A gene mutation that can cause the muscular disease myotonia has been discovered in New Forest ponies in England.
Congenital myotonia has never before been diagnosed in New Forest ponies.
Myotonia is a hereditary muscular disease. In goats and some dog breeds, a disruption in the development of the ion channels results in involuntary muscular contractions that can become aggravated by excitement. A specialised research laboratory at the University of Bern, Switzerland, has been asked to conduct exhaustive genetic research into this phenomena.
Now, researchers at the Utrecht University Equine Clinic, in The Netherlands, have discovered a mutation in the DNA of the New Forest pony that can cause the disease.
In New Forest ponies, a DNA defect seems to disturb the development of a protein, resulting in the symptoms of myotonia in foals.
In 2009, Dr Inge Wijnberg, a specialist in equine internal diseases at the clinic, noticed a foal that fell down after running in the pasture.
“With the help of the foal’s breeder and other respected breeders, we were able to conduct a detailed genetic diagnosis, including studies of the foal’s parents.
“We were able to deterimine that the disease only manifests itself through clinical symptoms if both parents pass on the defective gene to the foal.”
Researchers are currently studying which stallion lines carry the defective gene in order to initiate a rapid and effective approach to prevent the spread of the disease among New Forest ponies.
“Ideally, we would like to set up an extensive programme to prevent the breeding of foals with congenital myotonia,” Wijnberg says.
Foals with myotonia cannot be used as athletic or recreation horses, and even at rest they can display symptoms. At the moment, there are no European guidelines and studbooks are free to decide whether or not to breed animals with congenital defects.
“The breeders of New Forest ponies are very professional, and they are doing their utmost to assist in prevention efforts.”
“A missense mutation in the skeletal muscle chloride channel 1 (CLCN1) as candidate causal mutation for congenital myotonia in a New Forest pony”; Wijnberg ID, Owczarek-Lipska M, Sacchetto R, Mascarello F, Pascoli F, Grünberg W, van der Kolk JH, Drögemüller C, see: http://www.ncbi.nlm.nih.gov/pubmed/22197188.