Fibromyalgia cases trickling into practice

In every practice, there are baffling cases that defy a traditional diagnostic approach.

Nonspecific lameness concomitant with behavioral problems or a drastic change in demeanor can be difficult to explain. Practitioners may find it necessary to think outside the box in order to advance an etiology or pathogenesis.

Tough customer

By process of exclusion, one may be able to uncover a clinical picture that slips past even today's sophisticated diagnostic techniques. Equine fibromyalgia syndrome (EFMS) is one of these diagnostic challenges.

According to the American College of Rheumatology, up to 6 million Americans suffer from fibromyalgia syndrome, yet there are no diagnostic tests to confirm its existence. In humans, symptoms can include muscle aches, painful tendons and ligaments, gastrointestinal discomfort, headaches, sleep disturbances and fatigue. Theories about the cause or causes range from trauma to an infectious agent to central nervous system injury to alterations in muscle metabolism.

Diagnosing equine fibromyalgia syndrome

Symptoms

EFMS horses might exhibit autoimmune problems, micro-circulatory deficits, cranial nerve problems, endocrine imbalances, generalized chronic fatigue or a combination of these conditions. An important fact is that an individual horse or human can have two or three symptoms or as many as 20.

While most aspects of human fibromyalgia syndrome and EFMS are identical, the equine athlete will demonstrate more extreme symptoms when an already compromised immune system is stressed during work. Interestingly, in both human and equine syndromes, a fungal component exists either as a sequela or as a cause of the disease.

Clues to consider

Autoimmune problems run the gamut from immune-mediated arthritis to toxicity to immune-mediated neuritis.

Often, previously injured joints will be most significantly affected, although the horse may exhibit signs of overall body soreness. Any transient lameness that shifts from fore legs to hind legs or from side to side should be suspect.

Immune-mediated neuritis can manifest itself as stringhalt or shivers or both (analogous to human restless leg syndrome.) Chronic obstructive pulmonary disease (COPD) can be a component of the autoimmune response, often accompanied by parotid salivary gland enlargement (swollen glands), an occasional mucous nasal discharge, a non-productive cough, or a combination of these symptoms. The owner may report seasonal respiratory allergies that come and go.

Deficits in micro-circulation can lead to a multitude of problems, such as muscle deconditioning, hoof problems and skin infections. The racehorse with advanced EFMS and compromised alveolar function might exhibit exercise-induced pulmonary hemorrhage. Those individuals already hypersensitive to molds and fungi are prime candidates for developing asthma and COPD. Smooth muscle deconditioning can cause irritable bowel syndrome, leaky bowel syndrome, and their obvious sequelae (colitis and colic).

The most common cardiac muscle deficiency in humans is mitral valve prolapse; horses will sometimes develop a loud diastolic murmur with or without left ventricular enlargement. Hoof problems to consider are white line disease, chronic abscesses, petechial redness in white hoof walls, cracked insensitive laminae, and extreme sensitivity to hard ground. Poor tissue oxygenation and outward signs of toxicity go hand in hand: abnormal fat deposits at the base of the tail, a potbellied appearance, a dull greasy hair coat, and chronic fungal skin infections.

Many symptoms involving the cranial nerves get evaluated out of context and, hence, are never effectively treated. Hypersensitivity to touch (for example, bridles, insects, grooming tools, shampoos, fly sprays) can result in chronic head shyness. Add to this a hypersensitivity to non-contact stimuli (sound, light), and the stage is set for creating a head-shaker.

Facial red flag

Any suggestion of facial neuritis should be a significant red flag. Horses have the unique ability to use cribbing as a mechanism for endorphin release and the resulting myofacial pain relief. Evidence of anterior pituitary involvement is abundant. Examples are extremely high or low estrogen, progesterone, or testosterone levels; excessive sweating; anhidrosis, adrenal exhaustion syndrome; chronic fatigue; and loss of equilibrium. Stumbling, falling down, difficulty picking up or switching leads at the canter, tentative gaits over uneven or sloping ground, or difficulty standing still for the blacksmith are common complaints. The owner might notice the horse struggling to walk up or down the horse trailer ramp.

Pathogenesis

A common characteristic of both EFMS and human fibromyalgia syndrome is an accounting of one or more events prior to the onset of symptoms that resulted in serious trauma that is physical, psychological or both. One theory is that the immune system is overtaxed to such an extent that fungal elements are able to gain a foothold somewhere in the body. For this reason, taking a thorough history is of paramount importance.

An investigative conversation with the horse's most recent long-term caretaker is time well spent. Whether an unidentified fungus is a primary pathogen or a secondary invader becomes a moot point as time goes by. Continuous, insidious growth starts to wreak havoc on multiple systems' physiology. Attempts at culturing fungal elements from blood or other tissues are time consuming and frustrating at best.

Amelioration

Most, if not all, of the problems associated with EFMS can be significantly ameliorated with daily oral dosing of a fungicidal drug for a minimum of 14 days. Some individuals benefit from a longer course of treatment (up to 12 weeks). In a two-week treatment program involving 20 symptomatic horses, all improved either 100 percent or nearly 100 percent.

A complete history suggestive of EFMS, coupled with dramatic improvement post treatment (a calmer, relaxed, yet attentive horse,) supports the diagnosis. Additional suggestions to the client should include: elimination of molasses and refined sugars from the diet; feeding a concentrate that provides adequate protein, complex carbohydrates, and fat; and avoidance of prolonged antibiotic, steroid and hormone therapy.

Dr. Bishop, a 1976 graduate of the University of Pennsylvania School of Veterinary Medicine, operates a private practice in rural North Carolina. For more information on EFMS, contact Dr. Bishop at Sport Horse Associates, 1404 McCaskill Road, Carthage, NC 28327; e-mail sporthorse@carolina.net; telephone (910) 949-3878.