Lead Feature

in large strongyles, and early indications of resistance in roundworms.

Macrocylic Lactones – generic names: ivermectin, moxidectin; brand names: Ivermectin, Zimectrin, Zimectrin Gold, Quest Gel, Quest Plus Gel, Ivercare –early indications of resistance in small strongyles, no resistance in large strongyles, and widespread resistance in roundworms.

Pyrimidines – generic name: pyrantel pamoate; brand names: Strongid, Exodus, StrongyleCare, Equi-Mintic, Equi-Aid –common resistance in small strongyles, no resistance in large strongyles, and early indications of resistance in roundworms.

If you drag a pasture/spread manure on a live [actively grazed] pasture, you’re actually doing the parasites’ job for them and helping them travel.

Isquinoline-pyrozines – generic name: praziquantel; brand names: Quest Plus Gel, Zimectrin Gold – no resistance known.

There’s considerable concern about the eventuality of worms becoming resistant to virtually all the drugs currently available. In parts of South America, Australia, and South Africa, large sheep ranches went out of business because worms on those ranches became resistant to every drug available. The eventuality is rather frightening, because theoretically, worms should develop resistance to just about any dewormer.

So what’s a horse owner to do?

The Lowdown on Egg Loads

Successful defense begins by working with your veterinarian and diagnosing which parasites your horse is carrying.

Fecal Egg Count Test

A fecal egg count test, (two types are recommended by the AAEP: Modified McMaster Procedure and Modified Wisconsin Technique), quantifies the number of eggs per gram of manure. If the infecting parasites are at the stage in their life cycle when they are producing eggs, a fecal egg count can help estimate the worm burden. The fecal egg count test does not tell you the worm burden in the horse, but the number of eggs being shed by those worms. From there, one infers the parasite load in the horse.

For example, horses with small strongyle egg shedding of 0 to 200 eggs per gram are considered low (pasture) contaminators; 200 to 500 eggs per gram are moderate contaminators; and eggs per gram of 500 or more are high contaminators — shedding the most eggs in your pasture, paddocks, and stalls. If you have multiple horses, 20 percent of your horse population passes about 80 percent of all parasite eggs on your property.

In our Massachusetts climate, test adult horse’s manure in the spring when the grass begins growing and again in the fall after the first hard frost. Horses should not have received dewormer treatment at least eight weeks prior to the sample, preferably 12 weeks.

Since we have cold winters here in the Bay State, you won’t need to deworm adult horses during the winter because the cold prevents parasites from developing into an infective stage.

Once you’ve tested an adult horse several times to determine his shedding status, his classification as a low, moderate, or high contaminator is unlikely to change.

Foals, yearlings, and young horses have higher burdens of parasites and are much more susceptible to disease. As young horses age, their immune system is better equipped to eradicate worms. Consult with your veterinarian if you have a youngster on your hands as they carry more roundworms and need a specialized fecal egg count and deworming schedule.

Horses more than 20 years of age tend to have special parasite control needs as they are typically high shedders. Work closely with your vet to determine the best practices for your elderly horse.

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Fecal Egg Count Reduction Test

A fecal egg count reduction test — running a fecal egg count before and after administering a dewormer — can help your veterinarian assess the efficacy of the dewormer used and identify the possibility of parasite resistance on your farm.

The test involves comparing the fecal egg count in a fresh manure sample, taken the day a horse is dewormed (before deworming), with a second sample, analyzed 10 to 14 days after deworming.

Although egg counts can vary, if the second egg count has not decreased by at least 98 percent compared to the first for ivermectin and moxidectin and at least 90 percent with other dewormers, it’s likely that your dewormer isn’t doing its job and/or your parasites have developed resistance.

For dewormers that are effective with your horse, recheck about every two years with a fecal egg count reduction test to be sure their effectiveness has not decreased.

If a fecal egg count reduction test suggests your product is working effectively, use it. If not, discuss with your veterinarian the next steps for your horse and farm.

It’s easy to keep using the same products for years — maybe because there’s no reaction in your horse. But it’s also possible that no reaction means no parasites are being killed. They could be resistant, and without a test, how would you know?

Wrapping Up Tapeworms

What a fecal egg count will not pick up is the presence of tapeworms, because tapeworms shed eggs only sporadically. Grazing horses become infected when they ingest, while on pasture, mites that have consumed tapeworm eggs from the manure of infected horses. The most common species reach about two inches as adults, whereas others grow upward of 30 inches long.

Tapeworm segments are usually not detected in manure, so infection won’t be obvious until the horse is in surgery or has died. The most deadly colics are often a result of these parasites. In addition to colic, tapeworms can also cause unthriftiness and diarrhea.

How can you confirm if tapeworms have infected your horse? A saliva test that determines your horse’s tapeworm burden is now available. Previously, the most reliable method of identifying tapeworms was a blood test to measure antibodies specific to tapeworms.

The new test, EquiSal Tapeworm, works by identifying levels of tapewormspecific antibodies in your horse’s saliva. The saliva test is just as accurate as the blood test at predicting the presence of tapeworms, and it can also predict the severity of the infestation. A higher saliva score indicates that your horse is carrying a larger number of tapeworms. EquiSal is not available in the U.S. However, U.S. labs will be able to conduct the test early in 2019.

Since fecal egg counts only identify small strongyle and roundworm burdens, once a year (the fall, after the first hard frost, is a good time), administer a dewormer that is also effective against tapeworms to adult horses.

What You Can Do

Good stable management is the first and best line of defense because inevitably parasites will find their way into the intestines of almost every horse. What exacerbates the problem are conditions that perpetuate high parasite loads: overcrowding horses on pasture, not cleaning stalls and paddocks to minimize fecal contamination, and not tracking parasite loads, not only in your current horses but in new arrivals as well.

Parasite control boils down to a deceptively simple, three-step strategy.

Strategic Deworming

First, decrease the number of egg-laying, adult parasites by running fecal egg count tests and fecal egg count reduction tests and deworm horses based on findings and your veterinarian’s recommendations.

All horses on a farm should be

Fecal Egg Count Testing Schedule

horse’s age

youngsters fecal egg counts fecal egg count reduction test routinely to determine annually until more roundworms than two years old deworm

deworm foals for roundworms, after weaning focus on small strongyles, tapeworms

adults once or twice per year every three years for each dewormer drug class used deworm spring and fall after first hard frost, additionally for high egg shedders as needed

elderly same as adults, every three years for some elderly horses each dewormer drug are high egg shedders class used same as adults

new horses upon arrival same as adults

Fecal egg counts help you know your horse’s level of worm egg shedding. Collect a manure sample prior to deworming.

Fecal egg count reduction tests are the only way to know if your dewormer is effective. Perform a fecal egg count before deworming, deworm the horse based on results, and perform another fecal egg count 10 to 14 days after deworming.

included on a deworming schedule.

The way you deworm has to be strategic. The goal is not to eradicate worms entirely in your horse, but to reduce the number of eggs your horse is shedding to reduce pasture infection.

Pasture/Paddock Management

Next, get rid of larvae and eggs your horse could ingest by removing manure from all feeding areas. The pickup and disposal of manure yields dramatic results and longer intervals between needed deworming — an important benefit considering the increase in drug resistance by parasites.

If you remove manure within 48 hours from paddocks and pastures, there’s considerably less risk of contamination. Don’t drag pastures with manure unless you’re rotating horses to a different pasture and spreading manure on a pasture where horses will not be grazing. Spreading manure exposes the manure to air, heat, and light, which will destroy parasite eggs IF the temperature is above 77 degrees for a few weeks or above 104 degrees for a few days. If you drag a pasture/spread manure on a live [actively grazed] pasture, you’re actually doing the parasites’ job for them and helping them travel.

Notice the “rough” areas of your pastures and paddocks, the places the horses use as “toilets.” The majority of horses will defecate in these areas and will not graze on the grass that grows in these areas. This is to avoid the ingestion of parasite eggs. (One of my Haflinger mares didn’t get this evolutionary memo and grazes in the

rough areas. As a result, she’s a very high egg shedder.)

When you drag a pasture where horses will be grazing before the eggs are destroyed by air, heat, and light, or feed hay where there’s manure, you’re forcing your horses to eat in their “toilet” and increasing the number of worm eggs your horse ingests.

New Arrivals

When a new horse comes into a barn it should be stalled away from others for two weeks, which is enough time for any viruses in transit to go away. Begin a fecal egg count reduction test the day you deworm the horse (upon its arrival at your farm). Collect all manure from both the stall and isolation paddock. Be sure the manure goes off the farm, directly into compost, or is plowed under on crop fields. At the appropriate 10 to 14 days after the initial fecal egg count test, do another to finalize the fecal egg count reduction test. You want to be sure the dewormer used was effective and that the new horse’s parasite load is known prior to introducing this horse to turnout buddies where he could contaminate your pastures, paddocks, and your horses with egg shedding.

Dosages and Weights

Deworming results will be only as good as its application. Giving a horse an adequate dosage can be a big challenge. Horses can hold paste in their mouth for five minutes before spitting it out. Not all paste dewormers are particularly palatable, and it can be a challenge to get your horse to swallow it. If you can administer a flavored paste, you’re likely to be more successful.

The critical step is in the dosage. Most horse owners are familiar with using a measuring tape to get the heart girth measurement to estimate the weight of their horse. Although muscle weighs more than fat, using a tape is a good place to start. However, there’s a more

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accurate way to estimate the horse’s weight.

Weight tapes use a horse’s heart girth measurement alone, but by adding body length to the heart girth measurement you get a more accurate weight for horses older than one year.

Measure the heart girth — the midsection of your horse, immediately behind the elbow and withers. Next, measure from the point of the shoulder to the point of the buttock. Then, use this equation: (heart girth x heart girth x body length) divided by 330. For a weanling divide by 280 and for a yearling, divide by 301.

Now you have a more accurate weight for your horse.

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.

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 amount of pounds more than you think your horse weighs. Your vet may suggest that if your horse weights 1,100 pounds, you dose the horse for 1,250 pounds.

When it comes to foals, smaller ponies, and Miniature horses, however, overdosing can become a problem, so you should always consult with your vet before determining the appropriate dose, and take extra care during the actual administering to ensure that an overdose does not occur. Make sure that little stopper is firmly in place so you don’t mistakenly give a 250-pound Miniature horse a 1,250-pound dose!

What if your horse spits out some dewormer? 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 dewormer check to be sure he has no hay, grass, grain, or treats in his mouth.

It’s a good idea to have extra

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dewormer on hand in case more ends up on the outside of your horse's lips, on the ground, or on you than you expected. You want to be sure the correct amount all goes down the hatch, so to speak.

These drugs are not effective when given in small amounts over a period of time. The whole dose must be administered at one time. If your horse doesn't swallow his full dose within 12 hours, wait a few days and start over with a new plan and another full dose.

Rewarding your horse with his absolute favorite food after you are sure he’s swallowed the dewormer is one way to help him stay open to you putting dewormer and other medications in his mouth. I did this with my Haflingers from the time they were weanlings. Once they were about a year old, they got so excited to be dewormed that I had to be sure I kept the tubes and caps securely in my pockets. My horses have been known to try to eat the actual dewormer tube! This is because they anticipate their favorite food via the “treat bucket” after every deworming. (They also swallow the dewormer immediately in anticipation of said treat.)

Working with Your Veterinarian

A recent study in the United Kingdom found that deworming strategies were 75 percent more effective when veterinarians were involved in the deworming program.

There’s a lot more to it than just picking out a tube of paste from a shelf and hoping your horse is cured. Veterinarians are able to act as your horse’s health consultant. They do it every day, with each physical exam, with every animal. Not only can they advise on when to give

Equine Worm Guide

worm

bots

large strongyles, bloodworms population

all horses in summer

uncommon in adult horses

pinworms

roundworms

small strongyles widespread, less common in adult horses

widespread on breeding farms, foals, weanlings

widespread

tapeworms

threadworms horses more than six months of age

widespread symptoms

none, bothersome, a way for flies to breed resistance

none known

sever colic, blood clots in arteries, intestinal damage none known

tail rubbing, skin irritation around the anus some

airway inflammation, pervasive small intestine impaction, poor growth

weight loss, diarrhea, dull hair coat, poor performance, lack of appatite, lethargy

spasmodic colic, colic pervasive

none known

diarrhea, sometimes unthriftiness none known

dewormers, there are times when they will advise against it. This is just as important.

Today’s products have negated the need for such old-fashioned approaches as tube worming, but they’ve also disenfranchised veterinarians from the process.

Essentially, to stay one step ahead of the worms work closely with your veterinarian to customize a parasite control program — one that addresses the problem completely.

As parasites develop resistance to dewormers regularly used to treat against them, the answer is not to stop deworming our horses. What it does mean is that, whenever possible, we should deworm fewer times a year and select the deworming agent with care. Using fecal tests allows us to do just that, deworm less frequently and more accurately.

Continuing the old methods of deworming every two months, or whatever you may have done in the past that doesn’t include fecal tests, is contributing to the parasites’ ability to become resistant to the current dewormers.

As parasites evolve and develop resistance to dewormers, we too, as owners, must evolve in our efforts to come up with a better system of horse care, incorporating a closer relationship with our veterinarian, a more rotational cycle of dewormers, and more vigilant stable management protocols.

Stephanie is the publisher of Massachusetts Horse and Connecticut Horse. A lifelong horsewoman, she’s been a riding instructor and a breeding manager at an 80-horse Arabian farm where she foaled out mares, collected stallions, and administered the vaccination and deworming programs. Stephanie currently lives in the foothills of the Berkshires on Pocketful of Ponies Farm.

Dewormers Demystified

BENZIMIDAZOLES generic names: fenbendazole, oxibendazole brand names: Panacur, Safe-Guard, Anthelicide EQ effective against: large and small strongyles, encysted small strongyles, roundworms, pinworms resistance*: prevalent in small strongyles in Southeast, early indications in roundworms

MACROCYCLIC LACTONES generic names: moxidectin, ivermectin brand names: Quest, EquiMax, Zimectrin, Equimectrin, IverEase, IverCare, Rotectin effective against: large and small strongyles, roundworms, pinworms, bots resistance*: early indications in small strongyles, widespread resistance in roundworms

PYRIMIDINES generic name: pyrantel pamoate brand names: Strongid, Equi-Aid, StrongyleCare, Equi-Mintic, Exodus effective against: large and small strongyles, roundworms, pinworms, bots resistance*: common resistance in small strongyles, no resistance in large strongyles, early indications in roundworms

ISQUINOLINE-PYROZINES

generic name: praziquantel brand names: Quest Plus Gel, Zimectrin Gold effective against: large and small strongyles, roundworms, pinworms, bots, tapeworms, threadworms resistance*: none known

* Based on information for the southeastern states that have been studied. No studies yet in Northeast.

Trail Guide

Danbury Tarrywile Parkby Stacey Stearns

Tarrywile Park and Mansion in erty. Equestrians from the stable often ride Danbury is a renowned wedding in the park and enjoy the trails. and event location. However, the Lucy Prybylski owns and operates 722-acre treasure also has 21 miles of Happy Trails Farm with her husband, Ed, trails that are open to hikers, nature and enjoys western dressage, ranch ridenthusiasts, and equestrians. Tarrywile ing, and trail riding. She serves on the Lake, Parks Pond, and Back Pond add to board of the Friends of Tarrywile Park the beauty of the location while attracting and the Newtown Bridle Lands local anglers. The city of Danbury pur- Association. chased the land in 1985, and the “It’s important for equestrians to be Tarrywile Park Authority manages it as a active in trail organizations so we can con-

passive recreation and education area.

Riding here reminds you of a different era and way of life. Large estates such as Tarrywile were once commonplace, and although we’ve all seen it in the movies, riding through Tarrywile and imagining how people once lived is a unique experience.

Tarrywile is a hub of activity and connects community members across all spectrums. Other passive recreation at Tarrywile includes hiking, cross-country skiing, orienteering, scouting events, cross-country running, and primitive camping.

Happy Trails Farm is located on Mountainville Road in Danbury across from the eastern side of the Tarrywile prop-

Lucy Prybylski

tinue to have access to these places,” Lucy says. There are several equestrians who serve on the board of the Friends of Tarrywile Park. The Newtown Bridle Lands Association is dedicated to preserving equestrian and passive recreation trails.

History Lesson

Tarrywile Mansion was built in 1897 as a home for Dr. William C. Wile and is now on the National Register of Historic Places. It’s frequently rented out as a popular wedding and event location. Visitors can take a self-guided tour when there aren’t events. Rental proceeds help sustain park operations. The English-style garden surrounding the mansion attracts numerous visitors each year.

The grounds include a carriage house that was originally a stable before automobiles replaced horses, an apple orchard, icehouse, greenhouse, and gatehouse. An active dairy farm was on the property until the 1970s. You can still see the silo and milking parlor when you visit. Danbury High School has a garden project in the greenhouse, which helps students learn horticultural skills. Picnic tables and a gazebo in the orchard make it an inviting spot for park guests.

Tarrywile Lake was a drinking water reservoir for the city of Danbury, so the family had Parks Pond dug for their personal use. Footbridges around Parks Pond were built as Eagle Scout projects but are not suitable for horses.

Equestrians should also avoid the areas near the mansion. Hearthstone Castle, built in the 1890s, is on the eastern side of the park, but is supposed to be demolished. The castle has a long and unique history of its own. It’s currently fenced off.

A Leg Up

Download a map at tarrywile.com/ exploring. Click on TARRYWILE HIKING TRAIL GUIDE.

There are two parking lots at Tarrywile, one off Southern Boulevard, another off Brushy Hill Road. Horse trailers should use the larger lot off Southern Boulevard. From the parking area you can ride past the picnic area, Red Barn Environmental Education Center, milking parlor, and silo to the trails.

Parking is limited for horse trailers. “I recommend that equestrians come on a weekday and arrive early to ensure adequate parking,” says Becky Petro, the executive director of Tarrywile Park and Mansion. Clean up around your trailer before you leave, including sweeping up any hay.

Trails are open seven days a week from sunrise to sunset. Equestrians and other trail users can experience a variety of terrain across the 722-acres. There are large fields with spectacular views, while the terrain is rugged and rocky in other places. You’ll ride past ponds and natural blueberry and blackberry patches. Tarrywile is home to a plethora of plant and wildlife species; keep your eyes peeled for small animals, fun plants, and enjoy the chorus of birds as you ride along.

Out Riding It

Brushy Hill Road cuts through Tarrywile Park, and separates the trail system. Parking is on the western side of the park. Lucy and the boarders at her barn generally ride on the eastern side of the park, since that’s where they access the park. Fewer trail users are on the eastern side.

“A lot of equestrians use the park,” Lucy says. “They don’t want horses near the mansion, but with so many trails, it’s easy to avoid. We’re careful not to leave manure on the trails, and we only ride when the footing is good so that we don’t tear up the fields. It’s important for equestrians to take good care of the trails and land we access.”

From the silo and dairy barn the park unfolds before you as you’re standing in the hay fields. Loop around the edge of the fields, and then you have two options. Follow the edge of the field alongside Parks Pond and over to the orange trail to ride the eastern side of the park. Or, cross Brushy Hill Road to ride the orange trail loop. The location markers on the trail match your map. You can go left or right