Copyright 2011 by Brenda Bishop, VMD All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, without prior written permission of the author.

Abstract Shivers is a hind leg unsoundness (a spasmodic condition affecting the thigh muscles of the horse) that has been documented as early as the 1800’s primarily in certain draft horse breeds and draft crosses. Despite this historical record, many twenty-first century veterinarians fail to recognize and diagnose Shivers at best, a peculiar lameness is noticed for which there is no treatment coupled with the expectation of no improvement and a gradual steady decline in the horse’s usefulness. This in-depth look at Shivers abandons the conventional classification of ‘lameness’ and attempts to characterize and appreciate a broader definitive context, namely that of underlying autoimmune disease. Taking into consideration the clinical aspects of three stress- related immune mediated disorders (Myasthenia Gravis(MG), Lambert-Eaton Myasthenic Syndrome (LEMS) and Fibromyalgia Syndrome (FMS)), Shivers is redefined as a component of two autoimmune states traditionally labeled MG and LEMS in humans and as a potential development in horses with equine FMS. On the basis of this new approach to a centuries old problem, useful and effective nutritional treatment protocols are reported.

The average age of onset for Shivers is 2 to 4 years or older, and the vast majority of affected horses are male (geldings or stallions). Shivers is somewhat unique in that it manifests sporadically and only while standing and (eventually) at the walk, most obviously when walking in the backward direction. The blacksmith will frequently comment that the affected horse has unusual difficulty holding one or both hind legs up the affected hind leg will be held spasmodically in a hyper-flexed position for several seconds before being placed on the ground. Careful observation will reveal fluttering eyelids and ears and possibly a raised tail at the same time. Stress in any of its various forms will exacerbate the problem for example, work in excess of the horse’s fitness level, extreme summer or winter weather, traveling long distances, etc. There are many historical accounts of horses developing Shivers after a long train journey. Stress and Shivers are such intertwined partners it is hard to tell how, when or where one stops and the other begins. As the body’s immune system is pushed beyond its capacity to function in a healthy manner, the system goes into overdrive, a serious imbalance is created and the possibility of an autoimmune state arises.


When comparing multiple Shivers horses with each other it becomes abundantly clear that several clinical entities exist. If an effective treatment approach is to be formulated the management team (caretaker, veterinarian, blacksmith, body worker, nutritionist, etc.) should be informed with rudimentary knowledge of what goes on at the cellular level. Within the autoimmune category (an overly stressed immune system attacks some of its own body proteins producing antibodies), Shivers reflects a disease of neurotransmission, specifically at the neuromuscular junction (NMJ). At the NMJ, the neurotransmitter acetylcholine is released from small nerve endings, flooding the synapse between nerve endings and muscle receptors. When a sufficient number of acetylcholine molecules can attach to muscle receptors, there is an electric discharge of the normal membrane potential and the muscle fiber contracts. If many or most of these receptors are already occupied by antibodies, neuromuscular transmission is blocked. This blockade is happening at the end of the chain of transmission, a condition referred to as Myasthenia Gravis (MG). In MG not enough acetylcholine molecules find receptors to trigger normal muscle contraction. The muscle endures a delayed irregular seizure type contraction which is uncomfortable (not to mention frightening) for the horse and potentially dangerous for any human standing near the affected body part. MG in horses, dogs and cats is usually localized to the point of being organ specific and even tissue specific. For example, German shepherd dogs with MG will display an enlarged esophagus and difficulty swallowing. Horses with MG will primarily have painful muscle spasms and cramping in their inner thigh muscles, historically called Shivers. Deficits caused by acetylcholine receptor antibodies, skeletal muscle weakness, cramping within the inner thigh muscles and occasional sweating at rest characterize what could be called the ‘post-synaptic myasthenic horse’.

Current day symptomatic treatment of MG in humans, dogs and cats is based on knowledge of the synaptic transmission of motor impulses at the NMJ by acetylcholine. Conventional handling of MG uses drugs which inhibit cholinesterase and which therefore serve to promote an acetylcholine rich environment at the NMJ. Examples of such pharmaceuticals are: neostigmine, pyridostigmine, potassium chloride and DMSO. All are impractical for treating a large animal such as a horse. Both neostigmine and pyridostigmine, agents of transient action, have some limited value for example, when a blacksmith appointment is looming and the horse needs to be symptom free for a specific window of time on a specific day. In this case a dose of 1800 milligrams pyridostigmine orally in the morning feed (using 60 milligram tablets) followed by a dose of 10 milligrams neostigmine intramuscularly no less than three hours prior to the appointment helps the horse dramatically (as well as all concerned) but this approach is temporary and requires coordination and timing.

The medical community agrees that MG frequently starts during or after a prolonged period of intense stress, for example, emotional stress, malnutrition, chemical exposure, food sensitivity and so on. When prisoners of war in Singapore during World War II developed MG malnutrition was suspected. After introducing a vitamin rich diet, these patients were restored to more or less permanent remission. Following the war Europe experienced a virtual epidemic of MG. When a highly nutritious diet was used, similar improvement was reported. Nutrients generally accepted as stress-protective include all the B vitamins, magnesium, manganese, copper, zinc, and vitamins C and E. They are some of the many vitamins and minerals involved in energy production and neurotransmitter production.

Vitamin B1 alone is exceedingly useful it is key for acetylcholine synthesis, it helps acetylcholine bind to receptors and it enhances the effects of acetylcholine. Vitamin B2 plays a role in tissue respiration. Vitamin B3 helps nerve cells make serotonin, an important neurotransmitter. Vitamin B6 also plays an essential part in neurotransmitter synthesis. Vitamin B12 is a requirement for the synthesis of choline, a building block for acetylcholine. Magnesium activates many enzymes it is energizing at moderate levels but at higher levels it acts as a muscle relaxant. Manganese has a role in acetylcholine synthesis. Copper is interesting in that women require more than men many horse owners believe mares require more copper than geldings and stallions. Zinc reinforces the immune system. Vitamin C alone has as much if not more value than vitamin B1 in addition to promoting healthy muscle contraction and metabolism and helping with neurotransmitter synthesis, it has (drum roll please) mild anticholinesterase activity. A deficiency in Vitamin E, important in energy metabolism in muscles, leads to elevated muscle protein breakdown as in MG. According to several published reports, human MG patients have been successfully treated with megadoses of vitamins B1, C and E.

As of the 1930’s some doctors were prescribing vitamin supplements in megadoses in 1967 the term Orthomolecular Medicine was contributed by Linus Pauling in order to convey the concept “the right molecules in the right amounts”. One of the early originators of Orthomolecular Medicine was a 1936 graduate of Duke University School of Medicine, Frederic Klenner. Using vitamin C in conjunction with other nutrients to fight a number of illnesses, among them MG, he was influenced by earlier work that linked nerve degeneration with multiple nutritional deficiencies. Eventually he developed a protocol for MG (and multiple sclerosis), described in his paper, “Response of Peripheral and Central Nerve Pathology to Mega-Doses of the Vitamin B- Complex and Other Metabolites”. This same protocol can be extrapolated for use in horses with extraordinary positive results. For the average one thousand pound post-synaptic myasthenic horse on a healthy diet the following nutrients can be added to the total daily ration:
10,000 IU Vitamin E
24 grams Vitamin B1
2 grams Vitamin B2
1.5 grams Vitamin B3
9 grams Vitamin B6
175 grams Vitamin C
50 grams Choline
3 grams Magnesium
300 milligrams Zinc

Additionally, 10,000 micrograms (mcg) Vitamin B12 (for example 2cc of 5,000mcg/cc B12) can be given intramuscularly 2 to 3 times weekly. Loose manure from megadoses of Vitamin C is not a problem because MG horses have a tendency toward constipation to start with and Ascorbic Acid with wild Rose Hips (rich in bio-flavonoids) can be fed using time release 1500 milligram tablets blended into hay cubes pre-soaked in water. Injectable vitamins are impractical on a daily basis and come with the added unnecessary risk of allergic reactions (anaphylactic shock).

In conjunction with megavitamin therapy, there are a variety of herbs suitable for use in horses with MG that are useful for restoring and maintaining a healthy immune system. For restoration the combination known as Essiac Blend can be top dressed on the grain or added to soaked fiber (beet pulp, hay cubes, hay pellets, hay stretcher, wheat bran, etc.). It is comprised of Burdock (a strong liver purifying and hormone balancing herb), Sheep Sorrel (a diuretic), Slippery Elm (for all inflamed surfaces), Rhubarb Root (a mild laxative), and Talisman. For immune system maintenance in a horse with MG, all of the following are of benefit: Horseradish Root powder, Broccoli powder, Parsley Leaf powder, Red Clover blossoms powder, Wheat Grass powder, Cat’s Claw and Astragalus. Astragalus is an adaptogen it is respected as probably the most important of all herbal deep immune tonics.

The MG horse will fare better if the caretaker remembers that MG has a tendency to reappear in stressful situations, especially if the diet is unsuitable. Usually the condition gets worse as the day progresses. Any planned activity that amounts to a stress should be scheduled early in the day, such as transport, shoeing or trimming. Denial of pasture access and heavy exercise are both known to drop the bottom out of even a healthy horse’s circulating vitamin C levels. Aside from the main objective of stress reduction, pro-active immune support is helpful one option is once a month dosing with Colloidal Silver (60 milliliters of a 500 parts per million colloidal suspension orally or intravenously). All vaccination and deworming programs should be re- examined. Research has shown that even routine vaccination exacerbates active MG in other species. Repetitive vaccination amounts to an immunologic challenge to the horse’s already compromised system. Many over the counter deworming products contain ivermectin, a GABA (inhibitory neurotransmitter) agonist. Antibiotics belonging to the class Aminoglycosides are likely to cause problems if used systemically, as they can cause neuromuscular blockade examples from this group are Gentamycin, Tobramycin, Amikacin, Kanamycin, Streptomycin and Neomycin. Slightly less risky are the Quinolone antibiotics (Ciprofloxacin), the Macrolide antibiotics (Erythromycin, Azithromycin) and the Tetracyclines. Immunosuppressive steroids should be reserved for those horses that have lived with Shivers for years they have a place in critical situations but should be set aside once the patient is stabilized and made reasonably comfortable.

The Lambert-Eaton Myasthenic Syndrome (LEMS) Horse

With an understanding of Shivers as a problem of neurotransmission at the NMJ it becomes possible to differentiate a second clinical entity that could be called the ‘pre-synaptic myasthenic horse’. When release of the neurotransmitter acetylcholine from the nerve endings into the synaptic gap is reduced due to antibodies against a membrane protein of those nerve cells (the active zone of the pre-synaptic membrane), the consequence is interruption of neurotransmission and eventually the typical myasthenic syndrome. In MG the autoimmune process happens at the post-synaptic location, at the acetylcholine receptor sites of the muscle cells. When the autoimmune process takes place at the pre-synaptic nerve terminal the disorder is labeled (in humans) Lambert-Eaton Myasthenic Syndrome (LEMS). Interestingly the affected human body parts are primarily the proximal muscles of the lower limbs (thigh and pelvis) resulting in an abnormal gait. Most patients are between 50 and 70 years old LEMS is twice as common in men as in women, the same ratio found in horses with Shivers. A striking component of LEMS is ‘anti-cholinergic syndrome’. The LEMS horse likewise displays a multitude of symptoms that would be expected in the presence of acetylcholine insufficiency. Whether the absolute quantity of acetylcholine is sufficient or not should not hinder our comprehension of what the outside of the horse is telling us. A thorough assessment for clues will enable the observer to correctly conclude whether a Shivers horse is pre-synaptic or post- synaptic. (The post-synaptic horse is generally quite normal except for hind leg muscle cramping.)

In light of current research on LEMS in humans, the specific findings in a ‘pre-synaptic myasthenic horse’ are exactly as one might expect: any and all parts of the autonomic nervous system are dysfunctional to one degree or another. Those bodily functions that happen automatically in a normal horse are now deficient. Everyday caretakers have the responsibility of noticing all these peculiarities which veterinarians can easily miss. Even if everyone else misses the diagnosis, the blacksmith will recognize the horse’s primary discomfort when attempting to trim one or both hind feet. Over a long period (years) the horse will eventually demonstrate categorically that he has a number of other symptoms. The pre-synaptic horse prefers to dunk his grain and/or hay in a water bucket. Why? Because he has a dry mouth (inadequate salivation). Naturally he has a predilection for choking on dry foodstuffs. He tends to take a long time to eat for the same reason. His eyes are also dry due to reduced lacrimation (tear fluid production). His manure piles are scant. Why? He is chronically constipated. He periodically hyperventilates at rest, suggestive of a Chronic Obstructive Pulmonary Disease (COPD) horse. Why? He has pulmonary muscle fatigue which contributes to patchy sweating. He has a shortened stride going up and/or down hills. Why? Overall muscle tone is weak, especially in the hind legs. Delayed tendon reflexes ultimately lead to marked distension of the flexor tendon sheaths above the hind fetlocks. Even the muscles of the upper eyelids might be drooping. Dehydration should be monitored when the horse experiences excessive sweating at rest a hot humid day can trigger excessive stress for a body already at war with itself. The history might include food allergies and ‘sweet itch’ dermatitis in summer different autoimmune problems tend to cluster.

One wonders what goes on at the cellular level to initiate such a host of LEMS-like issues in these horses. The primary disorder in LEMS is reduced release of acetylcholine from the nerve endings into the synaptic gap. The body makes antibodies against a membrane protein of the nerve cells this type of membrane (the voltage gated calcium channel) is affected by several classes of neurotransmitters called neuromodulators. Neuromodulation is a relatively new concept. It can be thought of as ‘neurotransmitters on assignment’, floating around in the cerebrospinal fluid, influencing (modulating) the overall activity of the brain. Some neurotransmitters are considered to be neuromodulators, for example, serotonin and histamine. Serotonin is famous for promoting feelings of well-being. It is found predominantly in the intestinal tract of humans and animals. A smaller amount that is synthesized in the central nervous system has various functions: regulation of mood, appetite, sleep, muscle contraction, memory and learning. In humans stress in the form of poor diet and/or lack of sleep ultimately leads to serotonin deficiency (along with clinical depression according to most researchers). Nutrients that foster serotonin synthesis and thereby plug the drain are: vitamins B3, B6, C and E, biotin, folic acid, methionine, copper, iron, magnesium, manganese and zinc. These nutrients can be termed serotonin boosters certainly most of them also have value as anti-stress nutrients. An amplified potential for positive changes that can be jump started by using certain nutrients in certain amounts and ratios (and in the same respect by using megavitamin therapy) is implied by the concept of neuromodulation.

Approximately two-thirds of all Shivers horses are male. Male horses have the sex hormone testosterone. Testosterone antagonizes serotonin. Female horses have the sex hormones estrogen and progesterone. Progesterone is the best friend serotonin ever had it is a selective re-uptake inhibitor and an inhibitor of serotonin breakdown all in one. Perhaps female horses have a built-in protection mechanism against developing Shivers in the form of their circulating estrogen and progesterone levels. In fact, progesterone DOES have a well documented neuroprotective effect, so much so that it is given to humans with massive brain trauma in those cases so extreme that no other options are viable. The pre-synaptic Shivers horse can use all the neuroprotection it can get. (The problem is on the nerve cell side of the NMJ which is taking orders from the central nervous system which ultimately involves the brain.) Oral supplementation with a 0.22% solution of synthetic progesterone , at a dose of 0.02 milligrams per pound of body weight once daily will dramatically reverse all the symptoms displayed by a pre- synaptic Shivers horse (of either sex) within 2 to 3 days. How is this possible? Progesterone boosts serotonin levels which does much more than just make the horse feel peaceful. Among other things, serotonin has a direct effect on muscle contraction, it modulates skeletal muscle oxygenation and it plays a role in sleep cycles. (Typically myasthenic syndromes get worse as the day goes along). But most impressively serotonin acts as a neuromodulator. Neuromodulators by definition influence both the release of neurotransmitter from the pre-synaptic nerve cell and the post-synaptic cell’s response to the neurotransmitter, altering in a complementary way both the input and the input-output relationship.

Over the last several decades it has become acceptable veterinary practice to provide different preparations of estrogen and/or progesterone to horses of both sexes for purposes ranging from mood alteration (the lunatic stallion or the grumpy mare) to helping maintain muscle tone (‘loose stifles’, weak back muscles) to attention deficit. (More conservative over the counter oral supplements promoted as ‘calming’ usually contain some combination of magnesium, vitamin B1, tryptophan (a precursor of serotonin) and a wide range of herbs: chaste berry (vitex), skullcap, chamomile, vervain, milk thistle, meadowsweet, passion flower or raspberry leaf.) How can administration of a hormone, progesterone, by boosting serotonin, a neurotransmitter, not just make a moody horse feel better but thoroughly over-ride anti-cholinergic syndrome in the pre- synaptic Shivers horse? Serotonin must be operating in the role of neuromodulator. This premise can be substantiated when the hormone progesterone (with its ascribed inherent capacity for neuroprotection) is eliminated from the treatment plan completely. By substituting a combination of all serotonin’s next best friends into the same pre-synaptic Shivers horse the same all encompassing improvement is achieved. As expected, by virtue of the fact that they are friends as opposed to best friends they take an extra day or two to get the job done. Appropriate daily supplementation for a one thousand pound pre-synaptic horse would be the following serotonin boosters:
20 grams tryptophan
1500 milligrams vitamin B3
600 milligrams vitamin B6
12 milligrams folic acid
3 grams methionine
1 gram magnesium
6 grams vitamin C
65 milligrams copper
275 milligrams zinc
250 milligrams manganese
4000 IU vitamin E
balanced with vitamin B1 (2 grams), vitamin B2 (500 milligrams) and choline (2 grams) along with serotonin allies chromium (2 milligrams) and Ginko Biloba (500 milligrams). This formula works quickly (within 3 to 4 days) and efficiently for the pre-synaptic horse. It produces mild to moderate improvement in the post-synaptic horse.

For the pre-synaptic Shivers horse supplementation with serotonin boosters amounts to a fairly sophisticated yet simple to administer horse friendly approach. Unfortunately for the patient those bothersome in-laws, the autoantibodies, are not leaving anytime soon. Immunosuppressive drugs like steroids and azathioprine can force their eviction within about six weeks but the total body will suffer collateral damage in the interim. A better treatment approach could be more accurately thought of as ‘enhanced neuromodulation’. Mechanisms for healing already contained within the system are maximized while simultaneously a healthier immune system is enabled and enhanced. Long term considerations might include herbal additives and joint supplements. Of all the herbs that are used for mood disorders in horses, chaste berry (also known as vitex) is arguably the most useful it balances estrogen and progesterone in females and counteracts testosterone (not a friend of serotonin) in males. It is thought to have the added benefit of delaying the onset of Cushing’s syndrome, another stress related scenario, in older horses. Oral or injectable glucosamine is a good pain relief strategy for the post-synaptic horse that competes on a regular basis as well as for the average pre-synaptic horse. Without question the most helpful management practice for any Shivers horse is 24 hour turn-out, with constant grazing available. For horses and humans alike exposure to sunlight is a requirement of serotonin. Humans are not the only species to suffer from seasonal affective disorder (SAD).

The Fibromyalgia Syndrome (FMS) Horse

Fibromyalgia in horses is in most instances a diagnosis by exclusion. The afflicted horse is not ‘right’, nothing has been found to improve the horse, and specific symptoms are easily mistaken for behavioral bad habits. A thorough history becomes particularly useful ideally when it covers a span of years. Watching a FMS horse deteriorate is like watching grass grow. In almost every case there is an account of some (often forgotten) traumatic emotional or physical event prior to the onset of symptoms. The classic example is the gelding that had a ‘difficult castration’. Performance horses that spend much of their lives in transit or in dusty stalls are prime candidates. Many times the history includes an episode of prolonged treatment with antibiotics and/or steroids the one infectious scenario that is not usually considered or easily documented but is almost always present is an underlying chronic systemic low-grade fungal infection. Fungal infections in horses can be external, internal or both, acute or chronic, and more frequent at certain times of the year, typically late summer and fall. In every case they are opportunistic by nature like rare orchids that require certain growing conditions, they thrive in environments characterized by darkness, dampness, warm temperatures and low oxygen. Examples of the many acute (sudden onset) fungal diseases occasionally seen in horses are moldy corn poisoning, Australian stringhalt, fescue toxicity and certain foal pneumonias. In cases of chronic (slow onset) fungal disease, when the possibility of a fungal component is targeted and appropriate measures are instituted, the bulk of the FMS horse’s problems melt away within a few weeks. These problems fall into five general categories: cranial nerve deficits, microcirculatory deficits, generalized chronic fatigue, endocrine imbalances and immune mediated sequelae. Due to the common denominator of stress, a complex immune mediated cascade of events can set the stage for a specific autoimmune problem like Shivers to eventually make its appearance.

Typical of ‘flight or fright’ animals, horses react to stress with a natural reflex posture that can be seen from afar. They switch from the relaxed back, head down grazing stance to a hollow backed high headed one. Wild horses, dependent on their ability to forage steadily and still get moving quickly, alternate between these two frames continuously. Domestic horses that are healthy and stress free have little need for the flight stance. Nevertheless, they respond to stress in the same predictable manner. Just look at a horse while racing, walking on sharp rocks or responding to a drastic change in environment. Horses with FMS are perpetually hollow through their toplines they can no longer carry any muscle mass over their backs due to skeletal muscle deconditioning. Similarly, deconditioning of pulmonary (lung) muscle amounts to loss of compliance (ability to expand and contract) at the level of the alveoli, where oxygen exchange occurs, producing bouts of asthma or COPD (heaves). Breathing becomes hard work. Cardiac muscle weakness leads to mitral valve prolapse in humans and to aortic regurgitation in horses, i.e., a loud diastolic murmur with or without left ventricular enlargement. Chronic fatigue quite naturally ensues.

Horses with FMS seldom have dapples (branches of the capillary tree of arterial oxygen rich blood supply) because they have microcirculation deficits and poor oxygenation of tissues farthest from the heart. Low oxygen levels in the feet can result in persistent thrush around the frog, white line disease and poor quality hoof growth. Total body soreness might include the soles of the feet and hypersensitivity to touch (grooming tools, insects) anywhere on the upper body. Myofacial pain will be manifested according to which cranial nerves are involved. TMJ (temporomandibular joint) and masseter muscle (facial nerve) pain can turn eating into a long distance marathon. Hypersensitivity to certain wavelengths of light (optic nerve neuritis) or sound (auditory nerve neuritis) can result in head shaking or explosive behavior. Loss of equilibrium (vestibular nerve neuritis) eventually leads to stumbling, falling down, problems moving on uneven ground and problems standing up in a moving horse trailer. Not surprisingly some individuals start cribbing (a compulsive habit which affords the horse some relief in the form of endorphin release).

To say that hormones and neurotransmitters enjoy a close relationship is a gross understatement the details of their interactions are varied and complex. Reflecting different endocrine imbalances, FMS horses can exhibit extremely high or low estrogen, progesterone or testosterone levels, excessive sweating or anhidrosis, and/or insomnia: sleep disturbances which contribute to chronic fatigue. Chronic depression, mood swings or sudden kicking episodes which have a biochemical basis will slowly escalate. Horses that display a shifting leg lameness (lame in one leg this week and lame in a different leg next week) from front to back and/or from side to side are nearly always FMS horses. Small animal veterinarians dealing with a shifting leg lameness will quickly suspect underlying infection equine veterinarians are cautiously reluctant in this regard. (Immune mediated disorders are more commonly diagnosed and treated in small animals than in horses.)

Immune mediated neuritis in the FMS horse manifests most dramatically in the head area (cranial nerve involvement) and the hind legs (stringhalt, another hind leg lameness). Stringhalt is defined as intermittent upward fixation of the patella and usually has its origins in trauma to the nerves supplying the lower cervical and upper thoracic portion of the horse’s nervous system. It can be observed at any of the forward gaits and is much more common in FMS than Shivers. By the time either condition appears veterinary intervention is critical. The following protocol is user friendly, horse friendly and effective: a double dose of fenbendazole daily (4.6 milligrams per pound) for 5 consecutive days followed by a once daily dose of ketoconazole tablets in the feed (2 milligrams per pound) for 15 days. Ketoconazole, a 200 milligram time release tablet, is quite palatable and can be added directly to the grain without any extra steps for the caretaker. Fenbendazole in this instance is used to rejuvenate the lining of the gastrointestinal tract. It strips off the top layer of non-functioning cells in the large intestine, it has an escharotic (drying) effect on any ulcers, it elevates the white blood cell count, it stimulates the immune system and it kills off any overgrowth of Candida in the lower gut. Conveniently it also deworms the horse simultaneously. Ketoconazole kills most garden variety fungal species so efficiently that an ultra conservative dose is sufficient. It has the added beneficial side effect of lowering the horse’s serum cortisol, the stress hormone associated with Cushing’s syndrome. With serum cortisol back within normal levels healing can proceed naturally and unimpeded. Stringhalt in these horses will gradually resolve but a follow-up treatment regimen of the appropriate nutrients in the right amounts will be necessary for the FMS horse displaying Shivers.

All the same aforementioned long term goals of stress reduction and stress management apply to the MG horse, the LEMS horse and the FMS horse. Shivers can be effectively handled with common sense nutritional support, custom tailored to the particular myasthenic syndrome at hand, either pre-synaptic or post-synaptic. Once the immune system is returned to a normal state of affairs, it is important to appreciate the potential for relapse if care is not taken to safeguard the horse’s health. In the particular case of a draft horse or draft horse cross, a genetic pre-disposition to developing Shivers cannot be ruled out. Consequently it behooves any prospective new owner to question the breeder about the occurrence of Shivers in any known family members as part of the preliminary information gathering process. Any consulting veterinarians might be asked to contribute their personal opinions about the subject horse’s ability to back up and move the hindquarters over while standing quietly this exercise is easily incorporated into the standard pre-purchase evaluation for overall soundness.

This work honors those teachers who have gone before us and continue to light the way: Joseph Haines, DVM, Frederick Klenner, MD, Frank Palka, DVM, Walter Pruitt, Ray LeRoy & the horses Piedmont Pete, Brave Illusion and Percy Vere.


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