AERC Dr. Jeannette Mero on Tying UP Part 2

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Tying Up—Unraveling some of the mysteries surrounding this syndrome. Dr. Jeannette (Jay) Mero, DVM, AERC # 15049, 2,560 sanctioned endurance miles, (yes, I looked her up), Chair of the AERC Veterinary Committee, has her own veterinary clinic @ and in searching for contact for her I also found this: DSLD research

Best to read Part 1 first, but, I brought forward the different categories of Exertional Rhabdomyelosis from Part 1:
There is Extrinsic ER ( Exertional Rhabdomyelosis) and Intrinsic ER; Extrinsic means likely we can cause it and manage it; the causes and solutions are under our control. Intrinsic ER means that the causes are not under our control but we MAY be able manage it.

Extrinsic ER: under this heading is something vets call *Sporadic ER*— the horse gets it sporadically or intermittently

Intrinsic ER: under this heading are the genetic causes: Recurrent ER, Malignant Hyperthermia, Idiopathic causes (meaning we don’t know the cause) and a Chronic ER — under Chronic ER the causes are PSSM1 and PSSM2.
In case you want to know: PSSM stands for Polysaccharide Storage Myopathy. And PSSM 1 and 2 refer to inherited dominant genes for this syndrome. Here are some FAQ’s to refer to about the PSSM.

So, if a horse with Sporadic ER starts presenting with it more times despite good management, the category is changed and those horses now have Recurrent ER which likely has a genetic component.
This genetic component is a gene mutation that has been found in TB’s, Standardbreds, and Warmbloods and is suspected in Arabians (although in Arabs the genetic component is now suspected to be different/ perhaps a combination of genetic components; hence the ongoing research on this in Arabs; especially arabs who are endurance horses.).
In horses with Recurrent ER (RER) it seems that there is/are (a) trigger(s) to the event, especially in nervous excitable animals; some event triggers the tie up. Example: the start of an endurance ride, fighting them for 10-15 miles ( Yep, that happened to me at Klickitat ride 2012!, my horse did not tie up, but his heart rate was erratic and did not pulse down in 10 min! He usually drops down very quickly, but then we fought….. arghh!
The event that happens inside the muscles is something to do with Ca+2, Calcium ion, the calcium channel, the calcium ion goes in but cannot get back out.

Management of Recurrent ER entails: decreasing stress levels, maintain routines, don’t do anything out of the ordinary, the position of their stall needs to stay static, their work schedule needs to be regular, regular DAILY exercise, and low sugar, high fat diet should lead to a calmer temperament in order tl balance the Ca+2 pump in the cells.

It has been shown that an equine diet of higher calories, higher starch does lead to higher anxiety levels. 10% of the diet needs to be fat—LMF Gold, Rice Bran, and Ultium were mentioned as possible products for horse dietary issues in management of horses with RER.
Here is an excellent website for RER FAQ

One indicator of the level of and confirmation of muscle damage is CK level as a biomarker in the blood. CK-Creatine Kinase. See this website for more info

Normal CK levels are 95-565 U/L ( units per Liter). A horse with ER levels can reach 2000-200,000 U/L
Dr. Susan Garlinghouse has an article about blood panels here

1992 onward, we have known about PSSM1 or the possible existence of genetic mutation as far back as 1979, but have pinpointed the exact mutation from 1992 onward. This genetic mutation enhances storage of sugar/saccharides, glycogen, and polysaccharides in the muscle. You can see this upon differential staining of a muscle biopsy; the stained normal muscle cells are a lovely pink, but muscles with excess polysaccharide stain a bluish where the excess packets of polysaccharide are stored.

You can do and probably should do this test upon pre-purchase; Dr. Mero sounded as though this becoming a routine test. Hmmmmm, author stops, taps finger on chin… all the things I SHOULD have thought about before buying the two Arabians I have now. I have 9 pages of mistakes I wrote down so I could learn, this will be added. My veterinarian did not mention this upon prepurchase, and my vet is a stellar vet who works on performance horses (Polo ponies, Dressage and endurance horses consistently). Hmmmmmmm

The gene is called GYS1, Glycogen synthase. It is a Dominant trait, which means that if you cross a quarter horse who has it with an arab who does not the baby will have the genetic mutation. (yeah, nutshell genetics). Mostly this affects draft breeds, and has been ID’d in a large list of horses: American cream, gypsy vanner, Belgian, percheron, shire, quarter, paint, appaloosa, morgan, mustang, Rocky mt horse, TWH and mixed breeds.
The genetic test for this gene, which is the PSSM1 mutation, NOT PSSM2, make sure you tracked that…. is done by pulling mane hair, with hair bulbs (follicles attached) and sending the sample in.
Here is exactly how you do that: and the cost $65

Holy COW! Or is it Holy Arab CROSS!???? LOL! My head is getting Full, this is a lot of information but it is excellent information for us endurance riders. Especially those of us who ride crosses— Quarabs, Half arabs, etc.  raise your hand if you ride an affected breed or a cross with an affected breed…. Yeah, my hand is up, too. I ride a Half arab, his sire was Custody, a paint stallion. Dr. Mero did go on to say, thankfully, somewhat, that this PSSM1 mutation does affect pleasure riders more than endurance; BUT, there may be something else going on with our endurance horses; that we may notice a lower level of ER, our horses such as: * a bit crampy, less energy, less willing to go down the trail, a bit stiff* Pay ATTENTION, there may be some muscle damage going on that we don’t know enough about, yet ( hence research, yay for science and the scientific process). Horses with PSSM1 tend to be calm, sedate horses, halter/pleasure horses not animals involved in speed events and has not been found, yet, in racing QH lines.

She noted, also, that horses with PSSM1 may also have some insulin resistance leading to even more excess sugar storage, and that PSSM1 is the likely cause of Monday Morning disease or Holiday disease; see Part 1.
Symptoms: tucking up, stiff muscles, swearing, trembling flanks, reluctance to move forward. Chronic signs: lack of energy, poor performance, poor work ‘tude, back pain, rarely develop kidney disease.
Muscle biopsies are the best way to determine whether your horse is storing excess sugar. The cost of a muscle biopsy is $105, much more info is here

On to PSSM2: no GYS1 gene identified, no gene mutation, we have no genetic marker yet; however, a combination of genetic markers are suspected. Horses with RER, suspected of PSSM2 are not calm and sedate’ this is much more prevalent in high performance horses: Arabs, QH, TWH, STB, Morgan and WB’s.
These horses present with similar clinical signs lameness in hind, chronic poor performance, potential muscle atrophy.
If after reading everything and looking at your animal, Dr. Valberg’s lab is the only lab that is doing these tests on muscle biopsies so you can do two things with sending a muscle biopsy (have your vet do that actual biopsy, this is REALLY a DO NOT TRY THIS YOURSELF kinda thing ) you can find out if this is something your horse has and lend your horse sample to the growing body of research on this syndrome. First, though, best to submit a mane hair test to rule out PSSM1. Dr. Mero did say that she was facilitating Dr. Valbgerg’s collection of muscle biopsies of endurance horses to try to more quickly isolate the genetic component of PSSM2, so stay tuned, she will be sending out notices about that collection of samples; Stay glued to AERC website/ Endurance news publication! Nice, that, they will send a team to come GET them just like Lissa Fiedler did with her CK study…. In 2010. I doubt they will show up at rides because of the moderately invasive nature of biopsies, more likely to come to an area… idk, stay Tuned and do contact Dr. Mero for more information.

This PSSM2 syndrome is similar to Type 2 diabetes in humans. We want to have less sugar in blood stream and to encourage the horse’s muscles to burn fat for energy rather than sugar. Hmmmm, I did not know that could be done; Learning has occurred. It takes a while for muscles to become trained to do this. Thus, it sounded like this PSSM2 is controlled by diet, exercise; management is KEY here for these horses. These horses CAN be your average AERC horse, but they are not likely to be a competitor for top performances in endurance. Remove all grain and sweet feed from the horse’s diet, Balance calories first, then low starch, then add in the fat supplement 15-20% DE Fat. I did not catch what DE fat meant…. And when I type it into a search engine I get *defat*. Sorry, if someone knows, please comment…
Dr. Mero was pretty adamant about the regimen of managing these horses for successful lives; she said these horses need free movement, turn out, regular exercise, grazing muzzles if needed during the spring when grasses are full of sugar. She recommends DRY LOT in the spring.

She recommends stabilized rice bran for the fat content because of the balanced Ca and P ratio ( calcium and phosphorus). She recommended stabilized rice bran added to beet pulp but beet pulp without molasses. These horses need exercise EVERY DAY! For at least 10 minutes to maintain fitness these horses do not do well with time off; there should be NO break in training regimen for these horses. And, they may need more treatment at rides, here is why:
What is happening inside the muscle when ER is there? Muscle cells are dying and dead, and that is a DEHYDRATING event. REALLY? My brain said as well, recall, myoglobin is toxic to the kidneys so fluids and more fluids would be a good thing. What we see at a ride is on a continuum of slightly crampy to full lock and all levels in between, yes? This also happens early in a ride or late in a ride, dark urine. Whatever the level, though, EVERY time a muscle is damaged it is an insult to the kidneys and Dr. Mero said that she and her vet colleagues have statement that 20L of fluids can cure EVERYTHING . So, IV fluids immediately….. remember me, at age 17? Blue Mountain ride? We would have given Suzy Q fluids IMMEDIATELY!! But, AERC was started in 1972, and those rides were not sanctioned, yet, so we had volunteers, I doubt if there was a vet present… I don’t remember.. anyone remember? I just remember praying my darling mare was OK and would *get over it*. Now? Dr. Mero is making a strong statement about having a treatment vet there at the ride with IV fluids available to help these horses that show any kind of symptom on the continuum of ER possibility so that their bodies can be moved past the insult more swiftly. Yay, science! But, DON”T WAIT, treat your horse immediately. And get them all kinds of support: rugs, warmth, remember the Back on Track heat reflective blankies? Yep, those! as well as frog support, and attentive care of horses that are down.
Now, the next section is very important and was a steep learning curve for me. in an event of ER, Tying Up, your horse should get fluids FIRST with sedation. Recall or know that Bute and Banamine also effect kidneys AND interferes with veterinarian evaluation, so do NOT give those. Best to wait 2-3 days to give Bute or Banamine ANYHOW, due to the effects on the kidneys with dehydrated horses, which, folks are ALL of our horses, with or without signs and symptoms of ER.

Dr. Mero uses DMSO because it helps kidney perfusion, regardless of how it makes her smell… 

DO NOT WALK a horse that is showing tie up symptoms, that leads to more muscle damage. If you are on a ride and on the trail, stop, get off, tack loose, send word via other riders. ONLY walk your horse slowly IF you have to and you are by yourself and have no support. Cell Phones…. For support. TRY NOT to MOVE your horse at all.
In Summary: Exertional Rhabdomyelosis is a primary muscle disorder. Repeat episodes should be investigated (management? Genetic and management?)

If genetic, management CAN work, low sugar, high fat, and lots of exercise. Fluids treat everything
Apparently also, Joe Pagan, sp? At Kentucky Research is investigating whether there are Omega 3 and 6 issues with this disease.


Remember, I am not a veterinarian, I am rider, like you… and love my horses; this reproduction of Dr. Mero’s talk is an act of love for my horses and riding buddies all over. I do not KNOW this content, I am learning it like you; from the bottom up. You will notice that I did not address the Chronic ER under the Intrinsic label at all; I was unsure of where that fit and when a horse tips into that realm. Perhaps someone can add to this and /or please direct your questions about more about the content to Drs Mero and Valbgerg– the EXPERTS on this syndrome– and then as you learn more, share here for us all.I look forward to corrections to MY comments, and comments about this as we continue to learn.


3 responses to “AERC Dr. Jeannette Mero on Tying UP Part 2”

  1. Jessi Zirbel says :

    Ever find out what DE fat was?

  2. tchrlady says :

    Jessi Z, nope, not yet….. 🙂 hoping someone will know…:-)

  3. Sue Preston says :

    Interesting how this information is all coming together….PSSM1 with insulin resistance and the recent information on insulin resistance caused by iron overload. One could get a bit paranoid. On a lighter note..around paragraph 13…I can definitly understand why a horse with Monday Morning Sickness might by ‘swearing’!

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