Rethinking Deworming Strategy

Deworming by fecal egg count (FEC) is advocated as a way to avoid overexposure of parasites to deworming drugs. It’s important to understand the effect of deworming by FEC is primarily to minimize environmental contamination, not optimally protect the individual.

Young horses, PPID horses and seniors in general are at high risk for parasitism. Even some young adult horses have poor parasite resistance.  Much damage is done by immature forms that are not even laying eggs yet.

The problem with FECs is their limited capacity to detect parasites.

– they only reflect adults that are actively laying eggs at the time of the test
– egg-laying activity may vary seasonally
– tapes often missed because eggs are laid in packets/segments, not evenly mixed in the manure
– can’t detect tissue forms or immature stages in the lumen but these can be the most harmful for the host
– bots missed
– pinworms missed (lay their eggs on the perianal skin)
– Strongyloides in adults not detected

None of that matters in terms of herd health because small Strongyles are the major threat and the only mode of transmission is contamination of the environment by fecal shedding, but it sure matters to the individual.

The other problem is technical limitations. Samples sent through the mail are useless. Samples not collected as soon as they are passed then kept cold are likely inaccurate. The reason is that eggs hatch and flotation methods do not pick up larvae.

As for resistance, helminths come equipped with drug metabolizing enzymes which in some individuals transform the dewormers to harmless compounds. Obviously those genetically fortunate enough to possess those enzymes are the most likely to become resistant by upregulating enzyme activity when they are exposed to the drug – if it doesn’t kill them first.

Any parasitologist will tell you the major way resistance develops is underdosing. (Ditto for antibiotics and bacteria.) What doesn’t kill them makes them stronger. Frequent exposure can cause a dewormer to go from a 20% failure rate to 80% or higher.

It’s also true they can’t be fully resistant to a drug they have never been exposed to so there is an argument in favor of not automatically exposing parasites to a variety of dewormer drugs (rotation).  On the other hand dead parasites do not develop resistance or pass it on to their descendants.

In any case,  it’s wise not to attempt to deworm with drugs that are known to have widespread resistance in the species you are treating. This includes the following reported resistances:

  • Roundworms (Ascarids): Ivermectin, moxidectin, pyrantel
  • Strongyles: Fenbendazole, pyrantel, albendazole
  • Pinworms:

Last but far from least, there is growing evidence that the practice of only deworming by FEC is leading to reemergence of Strongylus vulgaris – “bloodworms”.

These are the large Strongyles which do significant damage to the intestine and arterial system when they are migrating. Back when I was starting out as a veterinarian we still had to deal with many horses with S. vulgaris damage and it wasn’t pretty – severe recurrent colic, intestinal infarction, debilitating lameness, even to the point of euthanasia. If you wait to see the eggs in feces, it may be too late. Regular deworming with ivermectin or moxidectin had all but wiped them out.

Deworming strategies have gone from one extreme to another – from frequent, regularly scheduled treatments to deworming only on evidence of egg-laying adults on FECs.  Neither is ideal.  Speak to your vet about developing a program that is optimal for your individual horse.

Eleanor Kellon, VMD

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Canine DCM Again

For those of you following the alleged connection between dilated cardiomyopathy and canine dog foods, finally a voice of reason:

Also nice to see carnitine finally mentioned.

Eleanor Kellon, VMD

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Tendon and Ligament Care

Tendons and ligaments are specialized forms of connective tissue. Tendons connect muscle to bone. Ligaments are anchored only to bone at each end.  Both are composed of interwoven strands of type I collagen protein in a structure much like a rope. They are built to resist stretch but both structures do stretch.

The force experienced by tendons and ligaments is a product of weight and speed

Tendons facilitate movement by pulling on bones when a muscle contracts. Stretching that occurs (e.g. when the fetlock drops during weight bearing) has an effect similar to pulling on a rubber band. When the stretch is released the tendon snaps back to its original length and this assists the pull of the  muscle. Ligaments are meant to restrict movement. They are able to dissipate their stretch because they contain strands of elastin, a protein which can deform then resume it’s original shape.

Overstretching can damage any tendon or ligament. Fatigue and working in deep footing are further risk factors, as are toe grabs or overly long toes and shoes with bars or heel extensions which delay breakover. Age and PPID (Cushing’s disease) also weaken these structures.

On the nutritional end, adequate protein in general is needed for connective tissue health and maintenance. The essential amino acid lysine is especially important because strengthening linkages in collagen and cross-links in elastin occur where lysine is located in their structure.

Vitamin C and copper are two nutrients critical to maintaining the integrity and strength of these tissues. Magnesium deficiency has been found to cause a dramatic reduction in the protein content of tendons. Collagen from animals with vitamin E deficiency is deficient in strengthening cross-linkages. Zinc deficiency slows the rate of collagen production.  A good broad based supplement that provides these nutrients, many of which are commonly deficient, is an inexpensive and common sense way to support the health of  tendon and ligament tissue.

Research has discovered that nitric oxide is critical to processes that maintain the normal integrity of tendons and ligaments under and after stress. This is particularly important for athletic horses. The herb Jiaogulan is potent support for the generation of nitric oxide in pathways that help promote homeostasis and healthy tissue.

Tendons and ligaments also benefit from good old-fashioned hands on care. Exercise is normally accompanied by a degree of inflammation. This is how tissues receive the signal to strengthen their structure and antioxidant defenses. The process is temporary but sometimes causes discomfort, heat and edema.

Simply massaging the area or water therapy with pressure is soothing  because it facilitates blood delivery to the tissues. Adding a liniment with the right ingredients can boost the benefits:

  • Aloe vera, Chamomile, Arnica and Comfrey are proven to contribute to the homeostatic balancing of inflammatory reactions
  • Lavender essential oil gently supports circulation
  • Rosemary extract has documented antioxidant properties

Tendons and ligaments play critical roles in the musculoskeletal system. Feed them well and treat them kindly.

Eleanor Kellon, VMD

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Obesity and Metabolic Problems

The vast majority of us are well familiar with how easy it is to gain weight with the wrong foods or simply too much food and how hard it can be to lose it. The same is true for most horses.

Being overweight does not mean your horse has a metabolic issue

In people, it is generally accepted that weight gain can lead to the development of insulin resistance and type II diabetes but that’s where parallels with the equine situation end. As obesity develops in people, so does a clear picture of higher inflammatory cytokines circulating in their blood and increasing insulin levels reflecting insulin resistance. This does not hold true for horses.

Banase et al [2016] found that markers of inflammation in skeletal muscle were actually lower in horses that were obese, and lowest of all in obese horses with elevated insulin – the exact opposite of what would be expected in a human.

What about obesity causing high insulin and equine metabolic syndrome? Nope. Lindase et al [2016] induced obesity in horses that already had moderately elevated insulin by feeding additional fat but the resultant 10% weight gain did not worsen insulin resistance.  Similarly, Bamford et al [2016] studied normal horses and induced obesity by feeding excess fat with or without a once daily high simple carbohydrate meal. Again, the weight gain did not result in insulin resistance in either group. Contrary to expectations, the horses receiving the high carb meals actually had better insulin sensitivity. [This has also been reported in earlier studies and represents an adaptation to the higher carbohydrate feeding.]

If obesity doesn’t cause EMS, where did that idea come from? As above, there is a connection in people but it’s also true that you will find a higher percentage of obese horses with abnormally high insulin than in horses of normal weight.  However, the reason for this is that horses with insulin resistance gain weight more easily, not because the weight gain causes EMS – a good reminder that association is not causation .

This doesn’t mean you can just ignore it if you horse is overweight. Excess weight puts a lot of unnecessary strain on the heart and skeletal system, reduces exercise tolerance, makes it more difficult to breathe and interferes with temperature regulation in the heat or when exercised.  These all improve with weight loss. The effects of weight loss on insulin sensitivity are not as clear.

Studies have shown reduction in baseline insulin  and/or insulin resistance with weight loss induced by diet and/or exercise but they differ in regards to whether there is a difference in effectiveness between dieting versus exercise. Comparing the studies is complicated by different breeds, horse versus pony, different diets and different degrees of weight loss. Suffice it to say that weight loss won’t hurt the situation with EMS and might help, particularly if exercise is included.

Obesity per se does not cause laminitis either – high insulin does. Being normal weight won’t protect from laminitis or guarantee normal insulin, but a normal weight in conjunction with a physiologically sound trim will certainly help to mechanically reduce the damage it causes.

In the chicken or egg world of obesity and EMS, it’s the EMS that comes first.

Eleanor Kellon, VMD

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Nervous System Support

A horse embodies grace, power, balance and movement.  Nothing is more potentially devastating than nervous system dysfunction involving brain, spinal cord or nerves. I’m often asked about ways to nutritionally support the nervous system.

A horse embodies grace, power, balance and movement

Vitamin E is something most people equate with nervous system health, and with good reason.  The neurons which make up the nerves, spinal cord and brain are very high in fat. Fat is highly vulnerable to damage from oxidative stress and vitamin E is the premier fat antioxidant. Vitamin E actually becomes directly incorporated into the fats of the nerve cell’s  membrane.

Vitamin E deficiency alone causes reproducible malfunctioning of the nervous system. Because of the key role it plays, and the involvement of oxidative stress under many different scenarios,  vitamin E supplementation is also recommended to support the nervous system when there is any sort of stress to this tissues.

As a fat soluble vitamin, E also needs fat to be absorbed. Supplemental E is ideally fed dissolved in oil. There are altered forms available which are water soluble and easy to absorb but they are very expensive.

Acetyl-L-carnitine [ALCar] is a nutrient naturally produced from L-carnitine in the cell’s mitochondria. Like vitamin E, it is in very high concentration in the nervous system. ALCar in nerves is another antioxidant but it does even more.  ALCar helps maintain levels of nerve growth factor which facilitates maintenance and repair of nerves.  ALCar is particularly important in helping to maintain the health of myelin, a material which forms a protective sheath around nerves and plays a role in the transmission of impulses along the nerves.

Antioxidants in general are excellent support nutrients for the nervous system both due to its high fat content and high levels of energy generation with resultant oxidative stress. The nervous system is also very sensitive to oxidative stress from toxins.  Among the useful antioxidants are:

  • Herbals such as Devil’s Claw, Turmeric, Ginkgo biloba, Boswellia, Oregon Grape and Grape Seed Extract
  • N-acetyl-cysteine
  • Vitamin C and citrus bioflavonoids including quercetin
  • Alpha lipoic acid
  • Resveratrol

Last but far from least is to make sure your horse’s diet has a solid foundation by matching your amino acid/protein, essential fatty acid, vitamin and mineral supplements to the type of diet and its mineral profile.

Solid nutritional support can help your horse rise to meet challenges to his nervous system health.

Eleanor Kellon, VMD


















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Special: Update on Garlic and Horses

Garlic has a long history of possible health benefits but its safety has been questioned because other members of the Allium family (i.e. wild onion) are known to potentially cause hemolytic anemia.

In 2005, Pearson et al published a study showing doses above 200 mg/kg (3.2 oz for a 450 kg/990 lb horse) for 71 days could cause “hematologic and biochemical indications of Heinz body anemia, as characterized by increases in Heinz body score (HBS), mean corpuscular volume (MCV), mean corpuscular hemoglobin, platelet count, and serum unconjugated and total bilirubin concentrations and decreases in RBC count, blood hemoglobin concentration, mean corpuscular hemoglobin concentration, and serum haptoglobin concentration.”

Heinz bodies are small bubble-like structures on red blood cells. They form after oxidative damage to hemoglobin. Garlic interferes with an enzyme system that normally protects hemoglobin from oxidative stress.

That dosage had been voluntarily consumed but is larger than would typically be fed as a supplement. I had also  had personal experience with hemolytic anemia developing in a barn of horses being fed 1 to 2 kg/day of a commercial feed  containing garlic in an undisclosed amount. Anemia resolved upon stopping the feed.

Most recently, Saastamoinen et al reported that 83 days of feeding as little as 32 mg/kg (1/2 ounce daily for a 450 kg/990 lb horse) also caused slight decline in hemoglobin, hematocrit and red blood cell counts compared to matched control horses not fed garlic. Unfortunately, they did not check for Heinz body formation, bilirubin or haptoglobin so it is difficult to draw direct comparisons. .

While the changes found by the 3 month study of Saastamoinen et all were relative small, so was the dosage used.  Horses will vary in their sensitivity to garlic’s effects but it is clear that doses of garlic much smaller than previously thought may cause red cell changes. If you are feeding garlic long term it is wise to monitor for Heinz body formulation and changes in red cell count and parameters.

Eleanor Kellon, VMD


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Abductive Reasoning – Not Enough for Diagnosis

This blog first ran in 2013 – it still holds true.

You’ve heard “If it walks like a duck, quacks like a duck…… it must be a duck”.  That is an example of abductive reasoning, more accurately inference, where a set of observations leads directly to a conclusion.  However, that conclusion is just a best guess and the duck example should really end with “…it could be a duck”.  That’s more than just splitting hairs.  Depending on exactly which characteristics were used to conclude the bird is a duck, you could actually be looking at a coot or a loon.

In contrast, a proper medical diagnosis always involves deductive reasoning somewhere along the line.  Subjective (observations) and objective (firm data like radiographs or laboratory tests) findings are assembled to come to a hypothesis, which is further tested and refined as much as possible.  To increase the chances your duck is actually a duck you could look for physical characteristics unique to ducks, examine nests and eggs, do DNA analysis, etc.

Some diagnoses are easy. A horse standing on three legs with the edge of a bone protruding through the skin of the fourth leg obviously has a fracture.  With nothing protruding through the skin all you have for sure is a horse standing on three legs.  Pain as the reason is on the top of the list, with fracture a possibility under that although could be abscess, nail in the foot. Severe neurological or muscular injury could also be preventing the horse from using the leg.

The picture is even less clear when signs are vague.  Trouble holding feet up, doesn’t want to canter, bucks, sensitive to touch, poor muscling, lethargy, etc. could fit problems with many systems and different disorders. You have to dig deeper.

We once had a horse come in for training whose gaits behind would get progressively worse the longer he exercised.  Watching him generated lots of opinions.  “It’s OCD.”  “It’s EPM.” “He’s tying up.”

Blood work was normal.  Lameness exam with nerve blocks up to and including the stifle did not change him.  I did a rectal exam and thought his iliac arteries felt thickened with weak pulses so sent him to a referral clinic for a rectal ultrasound.  The clinician there ignored the history, watched him jog up and down a road and proclaimed “It’s stifles”.  He even threw in “If it walks like a duck…..”.  Several hours and a few hundred dollars later, after negative stifle radiographs and painstaking stifle ultrasounds, the rectal ultrasound was done.  Thrombosed iliac arteries.

It happens all the time with first impression diagnoses.  EPM and reluctance to move called laminitis.  Laminitis misdiagnosed as tying up or hock lameness.  Horses with severe colic pain looking neurological.  Those things at least will (or should) get straightened out pretty quickly by a careful physical exam.

Too many horses suffer needlessly because they are not diagnosed properly.  Signs and symptoms alone are rarely enough.  They get lengthy and even expensive courses of treatment for EPSM, EPM, gastric ulcers, “hindgut ulcers”, “sugar sensitivity”, subclinical acidosis, leaky gut, environmental toxins and on and on with no improvement because a diagnosis was never actually confirmed.

If it walks like a duck, prove it’s a duck.

Eleanor Kellon, VMD

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Struggling Lungs

ProAir, Vitamin C, Lung EQ, Spirulina

Most of your horse’s body is heavily oriented to minimizing contact with the rest of the world but the lungs rely on it to function.  This makes their job of extracting oxygen and releasing carbon dioxide and other wastes very high risk.

From draft work to speed, and just staying alive, all cells depend on oxygen extracted by the lungs

For gas exchange to occur, the tissue must be very thin, only one cell thick. The challenges this fragile organ faces include infectious organisms, noxious gases, physically irritant particles and potential allergens. There are even immature forms of some parasites which travel through the lung.

The first line of defense is a mucus layer on all surfaces. This traps potential irritants and is a barrier to invaders. There is a rich antioxidant system to both combat incoming problems and protect the tissues from immune system responses. The local immune system is robust but may also be triggered to have strong reactions against irritants and potential allergens.

Even the weather can be a problem. Hot summer air that is heavy with humidity suspends and concentrates irritants. It also increases the work of breathing. Cold and dry winter air reduces exposure to environmental irritants but tends to dry out the mucus barrier and  causes bronchospasm in some individuals.

There are some key supplements you can use to support lung health and normal function. Spirulina is a fresh water, nontoxic, blue-green algae with some unique properties. In addition to excellent antioxidant capacity, Spirulina helps maintain balanced immune function and antibody production as well as stability of the mast  cells which store histamine.

Jiaogulan (Gynostemma pentaphyllum) is a Chinese vine with many health promoting properties. Of interest here is assistance in maintaining relaxed, open airways.

Vitamin C is a major antioxidant in the lung and known to be in high concentration in lung tissues and secretions. MSM and Grapeseed meal and extract are also potent antioxidants in the respiratory system, while citrus bioflavonoids both help bolster antioxidant defenses and contribute to the health of the fragile network of capillaries where gas exchange occurs.

Finally, there are important steps you can take to minimize exposure to irritants. Keep the horse outside as much as possible.  When stabled, maintain good airflow through the building. Use wood or paper bedding rather than straw. Remove urine soaked bedding frequently as bacteria will break it down to irritating ammonia. Wet down all hay and bucket meals before feeding.  Do not store hay or straw in the same building as the horse. If ground conditions in the arena or ring are dusty, hose it down before riding.

Supporting healthy lung function can be a challenge but a combination of appropriate supplementation and environmental management can go a long way toward achieving easy breathing.

Eleanor Kellon, VMD



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The Seasonal ACTH Rise

ACTH, adrenocorticotropic hormone, is produced by the pituitary gland. It’s function is to trigger cortisol release from the adrenal gland.  Every year in the fall there is a temporary increase in the amount of ACTH produced. For most horses this is a relatively small increase and does not cause any problems.  However, for horses in the early stages of PPID [pituitary pars intermedia dysfunction, aka Cushing’s Disease], it can mean disaster.

Autumn is dangerous for horses with undiagnosed early PPID

The classical and most obvious outward signs of PPID are muscle wasting, sagging abdomen and a long, often curly coat that does not shed normally.  However, these develop relatively late in the course of the disease and PPID  can be present for many years before they are seen.

Abnormally  high ACTH levels are a laboratory marker of PPID but in early cases may be normal for most of the year. When the seasonal ACTH rise hits, these early PPID cases go into overdrive and generate levels much higher than the usual rise in healthy horses.

ACTH stimulates the adrenal gland to produce cortisol. Cortisol in turn causes insulin resistance. This can result in an unexpected case of laminitis, often the first of the horse’s life. Horses that already are EMS cases are at particularly  high risk of developing insulin levels high enough to cause laminitis but it can happen  to horses without a history of EMS too.  An unexplained autumn laminitis is often the very first sign of PPID.

There are some other signs of an abnormally high ACTH rise. Look for:

  • Sudden increased water consumption (often doubles)
  • Increased urination
  • Filling of the fossae above the eyes with fat
  • Development of a fatty crest – or worsening if already there

The seasonal ACTH rise starts with minor increases that ramp up slowly starting end of June. The upward climb accelerates in September and peaks last week in September, with some minor variability depending on exact geographical location. Horses in the early stages of PPID experience exaggerated rises and problematic levels can be found as early as July in some horses.

If you see signs suggesting ACTH elevation may be excessive, call you veterinarian and do blood work to check. It may be suggested to start treatment with pergolide even before the blood results are in. Its important to understand the laminitis and other changes can only be controlled by removing the cause – the high ACTH. That is what the pergolide does.  No amount of diet manipulation, supplements or anti-inflammatory drugs is going to make a difference if you don’t address the root cause.

If your horse is in his/her teens or older and develops unexplained laminitis in late summer/fall, be sure early PPID is on your list of possible causes and check ACTH. A correct diagnosis is the road to correct treatment.

Eleanor Kellon, VMD


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Feet in the Heat

Throughout history, horses have been able to perform and thrive in very hot, even desert, environments. Breeds such as the Arabian, Akhal-Teke and predecessors like Turkoman and Byerly Turk are among the many desert adapted breeds.

Healthy hooves withstand dry, hot weather without cracking

Sand is about as dry and abrasive an environment as you can get. To make things even worse, did you know that dirt or sand will be as much as 40 degrees Fahrenheit hotter than the air temperature?  Obviously the success of desert breeds shows it takes more than hot dry weather and surface conditions to cause hoof problems. A further example of hooves’ resistance to heat is that experimentally putting blocks of hoof wall in a 140 degree Fahrenheit (60 C) oven for 2 weeks causes no change in the outer protective permeability barrier.

A major function of the hoof wall is to hold its natural moisture in while sealing excess moisture from the environment out. This is accomplished through incorporation of a variety of fats – fatty acids, waxes, cholesterol and ceramides. Poor quality of this fatty matrix surrounding and covering the cells leads to hoof dryness and cracking.

The horse’s natural protective shield can also be disrupted mechanically. Rasping the dorsal hoof wall is a common practice but it’s asking for trouble, especially in extremely hot and dry weather. The outer few cellular layers are critical to the moisture barrier. Nails from shoes mechanically disrupt the barrier function.

Stress cracks develop from unbalancing trimming or going too long between trims and allowing the hoof to become overgrown.  The strength and quality of keratin protein in the horn tubules also influences how easily the hoof wall flares, deforms and  cracks as it grows. Whatever the cause, once the integrity of the hoof wall is breached, it will rapidly dehydrate.

The difference between horses whose hooves stay healthy in hot and arid conditions versus those that dry, crack and peel is quite simply the health of the hoof.  Research has shown that the function and strength of the barrier fats in the hoof is strongly influenced by the ceramide content. That, in turn, responds to biotin supplementation. The requirement of the horse is unknown but research has shown favorable response to a dose of 20 to 30  mg/day for the average horse.

The horse is capable of synthesizing all the fats needed for the hoof wall with the exception of essential fatty acids. No dietary minimum requirement has been set for fat in the equine diet but supplemental fat often noticeably contributes to coat and hoof quality. Other key nutrients for the hoof wall include the vitamin pyridoxine, essential amino acids methionine and lysine as well as trace minerals.

Topical hoof dressings are no substitute for a healthy hoof but if you find your horse is in trouble they can be helpful while you work toward maximizing hoof nutritional support. Pair a good penetrating oil like Neatsfoot with glycerin and vegetable oils to boost barrier function. Turpentine, Yucca and Aloe Vera may help ease temporary sole tenderness. Iodine and essential oils help support healthy microbial levels and good circulation.

All is not lost if your horse’s hooves become dry and brittle in the heat. Careful attention to sound nutrition and temporary use of a good dressing to boost barrier function can get hoof health back on the right path.

Eleanor Kellon, VMD







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