HYPP - Quarter Horses and derivatives from the 'Impressive' line
HERDA - Appaloosa and derivatives from Poco Bueno
SCID
CA - Arabs
Lavender Foal
OLWS - mainly Paints and Pintos
FIS - Fell and Dales ponies
Friesian Horses - Multiple issues
However horse breeders are not alone in dealing with such issues; all other species have their own problems. It is how these problems are dealt with by the 'custodians' of the breed/s which separates the 'men from the boys'.
Open acknowledgement that a problem exists is the first requirement.
Informed decision making is the second.
Acting upon the informed decision made, is the third.
The following post and illustration is about Dairy Cattle. For those who take the time to read this you will find it very informative and helpful as it is very relevant to the HWSS issue.
LIC (short for Livestock Improvement Corporation) is an international artificial breeding company which supplies and trades frozen bull semen throughout the world. They are an industry leader in the area of genetic research in dairy cattle.
LIC is a player in the dairy industry in Ireland supplying semen and expertise to farmers in this country. This small calf syndrome 'problem' will be present in Ireland.
"The average herd
of 400 cows could expect to have 60 cows which are carriers. If this
herd was mated to a cross-section of Holstein Friesian bulls in New
Zealand, LIC expects one to two calves would result.
Putting this into perspective, since the 1960's a quarter of one
percent (0.25%) of calves bred from Holstein Friesian or crossbred type
animals each season are likely to have been affected by the Small Calf
Syndrome."
Present research would suggest that in some countries, HWSS has a similar if not higher level of carriers, in the population as a direct result of the overuse of certain sires, to the level seen for small calf syndrome in Holstein-Freisian cattle and their cross-breds.
LIC discovers small calf gene : the full text for the graphic below.