Registry Services - Genetic Disorders
HERDA

HERDAHereditary Equine Regional Dermal Asthenia, also known as Hyper Elastosis Cutis or HC

HERDA is a painful but rare skin condition characterised in afflicted horses by skin lesions. It most often occurs along the back, particularly the saddle area and the neck but has also been known to show up on other parts of the body, including the legs.
Basically, a HERDA afflicted horse’s skin has ‘faulty’ or defective fibres which act to prevent the three layers of skin binding together properly. The weakened fibres cannot stand up to any external stress or strain. Consequently, when the skin is damaged, it fails to heal properly leaving it open to infection and can in the most extreme cases ‘de-glove’ the horse - effectively skinning it alive. Unfortunately, because of the nature of HERDA and the weakened state of the fibres, the skin cannot be stitched back together.

In most cases horses don’t show any visual signs of the disease until they are around 2 years of age and have begun their initial training. Occasionally, HERDA does become apparent earlier if an afflicted horse becomes injured in the paddock.

Tragically, there is no cure for HERDA as it is a genetic disorder. Most horses diagnosed as afflicted with the disease are euthanized because they can no longer be ridden due to the injuries they suffer whilst saddled. Anecdotally, most afflicted horses are unlikely to have an extended lifespan.

However, after extensive expert scientific research, what we DO know is that HERDA is a recessive genetic disease so both sire and dam must possess the recessive gene in order for offspring to possibly be afflicted with HERDA.

 

The Genetics of HERDA

There has been considerable research into the genetics of HERDA and with the advent of reliable DNA screening it can now be decisively concluded afflicted with the disease. Sounds confusing?  Now would be a good time to explain the terminology so that the table below is fully understood.

A normal horse is a horse that carries no copies of the gene and in genetic terms is depicted as N/N.
A carrier horse is a horse that carries one copy of the HERDA gene and in genetic terms is depicted as N/Hr. It is important to note that carrier horses do not show the symptoms of HERDA.

An afflicted horse is a horse that carries 2 copies of the HERDA gene and in genetic terms is depicted as Hr/Hr. It is important to know that an afflicted horse will, at some stage, display the symptoms of HERDA and in a large majority of horses this will ultimately be fatal.

At this point in time it is apparent that Quarter Horses diagnosed with HERDA (either carrier or afflicted) have been genetically linked to the famous American Quarter Horse sire, POCO BUENO.


HERDA



The Role of AQHA in Managing HERDA 

AQHA’s prime responsibilities are to act as custodian and protector of the stud book which includes responsible policy on the management of genetic disorders by providing reliable information for AQHA members and Quarter Horse enthusiasts generally.
AQHA has been working tirelessly behind the scenes to facilitate testing for its members. HERDA Test Kits are now available from AQHA for AU$55, which uses the same testing process as AQHA’s current DNA Testing Kit.  This means that members will also be familiar with the process.

In the meantime, if you are not sure – or need to clarify – any information please contact AQHA so we can assist you with any concerns or questions you may have. 

  1. Effective 1 January 2008,if you would like to test your horse for HERDA and have the results accepted by AQHA, you must have been issued an AQHA HERDA testing kit.  These are available for $55 through the office. 
  1. Effective 1 January 2009 all new colts and stallions going through the IBF process will be required to have HERDA testing done before they will be accepted as a breeding sire with the Association unless it can be proven the horse DOES NOT contain any lineage to POCO BUENO in it pedigree.
  1. Effective 1 January 2008 all new Foundation Stock recording applications will require HERDA testing on top of the already required DNA, OLWS and HYPP testing.  A negative test must be achieved before they will be accepted into the Foundation recording system.
  1. Effective 1 January 2009 all new registrations: if the horse’s pedigree DOES NOT contain any POCO BUENO lineage the progeny will not be required to be tested.
  1. Effective 1 January 2009 any horse imported into Australia not carrying POCO BUENO lineage will not be required to be tested

Members with breeding mares that have linage to the stallion POCO BUENO (USA 3044) are encouraged to test for HERDA so they can make educated decisions when choosing a stallion to send their mares to.  AQHA would like to stress that this disease is active within all Quarter Horse disciplines and warn that HERDA testing of all breeding stock with lineage to POCO BUENO is highly recommended.

If you have any queries in regard to the new regulations or would like to discuss HERDA or our method of testing, please contact the AQHA Registry Department on (02) 6762 6444.

 

Frequently Asked Questions 
                

Q: 

Do only Quarter Horses get HERDA?

A: 

No. Other breeds and species have been found to exhibit a similar condition. Other breeds with some Quarter Horse bloodlines have been diagnosed with the disease including Paints and Appaloosas.

 

 

Q: 

Is HERDA contagious?

A:

Absolutely not. HERDA is a genetic disorder. The disease has to be inherited from one or both parents.  It is not transmitted through air.

 

 

Q:

Do I have to have my horse tested for HERDA?

A:

Notwithstanding the current rule changes for imports or breeding sires, no. However AQHA does recommend testing if your horse does contain lineage to POCO BUENO. You may also wish to have your horse tested for your own peace of mind.

 

 

Q: 

What is AQHA doing about HERDA?

A:

AQHA has implemented HERDA testing to responsibly attempt to manage and control the condition.

 

 

Q:

I have read and heard a lot of conflicting information about HERDA – who do I believe?

A:

 Please contact AQHA with any further queries.

 

 

Q:

Where did HERDA come from?

A: 

HERDA was initially diagnosed in the United States of America; however it has now been diagnosed in a number of countries including Australia.  Now, with a reliable test available, breeders can make educated decisions when planning to purchase or breed.

 

 

Q:

What can I do to prevent my horse from getting HERDA?

A: 

As HERDA is genetic only and not contagious, your horse cannot ‘catch’ HERDA from either a carrier or an afflicted horse. Its HERDA status will already be genetically determined.  Therefore, be sure to check the breeding of your horse; look for clinical signs (bearing in mind that carriers do not display any) and have your horse tested for peace of mind.

 

 

Q:

Is AHQA going to de-register horses that are found to carry HERDA?

A: 

No. Deregistration is not an option as far as AQHA is concerned. However, as part of AQHA’s responsible management, we will require a certain number of horses be tested, their HERDA status printed on their Certificate of Registration and noted in the horses’ information on the AQHA website.

 

 

Q:

What are the chances that my horse carries HERDA?

A:  

If your horse has lineage to POCO BUENO then there is always a chance, but this chance is minimal unless there are a number of crosses of this stallion on both sides of your horses’ pedigree - the more crosses, the greater the chance. Only testing will determine for certain.

 

 

Q:

Will I be able to breed with my mare if she has HERDA?

A:

If your mare is a carrier of HERDA then breeding is still possible.  However, you will have to monitor what stallions you serve her with to avoid producing an afflicted foal. With a carrier mare, by avoiding mating with carrier stallions your offspring could be normal (N/N), but there is a 50% chance of their offspring being a carrier due to your mare being a carrier.

 

 

Q:

Should I avoid purchasing HERDA horses?

A:

This is a personal choice. If a horse carries HERDA it will present as a healthy horse and will be able to perform in the ring and possibly in a breeding program – (once again this is a personal choice).  When breeding with a horse that carries HERDA, you have to make sure the horse you mate it with is not a carrier, so it comes down to an educated and monitored breeding decision.

 

 

Q:

Should I avoid sending my mare to a stallion that carries HERDA?

A:

Once again, this is a personal choice. You should avoid stallions that carry the disorder if you mare is also a carrier.  If your mare is not a carrier and you put her to a stallion that is, remember, you have a 50% chance of your foal also being a carrier, which will present as a healthy foal. 

 

If your mare is a carrier and you put her to a HERDA carrier stallion, you have a 1 in 4 chance of getting a foal that will be afflicted, which will not be eligible for registration and may have to be put down.

   

Q:

My horse has been tested and is HERDA afflicted.  Should I sell it or put it down?

A:

This is an extremely hard question and a decision that only you can make in consultation with your vet. Life for an afflicted horse can be a painful and heartbreaking one, especially in the knowledge that the vast majority of afflicted horses will ultimately die prematurely as a result of the condition.

 

We hope this has assisted to clarify the genetic disorder HERDA. However should you require any further information or testing kits, please contact the office 02 6762 6444.

 

 

Australian Quarter Horse Association
Lot 13 Jack Smyth Drive, Hillvue NSW 2340 (opp. Main doors of AELEC)
PO Box 979, Tamworth, NSW 2340
Phone: (02) 6762 6444 Fax: (02) 6762 6422 
ABN: 41 000 964 643

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