Sunday, June 18, 2017

Health update

Our Old Dominion ride photo by Becky Pearman. Good thing she took the photos in the first 2 miles!!
Sunny is doing great at home, you would never know he had a problem last week. He is running around the field having fun, and we have enjoyed some light bareback riding at home.  His 1 week recheck bloodwork showed his CK value normal and his AST returning to normal as anticipated (The AST has a much longer half-life of 7-8 days in the horse, so in 1 week the value was about 50% decreased).  However his CBC, checking his white blood cell counts and red blood cell counts, showed decreases in two types of white blood cells, neutrophils and lymphocytes.  This raised a red flag in my mind for Anaplasmosis. Both Poptart (http://poptartthearabian.blogspot.com/search?q=anaplasma) and Rogan tested postive and were treated for this in 2016, so I know it is present at my home.  Anaplasma phagocytophilum is a tick borne disease that can cause a variety of symptoms including fever, lethargy, muscle stiffness, anorexia, edema, and skin hemorrhage/petechia, and low neutrophils and lymphocytes among other signs.  It is carried by Ixodes (Deer) ticks.  I also found a 2008 case-report (http://onlinelibrary.wiley.com/doi/10.1111/j.1939-1676.2008.0115.x/full) of a horse having a severe episode of tying up at the same time as an acute infection of Anaplasmosis; this association would have to be studied more to know if Anaplasma can cause tying-up or if it was just a coincidence, but it is certainly on my radar!  Anaplasmosis is typically treated with oxytetracycline or doxycycline and most horses respond well.

So, being the veterinarian that I am, who likes to have solid data, I sent out testing for Anaplasmosis, Vitamin E and Selenium blood levels, and genetic testing for type 1 PSSM (polysacchride storage myopathy) which is found in Rocky Mountain Horses.

Shockingly (LOL), I also have spent a lot of time researching PSSM and horses that have exertional rhabdomyolysis in general.  I hypothesize that "normal" horses do not have episodes of tying-up unless caused by external factors such as exhaustion, dehydration, or electrolytes abnormalities (ie potentially after 50-100 miles of riding).  Otherwise, I think research will eventually show underlying abnormalities in all other horses that have exertional rhabdomyolysis. Unfortunately medical research is not at that point yet, so many episodes are labeled idiopathic (or we don't know).  It could be genetic abnormalities as identified with PSSM or an infectious cause that may temporarily affect muscle such as with Anaplasma, or something else.  Currently, research with muscle biopsies group the causes of expertional rhabdomyolysis into different causes including PSSM 1, PSSM 2, and RER (recurrent exertional rhabdomyolysis); there is genetic testing for PSSM 1. The PSSM types are found in 20+ breeds, most commonly in QH and stock types as well as drafts and warmbloods (but also in gaited breeds). The RER types are found in thoroughbreds, arabians, and standardbreds. The underlying mechanism that causes the tying-up is different depending on the underlying abnormality.

Currently the management recommendations are similar for all types of exertional rhabdomyolysis, but essentially every horse is an individual with their particular needs and responses to different diets and exercise regimens.  Diet -- as low NSC (starch + sugar) as practical and add fat as needed for calories(the goal being 20-25% of daily calories in the form of fat).  Exercise-- every day is the best, even if it is only for 10 minutes and 24/7 pasture turnout is a must as well, which is easy as my horses live out with run-in stalls.  I can manage the diet readily enough, but the daily exercise will be tough; hopefully several times a week will suffice as it has for the last 10 years of his life before this episode.   I will admit that I started jogging with the horses on Friday as I certainly don't have time to exercise myself and Sunny after a full day of work.  And if I take Sunny, why not also take Rogan who is fat and needs exercise!  I also figured I would be more balanced with a lead rope in each hand, LOL!  I will have to get a photo next time.  They did better than expected (we only went 2 miles) and I think with a little practice I will have some reliable jogging partners, LOL!

On the diet, after obsessively researching all the locally/readily available options I have decided on Triple Crown Senior which is 11.7% NSC and 10% fat by weight. I decided to err on a lower NSC with a lower fat, rather than returning to Purina Ultium which as an NSC of 16% and fat of 12.4%; however the Ultium is still certainly a good option depending on availability and Sunny's taste preferences.  The food I was feeding, Nutrena ProForce Fiber has about a 20% NSC and 12% fat, good for most horses, but I would rather go lower on the NSC since Sunny had a tying-up episode.  I plan on feeding 3 qts (about 3 lbs) of the TC Senior, 1 qt Alfalfa pellets (about 2 lbs), 2 cups (1/2 lb) of stabilized flax, and 1 oz of California Trace Supplement am and pm.   This doesn't quite meet the 20-25% fat recommendation, but is certainly within the low NSC recommendations, and it is a big change from the Omolene 500.  I may end up reducing the alfalfa pellets and replacing with more senior to increase the portion of daily calories from fat, but I like the alfalfa pellets for the extra calcium to help buffer the stomach and hopefully reduce ulcers.  I will at least keep the alfalfa on hand for the rides!  The flax adds additional Omega-3 fatty acids and extra fat.   And, of course, I will adjust accordingly based on his current body condition score.

So that is the plan for now, and I continue to wait for test results... If he is positive for Anaplasmosis I will treat and continue to ride him lightly at home, but will hold off on heavy conditioning until after treatment.  If he is negative, then I will slowly and progressively resume conditioning in the next week or so.   For now I am thoroughly enjoying the bareback gaiting and dressage.  I love riding him bareback during our learning about gaiting, as I can really feeling his back change as he speeds up or slows down, or tenses and relaxes. The nicest gait so far is a 4-beat rhythmic gait about 5-6 mph, where his head and neck are relaxed but lifted in a natural posture and as he relaxes I can really feel his loin and back lift.   Hopefully this summer I will be able to submit a video to the Kentucky Mountain Horse Association for certification and permanent registration!



Sunday, June 11, 2017

Old Dominion 50: 3 miles and a tie-up (exertional rhabdomyolysis)

Not the ride photo I wanted!  Receiving IV fluids at the treatment area at Old Dominion Endurance Rides. 

I made my list, checked it twice and headed to the 2017 Old Dominion 50.  Sunny had new shoes, he was rested, gaining needed weight and ready-to-go.  Everything went smooth; he had his pre-ride salt, Ulcergard and bath.  After our short trailer ride to basecamp he settled in quickly, he even got to camp next to his best bud, Tivo! I let him rest instead of checking out the trail as both Sunny and I were familiar with it; instead he got a nice hand-walk around camp.  It got a little chilly overnight so I put a light sheet on him so his muscles wouldn't be cold and crampy at the early morning start.  When Graham and I woke up in the morning, Sunny was sleeping flat-out on his Hi-tie; he was well-rested for the 50 miles!  He ate and drank well overnight, and even pooped in his food-pan, LOL!  I was a few minutes behind schedule and only had a short warm-up so we were almost last out of camp and just started with an easy walk down the trail.  This was absolutely the best part- I had a happy, relaxed, free-striding, on-the-buckle walk past the start line!  We then joined my team, a group of 3 other friends and maintained an easy, smooth gait for the first mile or so.  One of my goals was to maintain Sunny's heart rate at <150 bpm for the duration of the ride to avoid anaerobic exercise and fatigue.  So when his heart rate increased with a combination of ride-start excitement, desire to move-out with his friends, and a few small hills, I slowed him down to a slower gait/walk until we could maintain <150.  Our friends went on ahead and just a few minutes later he stopped on trail.  I thought that was very odd until I saw he was waiting for Janice and Pete to catch up---a new potential best horse-friend  (or so I thought at the time).  Pete and Sunny then proceeded down the trail, but about 1/2 -mile later Sunny kept slowing down and transitioning to a walk which is pretty unusual -- he is typically pretty forward down the trail.  I dismounted to check him over and he started having full body muscle fasiculations.  His heart rate was around 60 bpm (normal for walking down the trail) and his hydration parameters looked great; he had barely broken a sweat.  Janice proceeded (after making sure we were okay and with my blessing) down the trail with Pete, and Sunny didn't event try to follow --- a very bad sign.   As we were now the last horse on trail, Duane (the OD's amazing drag-riding team leader) came up from behind.  He very nicely asked if all was okay -- I answered "NO" and my tears started flowing.  I quietly hand-walked Sunny for a few minutes to see if he would work himself out of the fasiculations and let him rest and drink in creek.  Unfortunately, he worsened and become more and more reluctant to move.  I made the call to pull and Duane radioed for a horse-ambulance to pick us up.  Thankfully we were only about 1/2 mile from Orkney Springs Rd. so Sunny didn't have to far to walk.  Duane had to pony Sunny out while I encouraged him from behind.
Love how relaxed and happy we both are walking past the start line!  Photo by Melissa Lizmi


Unfortunately, Graham was waiting to crew for me at BirdHaven and heard over the radio that I was 'off the horse' and 'on-the-pavement'; this was taken by everyone as a severe fall and my horse was being taken back because I was injured enough not to ride. In reality I had dismounted and led Sunny to the pavement for the ambulance ride home!  Graham was very relieved to find me well and hale at treatment with Sunny :)  But, for the rest of the ride I had many condolences and questions as to my well-being!

Back to Sunny - We had a quick trailer ride back to basecamp and were dropped off at the amazing treatment veterinarian, Dr. Lynne Johnson.  She took excellent care of Sunny and ran bloodwork immediately.  His CK (creatinine kinase) was about 12,000 u/L , definitely elevated but below the threshold for tying-up. Normal CK is generally <350 u/L, but clinically normal horses without can have levels over 30,000 u/L after a 100 mile endurance ride due to the time and intensity of the muscle use.  Sunny's hydration, electrolytes, and overall physical exam looked good, but he was very obviously short-striding in his left hind at this point and both tight and sore over palpation of his left hind gluteal muscles.  The initial diagnosis was a muscle cramp, but I was to watch him carefully for any changes, collect his urine and monitor for dark discoloration (a sign tying up and of the muscle damage breakdown product myoglobin passing through the kidneys), and return in a few hours for recheck bloodwork. He received banamine to make him more comfortable and we slowly returned to basecamp for an afternoon of R&R (and carefully monitoring!) instead of 50 miles.  He rested through the morning, enjoying his feed, hay, and water and had several nice and yellow urination's. He remained uncomfortable in his left hind with a shortened stride and he did progressively tighten some in his left gluteal muscles for an hour or so after returning to camp.   This was obvious on muscle palpation, the right side was relaxed and jiggly (like jello) and the left was taut, firm, and sore. By mid-afternoon he was looking much better and walking without such an obvious hitch. Graham packed us up to head home and I took Sunny back to treatment for his recheck.

Swollen left hind rump muscle 24 hours post-ride; Sunny is standing square.


Dr. Lynne Johnson took the recheck blood sample and on his exam noticed his left rump muscles were markedly more swollen than the right side.  I hadn't noticed; I had just assumed the difference was because he was resting a foot, or one hind leg was in front of the other.   She was concerned that he was tying-up rather than simply cramping. Unfortunately the recheck labs proved her suspicions correct.  His CK had elevated to HIGH, above the limits of the bloodwork machine--- definitely well-above the threshold for a tie-up; we had just taken the initial blood sample at the very beginning of the episode.   When horse's have an episode of tying up (or exertional rhabdomyolysis) the muscle is having a problem contracting normally and excessively contracts and tightens to the extent it damages and kills muscle cells. The substance myoglobin is released and filtered from the blood by the kidneys; myoglobin turns the urine a dark brown to black color. However, if enough myoglobin is released it can 'clog' the kidneys and ultimately cause kidney failure and death, in severe cases. Thankfully, most horse's seem to recover fully, especially with treatment.  Luckily, Sunny never even had dark urine and we treated with IV fluids and little vasodilator/sedative to help flush out any myoglobin and prevent damage. He is doing great at home now and right now (subject to change) I plan on rechecking his bloodwork weekly until it normalizes and slowly return him to full work, starting with easy walking for about 45 min to 1 hour later this week.

The obvious next concern is WHY?  What caused this to happen? How can I prevent it in the future? The million dollar question!!  Basically nobody knows.  Sunny is 10 years old and has never had an episode of tying-up previously. He is not a breed associated with any genetic myopathy/muscle storage disease. He did not work hard enough to have a dehydration or electrolyte induced episode. Anecdotally, there have been an increased number of tying-up episodes in our region this year. One reasonable theory from Dr. Lani is that the horses essentially have carb-overload or too high of NSC in their diet from the lush grass caused by the unusually large amounts of rain this spring.

Exertional Rhabdomyolysis, Stephanie J. Valberg, DVM, PhD, Diplomate ACVIM
AAEP Proceedings 2006

"Dietary Imbalances Episodes of ER may be triggered by diets with a high non-structural carbohydrate (NSC) content, inadequate selenium and vitamin E, or electrolyte imbalances. Serum vitamin E and either whole blood selenium concentrations or glutathioneperoxidase activity can be helpful in assessing potential deficiencies. Horses with ER are infrequently deficient in selenium; anecdotal reports suggest that, in some cases, supplementation may prevent further episodes of ER."

I believe Sunny has more than adequate selenium and vitamin E in his diet. He receives about 5.6 mg of selenium daily in his feed/supplements and receives 2400 IU Vitamin E and he is on fresh grass (which provides loads of Vitamin E and unknown, but likely very low, amounts of selenium)

Besides the potentially lush grass, I started Sunny on Omolene 500 this winter/spring to help him maintain weight.  He has been a picky eater and significantly preferred textured feed to pellets; Omolene 500 was one of the highest fat/lowest starch "sweet feeds" I could find available in my area. But when looking it up today, it has about a 32% NSC -- this definitely could be too high.  The goal for normal, but sensitive horses is < 20% and possibly much lower if you have horse that has founder, metabolic syndrome or other issues. For reference the approximate NSC of oats =  45%, corn = 65%, and beet pulp = 36%.  I actually had started the process of switching to Nutrena ProForce Fiber 2-3 weeks ago. He likes it!! The Nutrena feed is beet-pulp based and has a maximum NSC of 20% and fat of 13%.  As of now, he gets 3 lbs of the Nutrena feed + 1 1/2 lbs of alfalfa pellets, 1 oz NaCL(salt), and 2 oz of California Trace ration balancer supplement am and pm (also I am using up old rice bran, so he gets 1 cup of that am and pm as well; I might switch back to 1 cup of ground stabilized flax am and pm for the fat/Omega 3 fatty acids when I finish up the rice bran).

The other advice I received from several experienced endurance rider-veterinarians including Dr. Julie Bullock and Dr. Lani Newcomb is to make sure I exercise him lightly more frequently. I did a great job of resting him before this ride and in hindsight that was probably not the best thing to do for him. In the future I need to take him out for a short ride the day prior to rides, just enough to break a light sweat.  Ideally, I also would have him out for at least 10 minutes of exercise (trotting/gaiting on line or under saddle, running the fence if I take Rogan out of the field, etc) every day -- this is very hard in reality, but if I skip days I need to take an extra long time warm-up with easy walking.

Hopefully this never, ever happens again and the small adjustments to feeding and riding schedules will prevent another episode.  I figure I will know a lot more in 20 years-- maybe I actually will be a pretty decent endurance rider-veterinarian ---each mishap teaches me so much! I think my pull rate must equal my completion rate so far (just checked, not quite equal with 3 pulls and 5 completions)

We will forge ahead and take it easy with some fun mountain rides and a little more emphasis on relationship and dressage for the next 8 weeks until our next attempt at Ride between the Rivers in beautiful Elkins WV.