Equine exertional rhabdomyolysis
Equine exertional rhabdomyolysis (ER) is a syndrome that affects the skeletal muscles within a horse.
Depending on the severity, there are various types of ER, including sporadic (i.e., Tying-Up, Monday Morning Sickness/Disease, Azoturia) and chronic (i.e., Polysaccharide Storage Myopathy (PSSM) and Recurrent Exertional Rhabdomyolysis (RER)).
[1] Equine Exertional Rhabdomyolysis (ER) is a general term used to define both sporadic - (infrequent) and chronic - (repeated) manifestations of the condition.
[1] The types of equine ER that are considered sporadic include tying-up, also commonly referred to as Monday morning sickness and/or Monday morning disease, and azoturia also known as black water disease, set fast, and/or paralytic myoglobinuria.
[1] Tying-up related is mild as compared to azoturia, which is the more severe case of sporadic ER.
[1] Sporadic equine exertional rhabdomyolysis (ER) can be found in any horse regardless of breed, age, or gender.
[1] Polysaccharide Storage Myopathy (PSSM) is commonly found in calm muscular breeds such as quarter horses, and Belgian drafts.
[1] Recurrent Exertional Rhabdomyolysis (RER) is commonly found in breeds that are high strung such as Arabians and thoroughbreds.
On days the animal is not being ridden or working, if the horse ingests feed packed with simple carbohydrates, this can cause too much energy in the form of glucose to be created.
[1] The excess glycogen within the muscle cells that lack oxygen begin to function anaerobically to produce the needed Adenosine Triphosphate.
The cell membranes may then be damaged if the horse is forced to continue work, which allows muscle enzymes and myoglobin to leak into the bloodstream.
However, if excessive rest is also allowed, this can be cause for an even greater probability that PSSM ER could develop.
[1] Regarding Recurrent Exertional Rhabdomyolysis (RER) it is muscular contractions that can lead to this type of ER.
For example, if a horse were to ingest the blister beetles and/or Day Blooming Jasmine - a broadleaf evergreen shrub,[3] each can cause signs of ER.
Ingesting ionophores toxins, such as those found in day blooming jasmine, can cause the heart muscle to become inflamed, which can bring about signs of ER.
[1] Signs for both sporadic and chronic ER can include a reluctance to move, stiffness or shortened gait when the animal is forced to move typically found in the hind legs, and muscle spasms or cramps, with hard, painful muscles (especially the hindquarters) when palpated.
[4][1] If an observer is unfamiliar with ER, initial symptoms may appear to be tiredness or perhaps lameness, but the condition is far more complex.
[1] Signs of a severe bout of Sporadic or Chronic ER may include reluctance to move, lying down and refusal to rise, remaining in a singular stance such as sit, and can develop lameness permanently due to muscle deterioration.
[1] For mild or moderate cases a vet may recommend or prescribe a Nonsteroidal anti-inflammatory drug (NSAID).
[1] For bouts of Sporadic ER, a horse can be turned out to pasture after allowing for a few days of rest and continued use of prescribed medications should there be any.
[1][6] Changing diet regime to a high-fat low-starch can be beneficial for the horse, as it can help with excitement.
Blood tests such as Creatine Kinase Concentration (CK), Aspartate Transaminase Levels (AST), and/or Lactate Dehydrogenase (LDH) should be normal before the horse is returned to work.
Grain may need to be cut in half and feed ration should also be downsized prior to rest days.
Ensure that the horse is cared for, for an issues to the immune system and allowed to recover before continuing training.
Adding potassium and salt to the diet may be beneficial to horses that suffer from recurrent bouts of ER both chronic and sporadic.
