Polysaccharide Storage Myopathy (PSSM)
Polysaccharide Storage myopathy (PSSM1) –
Animal Genetics has been working with several breeders of Gypsy horses to better understand the effects of PSSM1 in the breed.
The work was specifically focused on several key factors including whether or not PSSM1 existed in the breed, if the genetic test being offered is valid, what additional factors may influence PSSM1 in the breed, and can the condition be managed.
We now have several examples of horses that have tested positive genetically with 2 copies of the mutated gene and have had episodes of tying up, muscle stiffness, sweating, and reluctance or inability to move. Muscle biopsies of these horses were collected during these episodes by veterinarians for further testing. In all cases, muscle biopsy results of affected horses showed a dramatic accumulation of excess glycogen and abnormal polysaccharides. All symptomatic horses were homozygous for the genetic variant. In this relatively small study (roughly 50 horses) all horses with one copy of the mutated gene did not exhibit any clear symptoms. However, several horses did show elevated levels of glycogen in muscle tissue samples compared to those horse that tested negative for the genetic mutation.
In each case the symptomatic horse was properly managed through restricted diets and increased regular physical activity. Symptoms related to PSSM1 in all horses decreased or went away completely with in a relatively short period of time. We hope to be able to continue to evaluate all effected horses in the future to help us better understand the condition.
Further work and more details will be published in the future but Animal Genetics wanted to get this out to people who have been waiting for information about PSSM1 in Draft breeds like the Gypsy horse as soon as we could. It is our opinion that in all most all cases the effects of PSSM1 in Gypsy horses can be manage if the condition is identified properly.
Animal Genetics will continue to work with breeders and veterinarians to better understand the condition and identify additional genetic factors that may influence a horse with two copies of the mutated gene.
Foal Immunodeficiency Syndrome (FIS) in Gypsy Horses
Foal Immunodeficiency Syndrome (FIS) – is a recessive genetic disease that primarily affects two relatively rare native UK pony breeds, the Dales and the Fell pony. FIS is caused by a single mutation in the sodium/myo-inositol cotransporter gene (SLC5A3).
This gene plays a vital role in the regulatory response in many tissues including lymphoid tissues. As much as 10% of all Fell ponies born each year suffer from FIS. This has put a strain on the long-term survival of this breed as well as the likely spread of FIS into other breeds. Most recently Animal Genetics has found the mutation that causes FIS in approximately 9% of Gypsy horse breeds in the US and Europe.
Foals must have two copies of the mutated gene in order to be affected with FIS. Therefore, each parent must be a carrier of the mutated gene in order to have an affected foal. Affected foals appear healthy and normal at birth but begin to show signs of weakness, dull coat and anorexia at 2-3 weeks. The first clinical signs of this disease include diarrhoea, nasal discharge, poor growth, pale gums and decreased appetite. Vision may be affected, presumably due to secondary bacterial infections. Mortality rate for foal affected by FIS is 100% despite intensive treatment. All FIS affected foals generally die or are euthanized before they reach the age of 3 months.