We have had IMM listed in our list of Genetic Issues under "Other Genetic Issues" for a while now but thought since the recent release of a readily available "For Purchase" test has brought a lot more notice to this disease we would publish an article on it.
Have you ever had a horse that lost a drastic amount of weight in a very short time? Was it just after you vaccinated it or it came down with Strangles? Good chance the horse had a mutated gene which caused that issue.
IMM stands for Immune-mediated myositis - it is a dominant disease and you can have a genetic test done on your horse to see if it carries a copy of the mutated gene. Even though it is dominant (meaning it only needs one copy to show symptoms) many horses that have this mutation never show any signs. That is because it seems to need a trigger. Right now known triggers are Strangles and certain vaccines.
An IMM horse having an attack will rapidly lose muscle along the backbone - to the pont where you can see the skeleton. This happens within 2 days to 2 weeks, It is treatable with Corticosteroids - and should be treated ASAP. Once treated, horses can usually come back to their original weight within a few months.
So far, the IMM MYH1-E321G variant has only been found in Quarter Horses, but it seem to be fairly widespread in the cutting and reining lines.
IF you own a horse that fits the description above (rapid muscle loss after an infection or vaccination, especially over the back and hind end muscles) seek help from a veterinarian.
Our Previous Policy was to not publish any PSSM positive horses younger than 20 years of age unless we had the owners permission - this has changed.
As of April 1st, 2019 we are transitioning into Publishing all PSSM results on all Quarter horses in the Members online database as AQHA has now made those results accessible to the public anyway. We will also be publishing all PSSM 2 results that are on the equiseq website under public horses. Our Policy does remain the same that if you do not want your horses information in the Members online database you just need to send us a polite message requesting your results remain private. Since the inception of our database we have been dealt with the issue of trying to make sure no horses were published that the owners wanted to remain private but in doing so there are thousands of horses that the owners really dont care if their info is published, we just cant contact everyone. So in light of the fact that the information is available anyway we will now be releasing many more horses into the online database. Again, if you do not want your horse there, just let us know. All previous horses who's owners have requested privacy for will not be released.
With the info readily available from AQHA we now have a lot more 5 panel stats on a lot more stallions in the database making it easier to try to track where PSSM has come from on horses who were never tested, and also making it easier for those who want to use nn stallions to check their status.
I purchased Starbucks (Ima Mocha Chip) a little over a year ago. I was wanting a horse that I could use myself, but eventually my granddaughters would show at 4H. I paid to have a vet check and the vet checked everything out and ran some blood and it came back with what I think was elevated proteins levels. she took another test and while we were waiting for the results I went ahead and purchased my dream horse.
When the test came back the results where more in a normal range. About 8 months after buying her, my daughter was at the trainers with her, when after about a 15 minute warm up she started sweating horribly and couldn't engage her back end and she was stumbling everywhere. She had an elevated temp and the vet was called. She could not move. She had tied up.
The vet suspected PSSM and tests came back positive for PSSM 1. We have not ridden her since. We have changed her diet, replaced alfalfa with grass hay, she is on cool pac, and vit e and in a dry lot. We are just starting her back with walking but we are scared to ever take her to a show or use her how we intended and will never have any beautiful babies.
We are heart broken and scared to use her....