Warmblood Fragile Foal Syndrome

The HHSA committee has been monitoring information regarding a rare genetic disorder referred to as Warmblood Fragile Foal Syndrome WFFS): Warmblood Fragile Foal Syndrome (WFFS)

WFFS foals exhibit extreme skin fragility, especially at the joints. This disease cannot be treated or cured and is invariably fatal, typically soon after birth. This disease manifests itself only when a foal receives a copy of a certain recessive gene from each of its parents. Only horses that are homozygous for this condition (that is, horses that carry two copies of the recessive gene) exhibit the full effects of the syndrome. Horses that are heterozygous for this condition (that is, horses that only carry one copy of the recessive gene received from either parent) are referred to as “carriers” of the gene, but otherwise display no known outward effects of the disease. WFFS requires two copies of this gene for expression (referred to as a recessive autosomal trait), so a single copy can be carried through multiple generations of animals before being expressed. (Excerpt from AHU announcement June 2018)

At present in Australia, Practical Horse Genetics located in NSW, has a commercial test available for detecting this autosomal recessive gene. Racing Australia, which currently handles genetic parentage verification for the HHSA, may have the technology to provide the WFFS testing in future. For now, HHSA members may wish to consider having their breeding animals tested to determine whether any are carriers and to develop strategies for avoiding matings between two carriers.

How to Test Your Horse

Click the link below for instructions on how to test your horse.

https://www.practicalhorsegenetics.com.au/

Testing Discounts

The discount code for you to use is HHSAFF (ie. HHSA fragile foal).

It is to be an ongoing code which can be used in future breeding years. There will be quite a few people wanting to test before this breeding season, but there will also be extra testing for a few years from now as young stock reach breeding age and as people decide to test mares as well as their stallions.

This discount will take the normal price for WFFS testing from $54 including GST to $48 including GST.

The individual horse owner orders, pays, and sends in DNA samples. Results are private and only sent back to the horse owner, not HHSA.

It is fine for owners to add any other DNA testing that Practical Horse Genetics offer and still use that discount code (for example colour testing).

Please read more information concerning WFFS in the link below:

Horse Genetics Resources – WFFS

If you are unlucky enough to have an equine abortion in the 2018/2019 breeding season please contact Dr. Kao Castle as Practical Horse Genetics have also decided to offer free WFFS testing on aborted Warmblood foals. Owners wanting to send a sample for testing should call Dr. Kao Castle on 0410 492 005 to let them know a sample has been retrieved from the aborted foal and verify what kind of tissue sample to provide the lab. This sample will depend on the state of the foetus and how quickly it can be shipped to Dr. Kao.

In all cases, only want a small amount of tissue is required for testing: no more than a teaspoon full in terms of volume. If the sample can’t be shipped immediately it should be stored in a ziplock bag in the freezer. They will also want to know whether the abortion was a red-bag delivery and whether any other abnormalities were noted.

The aim of this testing is to clarify whether any of these pregnancy losses are due to WFFS.

WFFS syndrome and what it means for breeders and horse owners

The Celle State Stud has recently released results of genetic tests for Warmblood Fragile Foal Syndrome (WFFS) for all stallions standing at stud. In future, stallions presenting for Hannoveraner Verband licencing require the genetic test for WFFS. Any Hanoverian broodmare sired by a known carrier should be tested for her genetic status, and a carrier mare should be only bred to a known negative stallion. Only foals inheriting the genetic defect from both, mare and stallion, can be affected by the lethal syndrome. Stallions which are confirmed carriers can be still bred to tested negative mares, and the resulting progeny should be genetically tested before entering breeding.

WFFS – knowledge is key

Warmblood Fragile Foal Syndrome (WFFS) is much reported on right now, and with good reason. Any breeder should understand what it stands for and what it means in practical terms. WFFS is a genetic syndrome which was first reported in 1984, and a genetic test exists commerically since 2013. Foals which are affected are not viable (which means they cannot live) but, according to current knowledge, carriers who still have one healthy, not affected gene, are not affected health-wise at all, nor are they expected to develop problems later in life. However, a carrier, whether male or female, can pass on the mutation if used in breeding, and that is why breeders need to be informed.

In exemplary fashion, Celle State Stud has recently released the results of the genetic tests for all stallions standing at stud in Celle. Several stallions have been identified as carriers of the mutation. This means that progeny of those stallions can be carriers as well. It is important to note that for owners of sport horse progeny from these stallions, there is no reasons for concern for the health of the horse.

Broodmares sired by the affected stallions should be prioritised for genetic testing, as they have a 50% chance to be a carrier of the gene, and if bred with a carrier stallion, have a 25% chance of an affected foal. A broodmare which has been identified as a carrier can still be bred to a stallion who has been tested and proven to be not a carrier, and the foal will not be affected by the carrier, although the foal will have again a 50% chance of being a carrier, and hence should be genetically tested.

This also means good mares should not be excluded automatically from breeding if they are identified as carriers. A responsible breeder will choose a confirmed non-carrier (negative) stallion, and test the resulting foal for future information.

The reverse holds true as well: stallions identified as carriers can be bred to mares which have been genetically tested and shown not to carry the mutation, and the resulting foal will not be affected by WFFS but they have a 50% chance of carrying the mutation. This is important to keep in mind if you were considering using one of the carrier stallions: if the mare has been tested and is not a carrier, the stallion can be used, and the foal will not develop WFFS, but it may be a carrier itself and hence should be tested.

Regardless of whether the carrier parent was the stallion or the mare, if the foal or progeny is tested and does not carry the mutation, then there is no further risk of the syndrome re-surfacing. This means, if you own a mare sired by an identified carrier stallion, you should as a matter of priority have the mare tested for her WFFS status. If she is not a carrier, then there is no future problem even though she has the carrier stallion in her pedigree. If she hasn’t inherited the carrier gene she won’t acquire it later. Hence it is of paramount importance to test progeny of the identified stallions, and this is why it is so useful that Celle State Stud has released this information.

Stallions of Celle State Stud which have been confirmed as carriers are Balou Peggio, Chivas, Comte, Don Frederico, Don Index, Don Romanov, Don Vino, Edward, Londonderry, Londontime, Quaterhall and Sarotti Mokka Sahne (https://landgestuetcelle.de/de/zucht/hengstsuche/; accessed 16/10/2018). Other known carriers include Quantensprung (Klosterhof Medingen).

In summary

• Ideally all broodmares should be tested for the WFFS mutation
• Mares sired by identified carriers, or of stallions of unknown status, should be prioritised for testing and not be bred to carrier stallions
• Identified carrier stallions can still be used to breed with tested mares, keeping in mind that the resulting foals will have a 50% chance of being carriers themselves
• Sport or leisure horses carrying the mutation are not known be affected in health
• Any filly foal born to a carrier should be tested as she might become a broodmare

The Hanoverian Horse Society of Australia will continue to communicate to our members as more information and updates become available.

In closing, we would like to thank you for your continued interest and passion for the Hanoverian breed.

References

Monthoux, C., de Brot, S., Jackson, M., Bleul, U. & Walter, J. (2015). Skin malformations in a neonatal foal tested homozygous positive for Warmblood Fragile Foal Syndrome. Bmc Veterinary Research 11: 8.

Winand N. Identification of the causative mutation for inherited connective tissue disorders in equines. “United States Department Of Commerce Application Number: 61/486,464; (Filing Date: May 16th, 2011).”

Witzig P, Suter M, Wild P, Rao VH, Steinmann B, Von Rotz A. Dermatosparaxis in a foal and a cow–a rare disease? Schweiz Arch Tierheilkd. 1984;126:589–96.

About the author: HHSA shadow registrar Dr Sabine Schmoelzl is a veterinary scientist working in livestock reproduction and phenomics research, with a PhD in Molecular Breeding.