Information Resources:
Informational Links: Testing Forms:
Our Viewpoint:
Hyperkalemic Periodic Paralysis Disease (HyPP) is a dangerous genetic defect, therefore it is not included in our breeding program.
There are breeders on both ends of this debate. Some feel that all Impressive bloodlines are undesirable, and others continue breeding N/H horses for the ease of fitting them for show.
Our opinion is that with testing so readily available as well as affordable, there is no need to eliminate all of the Impressive bloodlines. We do however, feel that all horses with H/H or N/H status should be spayed or gelded to prevent this defect from passing on.
As breeders, our goal is to produce the BEST example of our chosen breed, the Appaloosa. This trait in no way reflects our goals.
The following information has compiled from sources on the web. The majority refers back to information from the site "Bringing Light to HyPP" located in the resource list at the top of this page with their permission. Please visit their site as well - they have additional information including videos of horse with HyPP complications, and a listing of know carriers. We are currently compiling a ApHC list of know carriers and we will be publishing that here as well as their listing of AQHA carries in the future. As a breeder, it is important as you research the bloodlines of the the horses you add to your herd, that you are at least informed of the status of known HyPP positive horses. It is up to you then to decided if you want to add this disease to your pasture.
What Is HYPP?
Hyperkalemic Periodic Paralysis Disease (HyPP) is a muscular disease that affects both horses and humans. It is caused by a hereditary genetic defect that disrupts a protein called a sodium ion channel, a tiny gateway in the membrane of muscle cells.
The genetic defect disrupts the channel's normal opening and closing, such that uncontrolled sodium influxes occur. These influxes in turn change the voltage current of muscle cells, causing uncontrolled muscle twitching or profound muscle weakness. High levels of potassium in the blood usually are present when the disruptions in the ion channel occur.
Symptoms can include:
Since Impressive descendants are so numerous, the genetic mutation in the bloodline is widespread effecting all breeds that accept crossouts with American Quarter Horses as well as grade horses and ponies that contain his bloodline.
HyPP is unique in that it is the first equine disease in which breeding and molecular genetics have yielded a specific genetic mutation identifiable with a named bloodline.
How do you know the HyPP status of a horse?
A DNA test now has been developed and presently is available at UC Davis to identify horses carrying the defective gene
causing HyPP. Only horse containing Impressive bloodlines currently need to be tested.
HyPP was identified in 1985, and a test was made available for public use in 1992. This blood test detects the presence or absence of the specific genetic mutation which has been found in the extended pedigree of Impressive descendants. When the test was made available to the public, breeders were encouraged to test their breeding stock and choose horses that did not carry HyPP to be used as breeding stock.
Testing forms and information can be found at the top of this page. The test simply requires a hair sample be sent in to be tested and currently cost about $50.00 for all breeds and the ApHC offers a test for Appaloosas for $35.00.
The three statuses of HyPP:
and will pass the gene and the disease to 100% of it's offspring.
and will pass the gene and the disease, on average, to 50% of its offspring.
It does not have the disease, nor can it be passed on.
If there is a test, why is it still so common?
Over the years, many breeders have found that due to the electrical firing of the muscles in afflicted horses they were easier to "fit" for halter without requiring as much physical exercise. This led to some breeders exploiting the "benefits" of a known disease and breeding it forward to more horses instead of breeding it out.
An example of this was seen at the 2004 Appaloosa World Show Sale. The top selling mare sold for $14,000.00 had a status of N/H. This fact was published in the sale catalog as well as on the pedigree sign on her stall. Now honestly, I can't say for sure what the new owners plan to do with her. It is possible that she will spend the rest of her days in a non-breeding role, but with a that price tag, I doubt it.
I will say that during the 2006 Appaloosa World Show Sale, I saw an increased awareness of the status of horses. Horses brought into the ring without disclosed statuses were asked about, and several that had N/H were low selling horses. Still, if the horse had a big named breeder behind it, it sold high, but at least the general public has taken an interest in at least slowing the spread of HyPP.
HyPP will continue to be bred forward until we are able to get all applicable Associations who register horses with Impressive breeding, to pass rules on mandatory testing for HyPP and to stop breeders from passing forward this terrible disease.
- January 1, 2007 was the date set to no longer allow registry of foals testing H/H at the 2004 AQHA convention. Mandatory testing for HyPP was also put into ruling at the convention. N/H was tabled until a later time.
- The Appaloosa Association followed suit with their date to disallow registry of H/H foals beginning January 1, 2008.
While this is good news for the horse industry, it is not good enough. We still need rulings on N/H and participation from the rest of the registries on H/H. The APHA did not pass rulings in any category at their 2004 convention. There are also many part and half blood registries who need to follow suit and pass rulings on both positive statuses and mandatory testing thereof.
