.

High-calorie grain mixes can also be added to or increased in the diet. Your local agriculture extension agent or feed sales representative can offer advice on what and how much to feed for weight gain. Fat supplements are another option if you prefer not to feed grain.

Weight tapes can aid you in monitoring your horse’s weight, and they work well for stock-type horses and small Thoroughbreds. However, there is a greater margin of error when using them for Minis, draft-type, or warmblood horses.

Hoffman also recommends the Healthy Horse smartphone app. Using a fabric measuring tape and the app, you can get a fairly accurate weight assessment, regardless of type.

Evaluate Hay Supply: It’s essential to assess how much hay your horse will need to get through the season. To roughly calculate how much you’ll need, keep in mind the average horse consumes approximately 600 pounds of hay per month during the winter.

According to Hoffman, you should start feeding hay as soon as pasture quality declines or becomes insufficient to meet nutritional demands.

Further Reading

• Fall Riding and Horse Care
• Fall Forage for Horses
• What Fall Cleanup Means on a Horse Farm
• Why Senior Horses Need Fall Dental Check-Ups
• Preventing Fall Founder

This article about fall horse care originally appeared in the November 2019 issue of Horse Illustrated magazine. Click here to subscribe!

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Social media platforms are lighting up about a recent Australian study on the possible antiviral effects that the drug ivermectin may have on COVID-19. However, there is little known about the effects this treatment could have.

Ivermectin Not Recommended for COVID-19

Soren Rodning, an Alabama Extension veterinarian, warns that people should not buy animal ivermectin products to self-medicate.

“There’s still a lot we don’t know about how effective a treatment of ivermectin really is for COVID-19 in humans,” said Rodning, who is also an Auburn University associate professor of animal sciences. “What we do know for certain is that animal formulations of ivermectin are NOT recommended for human use.”

Rodning said the Food and Drug Administration requires labels on animal ivermectin products warning people not to ingest it.

“The concentration of ivermectin in these products or some of the inactive ingredients used in animal formulations may not be safe for human use,” he said. “Specifically, these have not been proven safe for use by people through clinical drug trials. Bottom line—do not self-medicate with animal ivermectin products. I cannot emphasize this enough.”

Rodning said people commonly use ivermectin as an anti-parasitic treatment in cattle, swine, sheep, goats, horses, and pets, such as dogs and cats.

“Developed in the 1970s, the drug is also used to treat a variety of human parasitic diseases, especially in developing countries,” Rodning said. “For example, it is currently used to treat a parasitic disease caused by roundworms that affects an estimated 30 to 100 million people worldwide.”

In Vitro vs In Vivo

The Australian research circulating through social media conducted the study in vitro. “In vitro means the research was performed outside of a living organism, such as in a petri dish,” Rodning said. “In vivo is conducted on a living organism, such as mice, rabbits, or people.”

Drug trials for infectious diseases typically begin in vitro. Compounds that demonstrate positive effects then progress to in vivo studies.

“One frustrating reality for researchers is that many drugs may show in vitro effects, but not show the same type of results once in vivo testing begins,” he said.

Ivermectin in recent years has shown to have antiviral activity against a broad range of viruses in vitro.

“Most notably, ivermectin has shown in vitro activity against Zika virus and dengue virus,” Rodning said. “But so far, ivermectin has shown no antiviral effects against Zika virus in mice.”

Rodning said a human clinical trial in Thailand used the drug against the dengue virus, but it observed no clinical benefit in that research.

“There is reason to hope that ivermectin could prove useful against COVID-19, but much more research needs to be done,” Rodning said. “We are just not there yet.”

How to Fight COVID-19

Rodning said the best defenses are the simple steps already in place.

◆ Practice good social distancing
◆ Wash hands frequently
◆ Keep hands away from face, especially nose and mouth
◆ Eat a healthy diet
◆ Get adequate rest

More Information

Alabama Extension has the content piece Ivermectin Unproven as Treatment for COVID-19 that goes into greater detail about this study. For more information on the coronavirus and how it affects you, visit www.alabamaready.info or the Alabama Extension website, www.aces.edu.

Complete COVID-19 Coverage

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If you answered, “Within the last six to 12 months to see how my deworming program is working,” congratulations. You’re paying attention to current recommendations.

If you answer, “Why on earth would my horse need that?” odds are your deworming plan needs updating.

However you answered, read on to learn what you’re doing right and what adjustments need to be made to keep your horse healthy and parasite-free with a deworming plan suited to your regional climate and individual horse.

The Link to Grazing

It might have been convenient in the “old days” to deworm every horse in the barn at the same time with the same product, but remember, that’s what got us in trouble with resistance. (See “Why Dewormer Rotation is Over” for the explanation.) So how do you know when your horse needs deworming—or if he doesn’t?

For owners whose horses have access to grazing, it may help to think of it this way: time on pasture = parasite exposure.

“The longer horses are on pasture, the more they are exposed to strongyle and tapeworm infection,” says Martin Nielsen, DVM, Ph.D., Dipl. ACVM, associate professor and equine parasitologist at the University of Kentucky Gluck Equine Research Center and co-author (with Craig Reinemeyer) of the Handbook of Equine Parasite Control.

“Climate has a huge effect on parasite transmission patterns, as it affects the duration of the grazing season and defines periods of high strongyle infection pressure,” he says. “In some areas, the grazing season may be just four to five months long, while other regions allow horses to be turned out on pasture year-round.”

Consider the grazing season in your region. All horses should be dewormed at the beginning and end of that season, or in other words, at least two times per year.

Some horses (the “high shedders,” who shed more strongyle eggs in their manure than the “low shedders”), will need additional deworming treatment during the grazing season, particularly in regions where that time period is lengthy or year-round.

“If [grazing season] is six months or less, the high shedders could get one additional treatment in the middle of the season, making it three treatments total,” says Nielsen. “In case the season is more like nine months long, perhaps add one more—but only for the high shedders.”

The Trouble with Fecal Egg Testing

Fecal testing is currently the most accurate way to detect the presence of adult strongyles and roundworms, two of the most common parasite species. However, fecal tests aren’t reliable when checking for tapeworms, bots or pinworms.

Tapeworms pass their eggs in tiny packets called proglotids. In dog and cat feces, these little bags full of tapeworm eggs look like grains of white rice. In horses, we don’t usually see intact proglotids because they tend to break up and the eggs disperse before the horse passes manure.

Researchers have proposed blood and saliva tests to check titers and determine if a horse is “positive” for tapeworms. Since such testing is not widely available for horse owners, general recommendations for treating a horse for tapeworms are based on his potential exposure, which includes region and exposure to pasture. Horses in a stall or dry lot have far less exposure than horses on pasture, but there is still some risk.

Generally speaking, the best time to treat for tapeworms is in the fall, although two treatments per year might be needed in some regions. This requires a dewormer containing praziquantel or pyrantel pamoate, as these active ingredients are effective against tapeworms. In arid climates or when horses have no access to grazing, tapeworms may not be a problem.

Bots are not detected in fecal tests either. Their yellow eggs are easily spotted after female bot flies lay them on the ends of the hair, typically on the horse’s front legs and shoulders. Egg presence is an indication to deworm your horse with a product containing an active ingredient (ivermectin, moxidectin) that’s effective against bots.

Pinworms won’t show up in a fecal test, but horses infected with them often show obvious signs of tail rubbing due to itching caused by these parasites. When treating, be aware that pinworms have shown resistance to ivermectin and moxidectin.

The Non-Grazing Horse and Parasite Control

The vast majority of parasites infect horses when they graze, so what about horses who have zero access to turnout on grass?

“Some clients insist on deworming because they’ve been told they have to, but once people understand parasite lifecycles, they realize it’s really hard for horses to get parasites in a place like Southern California,” says David Ramey, DVM, whose practice, Ramey Equine, has been based in the Los Angeles area since 1984.

“Horses here live in confinement situations where they never see any grass and their manure is removed once or twice daily, so it’s extraordinarily difficult for [pasture- borne] parasites to reproduce in this environment,” Ramey continues. “[Horses] poop onto desert sand where manure bakes in the sun and is picked up and removed anyway.”

When he sees a new horse or an existing client moves a horse in from another region, Ramey recommends a fecal test to get a baseline for parasite egg presence. “If the fecal test reveals parasites, we deworm,” he says. “From then on, we do fecal tests twice a year, and if they don’t have parasite eggs, we don’t deworm.

Because parasite resistance to deworming drugs is a real problem, Ramey encourages horse owners to use fecal tests, only deworm as needed, and to use management practices that reduce the chance of parasite infection, including daily manure removal.

“Climate has a huge impact,” says Nielsen. “In a state like California, some areas have very arid conditions and limited access to pasture. This means that pasture-borne parasites, such as strongyles and tapeworms, are less prominent, and in some areas they are no longer the main target parasites.”

Although horses without access to grass don’t have a “grazing season,” the American Association of Equine Practitioners (AAEP) guidelines recommend a baseline foundation of one, or possibly two, treatments per year be given to all horses. Your veterinarian can determine the best time for those treatments if your horse has no grazing season.

Nielsen explains that these recommendations are primarily to keep large strongyles from re-emerging as a problem.

“We have seen tremendous increases in the prevalence of Strongylus vulgaris in countries like Denmark and Sweden, where a large proportion of horses never or rarely get dewormed because of a tight administration of prescription-only restrictions,” says Nielsen.

He adds that another valid reason for baseline treatments are stomach worms, Habronema, which will not show up in fecal tests. Flies are responsible for the transmission of Habronema, so stomach worms can occur in arid places, like California, even in horses that aren’t on pasture. Flies deposit the larvae on wounds, as well as other moist areas, such as the horse’s lips, nostrils, et cetera. The larvae can create so-called summer sores: oozing, expanding infections that are tough to heal and tend to reappear.

Make Your Parasite Control Plan

“Bottom line, you have to adjust to the climate you’re in, how horses are kept there, and formulate a deworming plan based on that,” says Ramey.

The good news is, you’re not in this alone. Work with your veterinarian, use fecal testing to determine which dewormers work for your horse, deworm only when needed, and while you’re at it, keep your horse’s environment as manure-free as possible.

You’ll be doing your part to not increase parasite resistance and keeping your horse healthy at the same time.

Get familiar with the latest recommendations covered in “Internal Parasite Control Guidelines” from the American Association of Equine Practitioners, which can be found at www.aaep.org.

This article originally appeared in the April 2019 issue of Horse Illustrated magazine. Click here to subscribe!

The post Regional Parasite Control for Horses appeared first on Horse Illustrated Magazine.

Unfortunately, there are plenty of horse owners still following an outdated program (from the 1960s!) of deworming by rotating products and treating their horses every two months or even more often. There’s more to worry about here than simply wasting money on excessive treatments. Here is an insight on why dewormer rotation is over and how parasites are becoming resistant to them.

Over time, overuse of dewormer allowed parasites to develop a tolerance for the drugs. Some parasites were killed, of course, but those that weren’t had better immunity to the deworming drugs, resulting in a parasite population that is becoming increasingly resistant.

We are now seeing widespread resistance to deworming drugs, particularly in the case of small strongyles, one of the most common equine parasites. Roundworms (ascarids), common in young horses, are also showing resistance. Because we only have three classes of deworming drugs available at this time, resistance is a serious issue, as it limits the available options to control parasite populations.

At present, fecal egg count reduction testing (FECRT) is the only method to detect resistance in strongyles, so it should figure into every horse’s deworming program. Your veterinarian can explain how and when to perform this simple test—and discuss the results with you so you know that you’re deworming properly.

Guide to Dewormer Resistance

Resistance among the following common parasites is cause for concern.

Small Strongyles

• Widespread resistance to fenbendazole, oxibendazole
• Resistance to pyrantel pamoate
• Emerging resistance to ivermectin and moxidectin (also referred to as macrocyclic lactones)

Large Roundworms (ascarids)

• Some resistance reported to fenbendazole, oxibendazole, pyrantel pamoate
• Widespread resistance to ivermectin and moxidectin (also referred to as macrocyclic lactones)

Pinworms

• Resistance to ivermectin and moxidectin (also referred to as macrocyclic lactones)

Tapeworms

• No resistance currently reported, but because there are no good resistance tests available for tapeworms, resistance could well be present.

Read more about Regional Parasite Control for Horses >>

This article originally appeared in the April 2019 issue of Horse Illustrated magazine. Click here to subscribe!

The post Why Dewormer Rotation Is Over appeared first on Horse Illustrated Magazine.

1. Spring vaccines. One of the first spring horse care tips is to vaccinate your horses. These are the most essential spring items for many horse owners. But do you know what vaccines your horse needs? The American Association of Equine Practitioners has a complete list of core vaccines every adult horse in the US should receive on a yearly basis. These include rabies, EEE/WEE, West Nile Virus, and tetanus. If you plan to travel with your horse to shows or trail rides or other events where he might have contact with other horses, your horse should also receive “risk based” vaccines for common contagious diseases such as equine herpes virus and influenza (often a combo vaccine called rhino/flu) and strangles. Other vaccines such as Potomac Horse Fever and botulism are geographically dependent but are still annual necessities if your horse resides in an endemic area.
2. Coggins. The next spring horse care tip is to get a Coggins. If there is the potential for your horse to travel over state lines or attend a show or organized trail ride, he’ll need a Coggins test. This blood test tests for a disease called Equine Infectious Anemia (EIA). Depending on where you live and the functional capacity of your closest state laboratory, getting your horse’s Coggins results could take a week or more. Including a Coggins test with the vet visit for spring vaccines is a convenient way to get everything done at once. Your horse’s results will come back to you in paper form. Keep this safe and accessible when you travel with your horse.
3. Physical exam. When your vet comes for spring vaccines and a Coggins, have her assess your horse’s overall health. Have you noticed any lumps or bumps since your horse has shed his winter coat? Do you have any worries about his athletic conditioning, a minor nagging lameness, or any behavioral issues? This exam is a great time to ask your vet these questions to make sure you’re starting the busy season off on the right hoof. It’s also a great time to weight tape your horse so you get a feel for his body condition. Fecal checks for parasites can also be done at this time, and depending on the results, a deworming, too.
4. Hoof care. Before you start logging those serious miles in the saddle, having your horse’s hooves in tip-top condition is imperative. If your horse has been barefoot all winter but increased spring training requires shoes, now’s the time to get his feet trimmed and accustomed again. A good trim and balancing can also help clear out those mushy frogs and gunky soles from all that wet slop of leftover snow and springtime showers.
5. Dental care. Spring is a great time to schedule your horse’s routine dental floating. Many adult horses only need a dental check and rasp annually in order to keep any sharp points in check. (Senior horses frequently require dental floating twice a year.) This is a good time to mention if you’ve noticed your horse demonstrate any head shaking or fighting the bit, which may be indications of dental pain.
6. Pasture management. Spring is synonymous with rain and the resultant sudden growth of everything green, especially grass. While lush green pastures appear pleasing to the eye (and make your horse’s mouth water), the threat of laminitis due to the over-consumption of rich pasture is very real. Now is the best time to have your pasture management strategy in place. If your horse is on pasture, do you need to control his grass intake? If so, how? Strip grazing, limited turnout, the use of dry lots, and grazing muzzles are all good methods for preventing spring laminitis.
7. Barn management. Spring-cleaning most definitely applies in the same way to your barn as it does your house. Give those grimy water buckets a good scrub and sweep out those mouse droppings in the feed room. This is also a great time to check out that old first aid kit hidden under musty saddle pads in the tack room. Are the supplies actually in there or has the kit been raided on occasion for an extra bandage or that jar of ichthammol? Updating your first aid kit each spring is a great habit to start. Refill supplies and check the dates on any pharmaceuticals to make sure nothing has expired. Also make sure your vet’s contact information is in there and is correct.

With a list in hand and the sunshine at your back, there’s nothing to catching up on horse health care essentials this season to ensure your summer is full of great memories.

The post Spring Horse Care Checklist appeared first on Horse Illustrated Magazine.

Read to learn how to have an effective horse deworming program.

Picture this: You’ve moved your horse to a new boarding stable. In your initial conversation with the barn manager, she tells you that all horses will be given a dose of antibiotics on the first of each month.

That sounds strange to you, but the manager says it’s just a precaution in case one horse might be sick.

If this scenario sounds perfectly ridiculous to you—and it should!—stop and consider that deworming horses every two months and rotating dewormer products is really just as irresponsible and is an unnecessary use of drugs.

Fighting Parasites

But wait. Shouldn’t you be concerned about internal parasites in your horse and do everything possible to get rid of them?

Yes. And no.

Yes, you need to have a responsible deworming program. No, you shouldn’t try to eradicate every worm in your horse. (Not that it would even be possible.)

The truth about equine parasite control is that there is no black and white, one-size-fits-all program. If you want to learn how to protect your horse now and in the future, read on to learn about the latest deworming recommendations and how to put them to use.

Getting Realistic

Here’s a basic fact: All grazing animals—including your horse—have internal parasites. The way this typically happens is that horses pick up infective larvae while grazing; those larvae migrate in the horse’s body, mature and lay eggs. These are excreted in the horse’s manure, and thus the cycle continues.

Before the advent of the first modern-era deworming drugs, many cases of colic with fatal outcomes were attributed to gastrointestinal parasites. In the 1960s, researchers discovered deworming drugs that were effective in fighting internal parasites. Many horse owners began routine use of dewormers, following the early recommendations of deworming every 60 days and rotating products.

Today, the large strongyles (“bloodworms”) that were once a common and dangerous equine intestinal parasite are now considered rare.

That’s good news, isn’t it? The fact that widespread use of dewormers over the past five decades has all but eliminated a deadly parasite is positive news. However, the downside is that other commonly found parasites have developed resistance to deworming drugs. This can occur when a dewormer is used repeatedly and frequently.

Once the parasite population contains a significant number of resistant worms, they can no longer treated with that drug class. The big concern is that we currently have only three basic chemical classes of deworming products to control internal equine parasites:

1. benzimidazoles (fenbendazole and oxibendazole)
2. tetrahydropyrimidines (pyrantel salts)
3. avermectin/milbemycins (ivermectin and moxidectin), also referred to as macrocyclic lactones

“We thought for a while that rotating products would be useful, but the data is loud and clear: it doesn’t do anything to prevent or reduce resistance,” says Martin Nielsen, DVM, Ph.D., DipEVPC, associate professor at the University of Kentucky.

Beware of Resistance

Dewormer product labels don’t mention which parasites have shown resistance to particular drugs, so you need to do your homework. Below are some common equine internal parasites that have shown resistance to the drug classes noted.

• Small strongyles: Widespread resistance to benzimidazoles and pyrantel salts has been reported
• Pinworms: Resistance to ivermectin has been reported
• Large roundworms (ascarids): Resistance to ivermectin and pyrantel salts has been reported

Common Mistakes

If resistance is a concern, then how can you protect your horse from parasites? You start by avoiding common mistakes.

“The most common mistake made by horse owners is to not use fecal egg counts, and to deworm far too often,” says Nielsen, whose focus of study is equine parasitology, including understanding the level of parasite resistance to deworming drugs.

“Some horse owners try to deworm their herds down to ‘ground zero,’” observes Craig Reinemeyer, DVM, Ph.D., a veterinary parasitologist and president of East Tennessee Clinical Research in Knoxville. “In terms of equine health, such intensity is unnecessary, and is likely to have unintended consequences.” (Reinemeyer and Nielsen are the authors of Handbook of Equine Parasite Control, published by Wiley-Blackwell.)

The unintended consequences of deworming too often and not using fecal testing are twofold:

• You may contribute to resistance
• Your horse may not be as protected as you think

“You need to know what you’re treating and if the treatment worked,” says Nielsen. “It’s as simple as that. Most adult horses do not need more than a couple of treatments a year. The risk of sticking to the old regimes is that we will just keep getting more resistance. And there are no new dewormers on the horizon, so we will eventually run out of treatment options.”

It would help to think of dewormer products with the same caution you have for other drugs, such as antibiotics, that are occasionally administered to your horse when needed. Because anyone can go to the equine supply store and buy dewormer, we tend to forget these are FDA-regulated drugs that should be used wisely and only as necessary.

How to Use Fecal Testing

In order to use dewormer drugs most effectively, you need to talk with your veterinarian and create a selective deworming program targeted to your individual horse, based on his age, exposure to parasites, climate and season.

Any responsible modern deworming program must incorporate fecal testing, which is a catch-all term for fecal egg counts (FEC) and fecal egg count reduction tests (FECRT).

Reinemeyer explains that fecal egg count testing is the only practical test currently available to demonstrate resistance to deworming drugs, and to identify which horses carry a heavy or light parasite egg count, which in turn determines how often—or not—they need treatment. (Note: Such testing applies to mature horses. Foals and young horses are more at risk for parasite infection and therefore need more frequent deworming than older horses.)

“Fecal egg counting is the way forward,” says Nielsen. “It can be performed at any time, but it makes the most sense to do it during or around the grazing season.”

Performing an egg count when you deworm and then again 10 to 14 days later will clearly reveal how effectively the deworming drug worked. If results show parasite resistance, your veterinarian can recommend a different dewormer, depending on the parasites involved.

Unfortunately, many horse owners still aren’t utilizing fecal testing in their deworming program, but for the sake of the horses, parasitologists hope this changes.

Reinemeyer explains that if you’re not using fecal testing, you have no way of knowing whether deworming treatments are actually working and what kind of parasites the horse harbors.

“This means horse owners are likely to choose an ineffective product, and then they have accomplished nothing,” he adds.

Identifying the Shedders

Fecal testing can also reveal whether your horse tends to carry a high or low egg burden. This refers to internal parasite eggs in the horse’s body that are shed in manure and into his environment.

Most horses fall into the category of “low shedders” (less than 200 eggs per gram of feces when tested). These horses typically only need deworming treatment once or twice a year.

“High shedders” (greater than 500 eggs per gram) are horses that are more susceptible to parasites and may need to be dewormed more often per year than low shedders. And about one-third of herd members might be “moderate shedders,” with egg counts between 200 to 500 eggs per gram (EPG).

Your veterinarian can review the fecal test results with you and use those results to determine what time of year deworming will be most effective for your horse, how many times treatment is needed, and which drug class of dewormer to use, depending on the parasites you’re trying to control.

How to Collect a Fecal Sample

Turn a zip-top plastic bag inside out. Place your hand inside and pick up several “apples” of very fresh manure. Turn the bag right side out, squeeze out excess air and close securely. For most accurate results, keep the sample refrigerated or on ice until your vet picks it up or you drop it off at the lab for testing.

Time for a Change

“Resistance to change is probably the single biggest obstacle to effective adult education,” says Reinemeyer.

Getting horse owners to change traditional deworming practices and follow the latest recommendations is a challenge. But it’s important that we heed the most current research. Otherwise, we will find ourselves with even more limited options to controlling internal equine parasites.

For the health of your horse, make it a point to talk with your veterinarian about updating your deworming program and, if you’re not doing it yet, to incorporate fecal testing. As a responsible horse owner, you want to follow an effective deworming protocol that provides adequate control of parasites without over-treatment that can further the development of resistance to dewormer drugs.

This article originally about horse deworming programs appeared in the April 2018 issue of Horse Illustrated magazine. Click here to subscribe!

Further reading:

Parasite Resistance and the Effects of Rotational Deworming Regimens in Horses

Internal Parasites: Strategies for Effective Parasite Control 

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Ideas about deworming practices are constantly changing as research improves. Yet even with all the education available, horse owners tend to be creatures of habit, following old routines instead of adapting to updated recommendations. However, your horse’s health can be negatively impacted if you’re relying on outdated deworming practices.

To explore and debunk some widespread deworming myths and get the most current advice, we consulted with experts from major pharmaceutical and horse care companies: Lydia Gray, DVM, MA, staff veterinarian and medical director for SmartPak; Hoyt Cheramie, DVM, DACVS, manager of large animal veterinary services for Merial Ltd; Tom Kennedy, Ph.D., consultant/veterinary pharmaceutical development for Farnam Companies; and Kenton Morgan, DVM, senior equine technical services veterinarian for Zoetis.

Follow their suggestions to make sure your horse has the best protection from parasites.

Myth No. 1: Horses should be dewormed regularly year-round.

The early deworming recommendations from the mid-1960s—treat every horse every eight weeks and rotate deworming products through the year—were based on fighting large strongyles, also known as bloodworms. These parasites were indeed horse killers and often the cause of deadly colic; however, this parasite is rarely seen today on well-managed farms. (Nowadays, small strongyles are considered a primary parasite in adult horses.)

Your deworming plan should be based on your region, individual horses, and their potential exposure to parasites—not on a calendar. There is no such thing as a “one-size-fits-all” approach to parasite protection.

“Your horse’s parasites are local, so your deworming program should be tailored to the horse’s age and possible exposure to parasites, as well as climate and time of year,” says Kennedy.

For example, in the South, hot summers greatly limit parasite transmission, while harsh winters in the North do the same. That’s why your deworming program should start with climate, then look closely at your horse’s age, environment and exposure risk.

Foals and young horses will need deworming more frequently than older horses, simply because they have not yet developed immunity and are at higher risk of parasite infection.

“If you’re in a more northern climate, you may be able to refrain from giving dewormers when parasites aren’t active (winter, your non-grazing season) and vice versa for those in southern climates,” says Gray.

If you’ve been in the habit of deworming every couple months, it may be hard to accept that your horse may not need it that often.

Myth No. 2: Deworming should totally eradicate all parasites.

The goal is parasite control, not complete eradication. You should deworm enough to keep horses healthy and to decrease the risk of recontamination.

“Horses have always had parasites,” says Cheramie. “The biggest myth is that they should have none. That’s not achievable, and by attempting to do this, we’ve created resistance and made the deworming drugs we have less effective. Instead, we want to maintain the health of horses, while simultaneously maintaining the effectiveness of the anthelmintics (deworming drugs) currently available for as long as possible.”

Myth No. 3: Targeted deworming using fecal testing is too confusing and makes extra work.

Fecal testing is the cornerstone of modern parasite control. This allows you to identify individual horses as “low shedders” or “high shedders.” Once you know this, you can deworm each horse at the appropriate frequency: low shedders less often, high shedders more often.

“Targeted deworming is actually less work, less expensive and more effective,” says Gray. “Step one is having a fecal [egg count] performed on your horse. If it comes back less than about 200 eggs per gram [EPG], then your horse is likely a low shedder and only needs deworming once or twice a year. If the results show more than 500 EPG, then your horse is likely a high shedder and needs to be dewormed more often during the grazing season in your area.” Talk to your vet for advice about which dewormers to use, how often and when.

“Checking for the presence of worm eggs is a valuable check-up for your chosen approach to parasite control,” says Kennedy. “[But] testing must be conducted and interpreted correctly.”

Horses by Peter Pearson on flickr/CC BY-SA 2.0

Myth No. 4: My horse’s fecal always comes back negative, so that means I don’t need to deworm him.

“A negative fecal egg count test does not mean a horse is parasite-free,” says Gray. A horse with a negative fecal may still have intestinal parasites; those parasites simply are not actively shedding eggs.

However, parasitologists emphasize that egg counts do give valuable information. Even when results are negative, these horses still need to be dewormed but will only require a minimum of recommended treatments.

“It’s important to keep in mind that even though a fecal egg count may not always directly correlate with the magnitude of an intestinal worm burden, it is still the best tool to determine parasite risk and to help direct our course of treatment,” says Morgan.

Myth No. 5: Rotating dewormers every two months is the best way to protect against parasites.

Several decades ago, horse owners were advised to rotate between the three chemical classes of dewormers: benzimidazoles (such as fenbendazole and oxibendazole), pyrantel, and macrocyclic lactones (ivermectin and moxidectin). Over the years, parasites have become widely resistant to benzimidazoles, somewhat resistant to pyrantel, and are showing emerging resistance to macrocyclic lactones.

“We’ve learned that rotating between chemical classes didn’t slow parasite resistance like we thought it would,” says Gray. “It’s important to make sure the dewormer you’re giving is still effective in your horse and on your farm. Your veterinarian can help with that by performing a fecal egg count reduction test (FECRT),” she continues. “Instead of counting eggs just once, a fecal egg count is done before deworming, then again 14 days after deworming, and the two numbers are compared.”

“To know which products work, there’s no other way to determine this but to use fecal testing on high shedders and working with your vet,” says Cheramie. “When you look at FECRT, you hope to see 90 to 95 percent or better reduction; anything less than that raises concerns about resistance.”

“Testing the efficacy of dewormers after use (through FECRT) defines the best drug for your horse,” says Kennedy. “If the dewormer you used is working and you used it correctly, you can keep using it.”

Efficacy testing should always be done on a group of horses; it is not an individual horse diagnosis.

Myth No. 6: For best protection, all horses on the same premises should be dewormed the same way at the same time.

The most effective parasite control program is based on a specific population of horses that share an environment. The drug class used also depends on the timing and the class of horse being treated.

For example, the rules for deworming foals are quite different than those for mature adult horses. Foals are susceptible to ascarids, and need to be dewormed at least four times during their first year.

It’s very important to develop a plan with your veterinarian because they know your farm management practices, your individual horses and their risk level. Once you have a targeted fecal testing and deworming plan in place as advised by your veterinarian, you can feel confident that you’re controlling parasites and reducing the risk of parasite-related colic and weight loss.

Myth No. 7: My horse never leaves the farm, so I really don’t need to worry about deworming.

Keep in mind that a horse can re-infect himself with his own intestinal parasites.

“Even if you have just one horse that never goes off site, he could still have quite a parasite load just from the eggs he himself passes and re-ingests,” says Gray.

It’s always a smart idea to take steps to limit the number of parasite eggs on the property, such as removing manure, managing the pasture so it doesn’t get overgrazed, not dragging manure to spread it over areas where horses are actively grazing, et cetera. Following these simple measures can greatly reduce the odds of your horse picking up parasites and continuing the cycle.

Myth No. 8: Fecal egg testing is the only thing I can do to protect my horse from parasites.

“The local environment determines whether transmission is likely to occur,” says Cheramie. “Small strongyles are transmitted almost exclusively on pastures.”

Eggs pass in the manure and develop into larvae, which crawl onto grass blades to be ingested by horses; this is how the cycle continues. Horses in the wild avoid grazing near manure, but this isn’t always possible in small or overcrowded pastures. Horses kept in stalls and dry lots full-time have lower risk of becoming re-infected.

As with so many things in life and nature, the 80/20 rule applies to parasites as well.

“Usually in a herd, 80 percent of the parasite burden is hosted by 20 percent of the horses,” says Morgan. “High shedders are responsible for the majority of parasite transmission.”

Because these horses pass more eggs in their manure, they are the ones contaminating the pasture. Keeping high shedders out of the field can significantly cut down on the number of infective larvae present.

Now that you are better armed to separate deworming fact from fiction, you can keep you horse healthier and do your part to prevent resistance to deworming chemicals in parasites.

For more, check out the Internal Parasite Control Guidelines document from the American Association of Equine Practitioners online at www.aaep.org.

CYNTHIA McFARLAND is an Ocala, Florida-based freelance writer, horse owner and avid trail rider. The author of nine books, her latest is The Horseman’s Guide to Tack and Equipment.

This article originally appeared in the March 2017 issue of Horse Illustrated magazine. Click here to subscribe!

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