Deworming Archives - Practical Horseman https://practicalhorsemanmag.com/health/deworming/ Fri, 04 Apr 2025 21:38:55 +0000 en-US hourly 1 https://wordpress.org/?v=6.8.2 https://s3.amazonaws.com/wp-s3-practicalhorsemanmag.com/wp-content/uploads/2022/02/14150009/cropped-practical-horseman-fav-icon-32x32.png Deworming Archives - Practical Horseman https://practicalhorsemanmag.com/health/deworming/ 32 32 Adopt a Smarter, Easier Deworming Plan https://practicalhorsemanmag.com/health/adopt-a-smarter-easier-deworming-plan/ Thu, 27 Mar 2025 14:56:01 +0000 https://practicalhorsemanmag.com/?p=28508 The focus of equine parasite control has changed quite dramatically since we first started using dewormers in the 1960s, especially in recent decades. The problem, however, is that veterinarians and researchers have had a challenging time getting the news out. And let’s face it—when it comes to our horses’ overall care, doing extensive research on the latest updates in parasite control isn’t usually a first priority.

Widely regarded as the world’s leading equine parasitologist, Martin K. Nielsen, DVM, PhD, DipEVPC, DACVM and former Schlaikjer Professor of Equine Infectious Disease at the University of Kentucky’s Gluck Equine Research Center, has been trying to spread the word that rotational deworming’s goal of eradicating all worms is an outdated approach to parasite control.

Rotational deworming’s goal of eradicating all worms is an outdated approach to parasite control. ©Alana Harrison

For the past four decades, the long-held practice of treating horses every eight to 12 weeks with products of different chemical classes has not prevented resistance the way veterinarians once thought it would. “This method of over-deworming caused widespread drug resistance and left veterinarians and horse owners with increasingly fewer treatment options for horses that do suffer from parasitic disease,” Nielsen explained.

To further complicate the situation, no new dewormers have been introduced since 1981 and none are in development—a process that usually takes a minimum of five years. “We are concerned that there won’t be any effective deworming medications left in the near future,” he added.

While it’s unpleasant to consider the fact that slimy, slithering worms could be taking up residence in your horse’s intestines preparing to hatch thousands of eggs that will soon contaminate your pasture, parasitic disease is even less appealing. It can wreak havoc on your horse’s intestines and put his health at serious risk.

Here, we’ll help you evaluate the effectiveness of your current deworming program to ensure your approach is successful and that you’re following new protocols recommended by researchers to keep your horse and his herdmates healthy.

New Objectives

Put in the most basic of terms, your deworming program should target the right worms with the right deworming medications at the right time of year. Unfortunately, it’s not quite as simple as it sounds because there is no single, universal parasite-control prescription that applies to all horses on all properties.

Nielsen says any modern-day deworming program—no matter the size and scale of operation—should subscribe to three primary goals:

1.) Minimize your horse’s risk of parasitic disease.

2.) Control parasite egg shedding.

3.) Maintain drug efficacy and avoid further development of drug resistance through minimal treatments; this is especially important among the medications still effective against the equine parasites posing the greatest risk.

Parasite-Control Guidelines

As experts gained more scientific knowledge about equine parasite control over the years, the American Association of Equine Practitioners (AAEP) formed a task force to provide a more modern and comprehensive set of recommendations. Nielsen explained the task force’s goal is to help veterinarians and owners determine the minimum number of deworming treatments all horses should have with certain medications. The guidelines also recommend using specific diagnostic tools to measure treatment effectiveness and to help owners determine whether horses need further treatment.

AAEP’s Internal Parasite Control Guidelines were revised in 2024. Click here to read the entire guidelines; you can also download a copy for easy reference here.

Parasite groups discussed in these guidelines include: Cyathostomins (Small Strongyles), Large strongyles, Anoplocephala perfoliata (Tapeworms), Parascaris spp. (Roundworms; Ascarids), Strongyloides westeri (Threadworms), Oxyuris equi (Pinworms), Gasterophilus spp. (Bots), Habronema and Draschia spp. (Stomach Worms), Onchocerca cervicalis (Neck Threadworm).

“The new guidelines provide veterinarians with the fundamental parameters for deworming,” Nielsen explained. “Once you understand those parameters, you can deworm according to your horse’s particular situation. Diagnostic testing results will tell you whether the treatments were effective. From there, you can make any necessary changes to ensure your plan works for your horses and property.”

Work With Your Vet

To create an effective deworming program, you need to take a number of factors into account, including:

  • What part of the country you live in
  • Your property and your horse’s living situation
  • Your horse’s age
  • His current workload

Therefore, it’s essential to work with your veterinarian to ensure you’re targeting the right worms with the right medication at the right time, because the deworming recipe will inevitably vary depending on these external factors. This is why it’s difficult to recommend particular deworming products, classes of medication or a timeline for when owners should deworm with specific medications.

“Your veterinarian will know what species are the biggest threat based on your geography, pasture density, your horse’s age and the amount of traffic on your property,” Nielsen noted. “So, he or she can advise you on the right products and when to use them.”

Fecal Egg Counts Are Crucial

To find the ideal balance between administering too much and too little deworming medication, monitor treatments through fecal egg testing. “The goal is to deworm only as often as necessary for your particular horse,” Nielsen said. “Deworming too much, as we’ve done for decades, leads to drug resistance. But deworming too little won’t reduce worm burdens.”

A veterinarian examines a manure sample under a microscope to measure if the horse is a low, moderate or high shedder. ©Dusty Perin

The best way to determine what’s appropriate for your horse is to first measure the levels of parasite eggs—primarily small strongyles, which are the most common—existing in his digestive system, or “shedding” in his manure, using a fecal egg count. Then repeat the test two weeks after treatment to evaluate how well it worked.

Your veterinarian will perform a fecal egg count from a sample of your horse’s manure under a microscope. Several methods are used, but the results—expressed as eggs per gram—measure the type of strongyle shedder a horse is:

  • Low: less than 200 EPG
  • Moderate: 200 to 500 EPG
  • High: more than 500 EPG

“The overwhelming majority of mature horses are in the low-shedding category,” Nielsen said, and he offers statistics from his research: “Typically, 50 to 70 percent of the horses in a herd will be in the low-shedding category. The moderate shedders will always be a small proportion of the herd, usually about 10 to 20 percent. The remaining horses are the high shedders—often around 10 to 20 percent.”

What accounts for the differences? “We see this in adult horses and only for the strongyle parasite category. Horses seem to find their general level of egg shedding, which they maintain throughout their lives, and a majority of horses will have very low or negative egg counts,” Nielsen said. “We believe immune status has a lot to do with strongyle shedding status. Horses who move a lot, are training hard or trailered to shows every weekend tend to have higher egg counts. Horses that are hospitalized for non-intestinal conditions like lameness or reproduction can also have increased egg counts.”

What does this mean for how often a horse should be dewormed? Shedding status correlates with frequency and timing. “For low shedders, two annual dewormings—one in the spring and one in the fall, depending on the length of the grazing season—is likely all that’s needed,” Nielsen explained. “Some horses might need even fewer treatments, while high shedders might require more, especially in climates where the grazing season extends beyond five or six months.”

Many internal parasites begin life as eggs in manure piles. ©Alana Harrison

Follow-up testing: Unfortunately, a majority of horse owners who do fecal egg count tests, tend to only do so when they suspect parasites are threatening their horses’ health and rarely follow AAEP’s recommendation to repeat the fecal egg test after treatment. “You can’t just look at a horse a say, ‘Well, he’s got that spark back in his eye so it must be working,’” Nielsen explained. “A lot of people are using products that don’t work. But they will never know if they don’t check. You have to do a second fecal egg count to verify the medication is effectively controlling the parasites you’re targeting, and you have to routinely perform fecal egg counts to continue monitoring a dewormers’ efficacy.”

Nielsen also advises horse owners not to rely solely on the information provided on a drug’s label to rate a dewormer’s effectiveness. “It’s historic information—in other words, how the product worked when it was first introduced. But often, it does not represent the current situation as resistance is ignored,” he noted. “So, the only way to know, is to test.”

Unfortunately, research shows that fecal egg counts are not yet widely used by horse owners. “We are seeing owners deworm less now compared to 20 years ago, but they aren’t really using egg counts more and they almost never test for treatment efficacy,” Nielsen said. “In the end, the explanation is simple: Reducing the number of treatments does not cost anything; you actually save money. But collecting fecal samples and running egg counts comes with a cost. So, we researchers still have a lot of work to do to get the word out.”

Know Thy Enemies

Nielsen says it’s entirely normal for horses to have parasites. “For the most part, these worms—regardless of species—don’t do anything harmful. Horses can harbor substantial parasite burdens without being affected,” he explained. “Equine disease caused by parasites is the exception to the norm. In these rare instances, there are almost always other contributing factors that render a horse more susceptible to disease from parasites.”

Over the past several decades, certain equine parasite populations have shifted, meaning parasites that once posed the greatest risk to horse health aren’t such a threat anymore, and others that we previously believed weren’t a problem now pose a risk. In adult horses, the primary parasites of concern are small strongyles and tapeworms. In foals and weanlings, ascarids remain the most important parasite to target.

Ascarids

When newborn foals first sniff around the pasture, they ingest ascarid eggs, acquire this worm infection and then naturally eliminate the resulting parasite infection within a year. Nielsen says all foals experience a phase of ascarid infection but after eliminating the worms, horses usually never get this parasite again.

Signs if disease: Rarely, ascarids can cause disease, discomfort or malnutrition and stunted growth in foals. Migrating larvae can also cause airway inflammation, and in the most severe cases, ascarid infestations can clog and even impact the small intestinal tract. Small-intestinal impactions are difficult to manage, very painful for the foal and typically requires hospitalization, veterinary supervision, pain medication and sometimes surgery.

Small strongyles

As foals transition to yearlings, your deworming plan shifts its emphasis from ascarids to small strongyles and tapeworms. Once believed to be nothing more than a nuisance, small strongyles (also called cyathostomes) are now regarded as the primary intestinal parasite threatening the health of adult horses. Ubiquitous among horses on pasture, these worms reside in a horse’s large intestine.

Signs of disease: Small strongyle infestations can cause mild weight loss, a coarse or dull hair coat, exercise intolerance, decreased performance and in rare cases these parasites can cause a life-threatening condition that results in severe diarrhea, weight loss and edema. Unlike large strongyles, the small strongyles’ larvae don’t migrate as extensively and damage intestinal blood supplies, which actually makes them a much more subtle and sneaky parasite.

“As part of their life cycle, the small strongyle larvae burrow into the wall of a horse’s large intestine where they go into a hibernation-like state for long periods of time until they all of a sudden wake up and emerge,” Nielsen explained. “When a horse has a high accumulation of these encysted larvae all coming out of hibernation at the same time, it creates a vast inflammatory condition in the large intestine that causes diarrhea.”

Tapeworms

For many years, these parasites weren’t known to cause a lot of disease in horses, but tapeworms have emerged as a growing concern—especially in certain parts of the country. Horses can only ingest tapeworm larvae through an intermediary host—most commonly, a nearly invisible mite that resides in grass and is more prevalent in lush grass and moist areas. There are pockets of equine tapeworm infestations throughout the U.S. because the life cycle of this worm is different from that of other parasites.

Signs of disease: Once ingested, Nielsen says tapeworms tend to hoover around the junction between the small and large intestine and eventually attach to the large intestinal wall near this junction. Large infestations in this area can result in physical obstruction and severe colic requiring surgery.

It can be difficult to measure treatment efficacy for tapeworms because its larvae aren’t always identified in traditional fecal egg counts. While there are specialized tests that can identify tapeworm eggs, many veterinarians advise owners to treat for tapeworms once or twice a year, regardless of verified egg counts. Since these parasites tend to be regional, it’s always important to work closely with your veterinarian to determine if this is the right course for your horse.

The Lesser Culprits

In addition to the primary parasites of concern, there are a handful of less-prevalent worms that occasionally cause problems or disease in horses.

Large strongyles: While these worms were once considered the most threatening equine parasitic pathogen, there has been a significant reduction in large strongyle population and disease over the last 40 years—thanks to a lack of drug resistance. If your horse does get this type of roundworm, however, it can wreak havoc on his digestive system. The adult worms take up residence and remain in the large intestine, but the larvae migrate through blood vessels that supply the intestines.

Pinworms: These parasites rarely lead to severe disease in horses, but they do cause acute itching and tail rubbing. Pinworm eggs can be identified using a “Scotch Tape test,” in which a veterinarian takes an impression of the horse’s skin near the rectum and then examines the tape under a microscope.

Pinworms do little harm in the intestinal tract but can cause intense itching and tail rubbing when female worms deposit yellow eggs and a sticky, irritating substance around the horse’s anus. ©Paula da Silva/arnd.nl

Summer Sores: More prevalent in dry parts of the country, this fly-borne parasite normally establishes itself in the stomach after a horse ingests a dead fly carrying the larvae. Occasionally, however, flies deposit the larvae into an open wound, causing slow-to-heal skin sores or ulcers that can become chronic. While this is eventually a dead end for the parasite, it can still cause significant and chronic irritation for the horse.

Neck threadworm: As its name suggests, this parasite—typically, a single adult female—resides in the large ligament of a horse’s neck. Without an abundant blood supply, this is an ideal place for the threadworm to hide from a horse’s immune system. The adult worm is not known to cause horses any discomfort, whereas the tiny microfilaria can spread and cause skin inflammation. “It’s kind of like the Alien movies where the Mother Alien is hiding somewhere hatching her baby aliens,” Nielsen said. “That’s how this parasite operates.” The threadworm’s microfilaria can be treated, but there are no effective treatments against the adult worm.

Bots: Botflies lay eggs on a horse’s hair; when the larvae hatch, they migrate toward the mouth to enter the digestive tract or the horse ingests the larvae when he licks or bites his coat. The larvae then attach to the horse’s stomach wall or the first few inches of the small intestine. Botflies are relatively benign but in large numbers they can cause damage to the stomach lining or block passage of food from the stomach to the small intestine.

Deworming Arsenal

The AAEP guidelines list four chemical formulations commonly used to treat internal parasites in horses though incidence of resistance is increasing.

Benzimidazoles: These have been a mainstay of equine parasite control for more than 50 years and act by interfering with parasites’ metabolism. Agents in this class include:
• fenbendazole
• oxfendazole
• oxibendazole.

All three are effective against ascarids, large strongyles and pinworms, but small strongyles are widely resistant. Oxibendazole also works against threadworms.

Tetrahydropyrimidines cause paralysis in parasites. Small strongyles are commonly resistant to the agents in this class:
• pyrantel pamoate, which works against ascarids, large strongyles, pinworms and tapeworms
• pyrantel tartrate, which is formulated in alfalfa pellets as a feed-through dewormer. It is effective against ascarids and large strongyles, but only as a preventive. It will not purge parasites from the intestines.

Macrocyclic lactones block nerve transmissions to paralyze worms. Agents in this class include:
• ivermectin
• moxidectin.

Both work against most of the common equine parasites, but ascarids are widely resistant. In addition, ivermectin does not kill encysted small strongyles.

Isoquinoline-pyrozines is a class that contains one agent:
• praziquantel, which is effective only against tapeworms.

Additional Management Tips

Dewormers are just one facet of an effective parasite control plan. There are several strategies, including good pasture management, that can also reduce a horse’s risk of exposure and possible infection that researchers recommend:

Provide sufficient space: The ratio of animals you keep on a particular pasture in relation to the pasture’s health and size—is one of the most simple yet effective parasite-control strategies. “If you stock too many animals on a pasture given its size, it will quickly become overgrazed, leaving horses more exposed to parasites,” Nielsen explained. “When horses eat down every last blade of grass, they end up ingesting a lot of parasites.”

Good pasture management is crucial for your overall parasite-control plan. ©Alana Harrison

Horses tend to establish separate eating areas (“lawns”) and waste areas (“roughs”) in their pastures. As a general rule, provide about two acres of pasture space per horse to help prevent overgrazing and reduce the chances that parasite eggs and larvae in the roughs will be consumed.

Remove manure: Pick up and remove manure on a regular basis—at least once a week.

Mow and harrow pastures: Do this periodically to break up manure piles and expose parasite larvae to the elements. Frequency will depend on the weather and the length of time the pasture can be rested afterward. Larvae can survive freezing temperatures, but they can only tolerate heat and arid conditions for a few weeks.

Age matters: Be sure to consider the ages of all the horses on your property and treat youngsters as high shedders.

Test new herdmates: Evaluate the health—including shedding status—of new horses before turning them out with a herd.

Pasture rotation: Rotate pastures when possible or section off portions to give parasites time to die off while the horses graze elsewhere. This can take three to four weeks in hot, dry weather—when the temperature is above 85 degrees Fahrenheit—and as long as six to nine months during colder times of the year.

Mixed-animal grazing: Use mixed or alternate grazing with other animals like cattle and sheep—species that aren’t susceptible to exactly the same parasites as horses and vice versa. “Mixed grazing leads to better pasture utilization, as the cattle will eat the rough areas horses typically don’t eat,” Nielsen explained. “The cattle not only ingest a high volume of equine parasites, they also help eliminate many of the protections parasites seek on pasture, including moisture in vegetation and shade created by high grass. More exposure to direct sunlight will create drier pasture conditions and a lower parasite infectivity.”

Future of Deworming

Time will tell how horse owners and veterinarians put the scientific community’s latest recommendations on equine parasite control to use. As Nielsen sees it, one of the greatest challenges for researchers is simply getting their message out. “We have to communicate as effectively as possible and make good use of the platforms available,” he said. “Scientists in general have to become much better at using social media.”

Nielsen also points to ongoing research and product development that will shape the future of equine parasite control. Among the advances in use and on the horizon:

Parasight System: A smartphone-based fecal egg diagnostic and intestinal parasite management tool developed by Nielsen and colleagues that allows veterinarians to perform rapid, reliable, quantitative, on-site and in-house fecal egg counts in five minutes.

Ultrasound exam: This method helps detect heavy ascarid burdens in foals and identify the risk of impactions.

Deworming agent: This utilizes a protein produced by the soil bacterium Bacillus thuringiensis to kill parasites. Nielsen says the research has moved beyond the lab and holds promise.

Computer simulation model: These models have the potential to offer insights on the timing of deworming treatments by using weather data—primarily temperature and precipitation rates—to identify the grass-growing/parasite-transmission season in virtually any locale.

Deworming Takeaway

Martin K. Nielsen, DVM, PhD, DipEVPC, DACVM and former Schlaikjer Professor of Equine Infectious Disease at the University of Kentucky’s Gluck Equine Research Center, has been a longtime leader in equine parasite control. Courtesy Martin Nielsen

These efforts and more will influence how internal parasites are dealt with in horses in the months and years to come. For now, a strategy that identifies and treats according to a horse’s individual needs is likely to yield the most desirable results.  

For more tips on smart pasture management, click here.

Learn how to administer paste dewormer the right way—and without making a mess—here.

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To Do This Month: March 2025 https://practicalhorsemanmag.com/lifestyle/to-do-this-month-march-2025/ Sat, 01 Mar 2025 21:42:40 +0000 https://practicalhorsemanmag.com/?p=28120 As the last winter snow thaws and the days start getting longer, check out our March To-Do List for upcoming events, new training tips on E+ and everything you need to get a jump start on spring to keep your horse healthy, happy and performing his best.

EVENTS

EQUESTRIAN+ will be livestreaming the Galway Downs International Horse Trials in Temecula, California, on March 27 – 30. Courtesy Robert Kellerhouse/Galway Downs

Watch & Learn on E+

Livestream: We’re super excited to announce that we’ll be livestreaming our first Galway Downs International Horse Trials in Temecula, California, on March 27 – 30. Watch on EQUESTRIAN+.

Gymnastics for Form: In this new video series on E+, Olympic show jumper Margie Engle explains how to teach your horse to develop form over fences and demonstrates flatwork and gymnastic exercises, including raised cavalletti, bounces and an in-and-out combination with a vertical and oxer. Check out her new series here.

Check out Anna Buffini’s new video series on EQUESTRIAN+. ©Amy K. Dragoo

Lateral Work, Changes & Trot Lengthenings: Dressage phenom Anna Buffini demonstrates how lateral movements build upon one another throughout a horse’s development and how to develop flying changes and trot lengthenings through the levels. Check out her new video series on EQUESTRIAN+ here.

Spring Health Checks

Schedule a dental exam and have your horse’s teeth floated if necessary. ©Alana Harrison
  • Carefully check your horse’s pasterns for scratches.
  • Inspect his hooves for thrush and/or soggy, weak hoof walls. For more on how to treat and manage thrush, click here.
  • Get a Coggins test if your horse will be traveling this spring and summer.
  • Do a fecal egg count test and deworm based on your horse’s living situation and your veterinarian’s recommendations.
  • If your horse has had little to no access to quality pasture over the winter, consider checking with your vet to determine if you should have her vitamin E serum values checked.
  • Schedule a dental exam and have your horse’s teeth floated if necessary.
  • Work with your veterinarian to determine if your horse is due for any springtime vaccinations.
  • As your horse is exposed to more light with the longer days and his winter coat starts shedding out, accelerate the process by using a shedding blade over the large areas of his body. Follow up with a stiff body brush to remove loose hair, dirt and dead skin cells to allow his sleeker, summer coat to grow in.
  • Schedule a farrier appointment ahead of show season.
  • Have your horse’s blood selenium levels check if you live in a selenium-deficient area.
  • If your mare tends to get less-than-desirable to ride when she’s in heat and you use supplements, herbs or hormones to help manage her unwanted behaviors, check with your vet to see if now is the right time to start.

Barn & Trailer Management

To avoid wrestling mud this spring, take measures to control the sludge before the last snow thaws. ©Alana Harrison
  • Check fence lines: Winter weather can be hard on fences. Examine your fences and enclosures carefully and make any necessary repairs.
  • Clean out water troughs: Especially if your troughs have been partially frozen throughout the winter, give them a thorough cleaning.
  • Trailer tune-up: This is good to do any time of year, but especially if your trailer has been sitting around for a few months, be sure to check the hitch, wheel bearings, tire pressure, lights, brakes, flooring and all latches.
  • Start fly control: If you use a fly-control system like Fly Predators®, it might be time to deploy them depending on what part of the country you live in.
  • Mud management: Use footing material like gravel or wood chips in areas heavily trafficked, manage manure, install gutters and downspouts, intercept surface flows and plant trees and shrubs to prevent your barn and surrounding areas from becoming a muddy mess as the last winter snow thaws.
  • Spring cleaning: Power-wash stalls, scrub feed buckets, clear cobwebs, unclog gutters, declutter your medicine cabinet, organize your tack trunk, freshen up community areas and plant flowers to add a pop of color to your barn this spring.

Training & Show Prep

  • Get the fresh out: Especially if your horse has been cooped up for much of the winter, help him get excessive energy out and ramp up his fitness with longeing sessions.
  • Ready, set, check: Start your horse-show checklist to get all of your tack, apparel, equipment and other gear organized and ready for the competition season. Throw old or empty supplies out (or recycle) and replace as needed.
  • Last call: Ensure all elements of your show apparel are clean, in good repair and working properly (if you wear a safety vest, for example). The same applies to your horse’s tack and other gear.

Baby On the Way?

If your mare’s due date is on the near horizon, start preparing a foaling stall and kit now to ensure you’re prepared when the big day comes. ©Amy K. Dragoo
  • Prepare a foaling stall: Ideally, set up your mom-to-be’s foaling stall in a quiet location away from other horses and barn traffic. It should be roomy and open and free of any objects or protrusions that could pose a safety risk; be sure to provide safe water sources, non-stick bedding, fresh air and climate control for heat or cold. Washable walls and flooring will also make your life easier. Move your mare there well before her due date so she can get accustomed to her new quarters. For our full pre-foaling checklist, click here.
  • Assemble a foaling kit: Key items include a halter and lead for your mare, headlamp with fresh batteries, stopwatch, notepad and pen (or your phone) to keep track of noteworthy events, tail wrap for your mare, small hand towels, large towels for drying the foal, bulb syringe, trash bags and disinfectant. Also, make sure you have your vet’s number programmed into your phone.
  • Set up a foaling web cam: As your mare’s due date approaches, install a foaling webcam so you can easily keep an eye on her from anywhere and ensure it’s working properly well before the big day gets close.

Happy March, from your friends at Practical Horseman!

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New DIY Tapeworm Test https://practicalhorsemanmag.com/health/new-diy-tapeworm-test/ Wed, 05 Jul 2017 17:53:11 +0000 http://ci020efe31500026f4

Resistance to deworming medication is a growing concern in the horse world, making it ever more important to deworm only when testing shows your horse actually has a worm burden. That’s especially critical when it comes to tapeworms since there are currently only two effective drugs to fight them—and the parasite is a common cause of serious colic, explains Corrine Austin, PhD, of Austin Davis Biologics in the U.K.

Researchers have developed a new tapeworm diagnostic test, called EquiSal, that allows owners to collect a horse’s saliva for analysis in order to determine if parasites are present. Courtesy, Dr. Corrine Austin

Unfortunately, traditional fecal egg counts don’t work well to determine tapeworm load. A blood test—technically known as a serologic ELISA test—is the preferred diagnostic tool. But the blood samples needed must be collected by a veterinarian.

Dr. Austin and her colleagues wanted to find a similarly effective diagnostic aid that would allow horse owners to collect samples themselves. They developed a test, called EquiSal, that uses a horse’s saliva. To evaluate the test’s reliability, the team took blood and saliva samples from more than 100 recently deceased horses and tested them using the standard serologic ELISA test and the EquiSal test, respectively. They also visually examined the horses’ intestines and counted any tapeworms found.

“The results from the saliva test correlated [or related] well with the blood-test results as well as the actual number of tapeworms present,” says Dr. Austin. “It’s important for a diagnostic test to correlate well with the gold standard of infection—in this case, tapeworm numbers present at post mortem.”

EquiSal test kits are currently in use in the U.K., and Dr. Austin hopes they’ll be available in the U.S. this spring. The kits contain a specially designed saliva collection swab that the horse owner places onto the horse’s tongue, explains Dr. Austin. An indicator turns pink when enough saliva has been collected. The owner puts the swab in a provided tube and mails it to a central collection point; from there it’s sent to the U.K. for testing. About one to two weeks later, the horse owner receives results showing whether the horse has a low, borderline or moderate/high tapeworm burden. Deworming is recommended for all but the low-burden horses.

With 250,000 U.K. samples tested, only 25 percent have identified horses as having a tapeworm burden requiring treatment. This means that in a standard rotational deworming plan a large percentage of horses may be unnecessarily medicated. By preventing that, Dr. Austin and her team believe their test can
be a key component in reducing parasite resistance.

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Crowdfunding Equine Research https://practicalhorsemanmag.com/health/crowdfunding-equine-research-16088/ Wed, 02 Apr 2014 10:43:05 +0000 http://ci02027868c0002576

The war on worms has entered a new stage as more equine parasites develop resistance to common deworming medications. It’s a 21st-century problem, and one scientist is taking a 21st-century approach in the hunt for alternative treatments.

Using money raised by crowdfunding, Dr. Martin Nielsen plans to collect parasites from horses in a research herd for a study testing a new treatment to fight worms. | Courtesy, Martin Nielsen, DVM

Martin Nielsen, DVM, PhD, DipEVPC, an equine parasitologist and assistant professor at the University of Kentucky Gluck Equine Research Center, has turned to online crowdfunding to raise money for tests of a promising new control method. It’s the first such crowdfunding project at UK and possibly, the school says, in the field of veterinary science.

Dr. Nielsen launched his crowdfunding campaign, called “Let the germs get the worms: Testing a novel probiotic compound for treatment of equine parasites,” at the website http://equineparasitology.ca.uky.edu/. As with other crowdfunding efforts, the idea is to reach out to the general public and draw small donations from many people. Visitors to the site can sign up for more information on the project, access videos and educational information and enter a forum to ask Dr. Nielsen questions about parasite control. “They can sign up without donating,” Dr. Nielsen says. “Also, they can donate without signing up.”

The compound Dr. Nielsen is investigating is a crystal protein produced by Bacillus thuringiensis bacteria, which are widely found in nature. The bacteria are used in natural pest controls, including the “dunks” floated in ponds to kill mosquito larvae without harming fish. Scientists at the University of California have found that certain crystal proteins produced by these bacteria can kill intestinal worms without harming mammals, and researchers there and elsewhere are investigating their use in laboratory and other animals.

Dr. Nielsen plans to explore the effect of the bacterial protein against important horse parasites. The crowdfunding project set a goal of raising $30,000 by March 10 to help finance the first step: collecting parasites from horses in a research herd and testing in the laboratory. “We will test for the presence of receptors for the bacterial protein and test the effect against different horse parasites under laboratory conditions,” Dr. Nielsen says. He hopes to use the results to apply for a larger grant for testing the protein in horses.

Initial response to the crowdfunding project was strong, Dr. Nielsen reports. “Lots of great questions have been posted on the site,“ he adds, and interaction with visitors is valuable. “A good question can inspire us to set up the next research project.”

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Deworm Your Horse the Right Way https://practicalhorsemanmag.com/health/deworm-your-horse-the-right-way-11774/ Wed, 20 Feb 2013 17:21:04 +0000 http://ci0202786c5006272a Parasite control is a critical component of your horse’s overall health-care plan. You probably have a system for what type of deworming products to give your horse and when, but it won’t be effective if you can’t get the correct dosage into him. With all but the most saintly of horses, administering paste dewormers without getting yourself and the stall splattered with paper-much-like goo takes a little strategizing.

In this article, I’ll give a step-by-step plan for minimizing the mess and ensuring that your horse gets his full dose. Dr. Mary Griffin, DVM, a colleague in ambulatory practice with a specialty in ultrasonography in Chester County, Pennsylvania, is ?demonstrating the techniques I use.

How Much Is Enough?
1. Deworming medications are not effective when given in an inadequate dose, so always err on the side of giving more rather than less of the recommendation for your horse’s weight. One easy way to estimate your horse’s weight is with a weight tape, available through feed and tack stores. Also be aware that the average syringe contains enough medicine for a 1,200-pound horse, which is less than many of today’s warmbloods weigh. So, if your horse is on the larger side, part of an additional syringe may be in order. Consult your veterinarian, who may suggest that, because deworming medications are very safe, even at higher-than-recommended doses, you should administer the dose for an additional 250 pounds (usually one mark on the syringe) more than you think your horse weighs.

When it comes to foals, smaller ponies or miniature horses, overdosing can become a problem, so you should always consult your vet before determining the appropriate dose, and be sure during the actual administering that an overdose does not occur.

2. It’s also a good idea to have a little extra medication on hand, in case more ends up on the outsides of your horse’s lips or on the ground than you expected. These drugs are not effective when given in small amounts over a period of time. The whole dose must be administered in one sitting. So if he doesn’t swallow his full share within one day, wait a few days and start over with a new plan and another full dose.

Say Ahhhh!’
3. It’s much easier for your horse to spit out the paste when he can combine it with a wad of food. So before administering the medication, check to be sure that he has no hay, grass or grain in his mouth. Holding the side of his halter with one hand, gently pull his lips back on the opposite side with a finger (being careful to keep it clear of his teeth) to check for food. Repeat on the other side of his mouth.

4. If you feel comfortable, encourage him to open his mouth by pressing a finger in the gap between his incisors and molar teeth, where the bit goes. On the opposite side and with your other hand, reach through the gap in the teeth to grasp his tongue. Gently pull it to the side and look into his mouth for food. Never apply excessive tension to the tongue, as it can result in permanent damage to the tongue’s nerves. If your horse resents your pulling on his tongue, LET GO!

If you spot any food, this manipulation probably will compel him to finish chewing and swallowing it or spit it out in the next moment or two. Make sure there’s no food available for him to grab. If he doesn’t appear to be swallowing the food, carefully try to grasp the hay and remove it, steering clear of his teeth.

At this point, you should have a good idea of how your horse feels about having things put into his mouth. Most horses are fairly comfortable with the idea and, consequently, relatively easy to deworm. However, the occasional horse will take great exception to this process. Some hate it so much they’re downright dangerous. Life’s too short to risk your life for this simple purpose. If your horse throws his head violently or refuses to stand quietly, consider mixing his dose with food instead (see “Mix It Up” at left).

Down the Hatch
Where exactly you inject the medication depends on your horse. Some swallow it wherever you squirt it. Some do better if you put it on their tongues; others do better if you squirt it back between the cheek and molars. A few are so adept they spit it out regardless of where you put it. (For those types, consider mixing the dose with food.)

It may take some experimentation to find out which place works best for your horse. In any case, when you put the syringe in his mouth, be careful not to poke his lips or bump his teeth or gums, which can make the experience less pleasant for him?and harder to tackle the next time you deworm. Below are two techniques for administering the paste.

5. Begin by holding his halter with one hand and sliding the tip of the syringe gently into the corner of his lips, between his molars and incisors. Inject the paste directly onto the tongue, squeezing a small amount out at a time (leaving the syringe in his mouth as you pause), allowing your horse to swallow between or

6. slide the syringe back between the molars and cheek and squirt it toward the back corner of his mouth. Again, squeeze out only a small amount at a time. If you use this method, be especially careful to avoid bumping his teeth, which can be very annoying to most horses.

After completing her large-animal surgery residency and serving as a staff surgeon at the University of Pennsylvania’s New Bolton Center in 1980, Midge Leitch, VMD, DACVS (Diplomate, American College of Veterinary Surgeons) opened a referral practice in which she developed a specialty in performance-limiting problems in racehorses and sporthorses. In the following decades, she traveled extensively with the US Equestrian Team, including trips to three Olympics and multiple World Championships. She returned to New Bolton Center in 2005 as a radiology clinician, assuming responsibility for equine diagnostic imaging, including digital radiography, MRI and CT.

Reprinted from the August 2011 issue of Practical Horseman magazine.

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An Equine Deworming Strategy to Prevent Parasite Resistance to Medications https://practicalhorsemanmag.com/health/an-equine-deworming-strategy-to-prevent-parasite-resistance-to-medications-11583/ Fri, 15 Jul 2011 17:28:05 +0000 http://ci020278698006272a Worms that can fight off the effects of the chemicals you rely on to protect your horse? Superworms? It sounds like a nightmare. But it’s becoming a reality: Already some dangerous equine parasites have found ways to resist widely used deworming medications, and the problem is spreading.

Luckily, people are smarter than worms. Here’s how one farm beat resistant worms and how you can ?apply the same strategy to protect your horse from this threat.

Superworms?
Several years ago, Dr. Dianne Little and other researchers from the North Carolina State University College of Veterinary Medicine began following horses on a breeding farm in central North Carolina. For years the farm had dewormed horses every eight weeks, switching drugs each time from fenbendazole to pyrantel to ivermectin. Yet high levels of worm eggs?specifically, small strongyle (cyathostome) eggs?were turning up in manure just a few weeks after treatment. In addition, some weanlings were showing signs of a disease condition called larval cyathostomiasis, which develops when small strongyle larvae become encysted in the gut wall.

Further checks showed that the worms were resistant to two of the three broad classes of deworming medications: benzimidazoles (such as fenbendazole) and pyrantel salts (pyrantel pamoate or pyrantel tartrate). Resistance develops when a few worms survive treatment and pass the traits that helped them survive to their offspring. On this farm, only the third class of dewormers?macrocyclic ?lactones (ivermectin and moxidectin)?worked against small strongyles, currently the most widespread and dangerous equine internal parasite.

The NCSU veterinarians wondered if they were watching that last bastion fall. Ivermectin was still killing worms on this farm, but the interval it took for eggs to ?return to high levels after treatment was shrinking?from eight weeks to three or four weeks and even two weeks in some horses. Shorter egg reappearance time is thought to be an early sign that resistance is developing. Were the worms on this farm turning into ?superworms, unscathed by all available ?medications?

To get a handle on the problem, veterinarians mapped out a two-part plan. First, the farm switched from rotational deworming to a strategic program, treating each horse only when its fecal count rose above target levels (200 eggs per gram for mares and 100 epg for foals). Horses aren’t equally susceptible to parasites and produce variable amounts of eggs in their manure. On a typical farm, 20 percent of the horses shed 80 percent of the worm eggs. The idea was to identify the high shedders, treat them effectively and manage the others with fewer treatments. Reducing treatments would save money and might help reduce the chance that worms would develop resistance.

Second, the veterinarians recommended changes in pasture management. Strongyle eggs are passed in manure. Larvae hatch in the field and are picked up by grazing horses. Reducing the number of horses grazing each pasture, rotating and resting pastures to interrupt worm life cycles and stopping the practice of spreading uncomposted manure on fields could reduce reinfection.

These steps weren’t taken right away, and problems continued. But about a year after new managers took over and made the changes, egg reappearance times began to increase. Ivermectin, it turned out, still worked against the worms. The problem had been rapid reinfection from pasture that was heavily populated with worms due to poor management.

Winning Strategy
Veterinarians 1, worms 0?but this farm’s experience with resistant worms was far from unique, Dr. Little notes. In some areas, 90 percent of farms have benzimidazole-resistant stron?gyles; 20 to 40 percent have pyrantel-resistant worms. Indiscriminate dosing, she and other researchers say, encourages resistance to develop. That concern applies to daily as well as interval deworming medication.

Low daily doses of pyrantel tartrate, for example, kill strongyle larvae soon after they enter the horse. But what if some survive the frequent exposure to a low dose? There may then be selection for worms resistant to higher doses of drugs in the pyrantel class. Dr. Little found evidence of this at a boarding stable where daily pyrantel tartrate was no longer controlling strongyles; resistance to pyrantel pamoate was also identified.

Many researchers believe it’s just a matter of time until worms develop ?resistance to all three classes of dewormers. “No new drug classes are in the pipeline, so veterinarians and horse owners need to work together to extend the life of the drugs we have,” Dr. Little says. For that, think strategically.

Parasites are a herd problem, Dr. Little says, so a good plan covers all the horses on the property, whether that’s your backyard or a large boarding stable. The number and age of the horses, the amount of pasture they have and your geographic location are all factors. Frequent trips to shows and new horses coming onto the property can increase ?exposure risks.

Your veterinarian can help you devise an appropriate strategy. The first step is to do fecal egg counts?ideally, on all horses on the property, on the same day, so you can identify the horses that shed large numbers of eggs. (The box “Egg-Count Basics” below explains how.)

If your farm is typical, some horses will have higher counts than others. They’re most likely the high shedders; further tests can confirm that. These horses contribute more to the herd problem, and they may be at risk for larval cyathostomiasis, especially if they’re young or very old. You should also alert your veterinarian to any horse that has recurrent colic, diarrhea, poor body condition or a rough coat. These signs can appear in horses with high levels of encysted small strongyles, even if fecal egg counts are low. So these horses may need additional monitoring and treatment. (For tips on how to manage your horse’s deworming program in a boarding situation where the whole barn is not using the program, see box “What If You Board?” at the end.)

Once you’ve assessed the problem, reach for your weapons: medication and management.

Strategic Medication
Use medication to eliminate worms without overtreating your horses. Here’s how:

Get the dose right. It’s based on weight. Use a weight tape to get an estimate. Be sure your horse swallows all the medication.

Check effects. A fecal egg count 10 to 14 days after deworming will tell you if your medication is working. The count should drop by 95 percent. If it doesn’t (or if you have a high initial egg count in the face of daily deworming), something’s not right. Your horse may not have ?received a full dose, or you may be dealing with resistant worms.

Test and re-treat. Repeat fecal counts in six to eight weeks (or at the time you might expect to deworm again, depending on the product you used), and treat only horses with egg counts above 200. Initially, you may need to run farm-wide fecal counts every couple of months. Once you’ve identified the high shedders, less susceptible horses may need to be checked and dewormed only a couple of times a year.

Cover all bases. Egg counts mainly tell you about small strongyles?the major threat but not the only one. Even if your horse’s count never rises above 200, you need to consider:

  • Tapeworms: They’re hard to ?detect. If they’re a problem in your area, treat every six or 12 months with praziquantel (sold in paste combos with ivermectin or moxidectin) or a double dose of a pyrantel pamoate paste.
  • Large strongyles: Once a leading cause of devastating colic, they’ve been largely wiped out by modern dewormers. But on a program with less frequent, targeted treatments, there’s a chance they could return. Treatment every six to 12 months with ivermectin will keep them at bay.
  • Ascarids: These worms, which can be picked up year-round, mainly affect young horses. Deworming every six to eight weeks from ages 8 weeks to 2 years will keep numbers from building up. All three classes of drugs work, although there have been reports of ascarids resistant to ivermectin.

These steps should also protect your horse against many other internal parasites (such as pinworms), so you won’t need to do anything special for them. For example, a fall treatment with praziquantel and ivermectin or moxidectin will control tapeworms, pinworms, bots and strongyles in one dose.

Strategic Management

  • Use management to cut the risk that worms will reinfect your horse. Different parasites have different life ?cycles, but most spread their eggs or larvae through manure. How you handle the poop, then, makes a big difference.
  • Pick up manure in paddocks at least twice a week.
  • Put hay and grain in feeders, not on the ground. Don’t allow manure to contaminate water troughs.
  • Don’t overstock pastures. Good stocking rates vary, but two acres per horse is a good rule of thumb. When horses have plenty of space, they tend to graze away from ?manure piles.
  • Harrow pastures in hot, dry weather to break up manure piles and expose eggs and larvae to the ?elements. Strongyle larvae can’t ?toler?ate heat and drying for long, ?though they can withstand freezing.
  • Don’t spread manure on fields where horses graze. Compost it. The heat in a good compost pile will kill worm eggs.
  • Rotate pastures by resting fields for three to four months or allowing other animals?sheep or cattle, say?to graze. This interrupts parasite life cycles. Small strongyle larvae may hatch, but if they find no horse to ?infest, they can’t mature and will die.
  • Do fecal egg counts and deworm new horses, if needed, before letting them share pastures and paddocks with others. Ideally, put them in a quarantine paddock for two weeks after treatment.
  • Remove bot eggs on your horse’s coat by clipping hair or washing with warm water. Bot flies lay the eggs in late summer and early fall; horses ?ingest the larvae as they hatch.

Applying these concepts will help protect your horse from parasites now. And by cutting back on the ?indiscriminate use of medication, you may delay the day when superworms show up.

Dianne Little, BVSc, PhD, MRCVS, DACVS, is currently a postdoctoral ?fellow in equine orthopedics at the North Carolina State University College of Veterinary Medicine. She has also done colic research as part of the ?Carolina Colic and Digestive Disease program at NCSU.

This article was reprinted from the May 2007 issue of Practical Horseman magazine.

For more information on deworming, check out Deworming Your Horse: How to Find the Best Deworming Schedule for You and Your Horse, a free guide from MyHorse Daily.Save

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Equine Vaccination Recommendations & Annual Horse Health Chart https://practicalhorsemanmag.com/health/vaccination-recommendations-and-annual-health-chart/ Fri, 13 May 2011 17:02:04 +0000 http://ci0202786a500e272a

The American Association of Equine Practitioners has four “core” equine vaccination recommendations that EVERY horse should receive?tetanus, Eastern/Western equine encephalomyelitis, West Nile virus and rabies?and a slew of others based on risk factors. Find out which equine vaccination recommendations are right for your horse at different ages and stages. Download this PDF chart with equine vaccination recommendations and our handy annual health chart, which allows you to record your horse’s vaccinations, deworming program, farrier visits, dentist visits and more.

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Download the Equine Vaccination Recommendations and Annual Horse Health Charts PDF

To learn how to give IM injections, see “Administering Injections: Should or Shouldn’t You?” in the June 2011 issue of Practical Horseman magazine. Click here to find out how to time your horse’s vaccinations in the article “Time Your Horse’s Vaccinations for Safer Results.”

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