The rare genetic mutation that results in Warmblood Fragile Foal Syndrome (WFFS) had been fairly unknown, until suddenly gaining significant media attention in early 2018.
The syndrome is characterised by soft tissue abnormalities that display in the form of extremely fragile and friable skin, lax and hyper-extensible limb joints, as well as lesions on mucosal surfaces. Skin may tear and ulcerate easily as a result of contact with normal surroundings. The condition is fatal, due to the high rate of infections of lesions and skin tears. Foals are usually euthanised within a few days of birth.
The recessive mutation will only result in an affected foal if the genotype of the foal is homozygous for the recessive gene. When breeding to two carriers (N/WFFS) to each other, there is a 50% chance that offspring born are also carriers. The chance of an affected foal (WFFS/WFFS) when breeding two carriers to each other is 25%, as is the chance of breeding a non-carrier (N/N).
Since an affected foal inherits the disease by receiving one defective gene from each parent, the birth of affected foals can be prevented by breeding a carrier to a non-carrier. In this case there is an equal chance of producing a non-carrier or a carrier foal.
There are various reported statistics on the prevalence of carriers in the warmblood population. Some references cite around 6%, whereas some even cite around 10% or 11%. This is an indication that we do not know enough about the disease, as a much bigger population of horses needs to be tested for carrier status to obtain statistically significant numbers.
The WBFSH continues to believe that the condition requires a measured and considered response. Every foal lost has a significant impact, either emotional, financial or both, on the breeder and the mare.
Therefore, the President of the WBFSH considered it a priority that more information became available through research and collection of accurate statistics, in order to obtain a clear picture of the impact or potential impact this disease may have on the warmblood breeding industry. Current statistics may not be accurate due to unknowingly undiagnosed cases of affected foals born or pregnancies aborted.
The WBFSH studbook members have been acting responsibly, giving their breeders sound advice and recommending the testing of breeding stock, enabling breeders to make informed choices when selecting stallions for their mares. This is an important part of responsible breeding and horse welfare and should always be at the forefront of every breeder’s mind in breeding matters in general.
During the WBFSH General Assembly in Hungary in December 2018, WFFS was discussed as a significant part of the organisation's engagement with and commitment to equine health and welfare.
Diagramatic Representation of WFFS Inheritance