| Breeder Education: Genetic Disorders in Arabian Horses |
| Cerebellar abiotrophy (CA) |
| Contributed by Lisa Goodwin-Campiglio on Spanish Arabian Promotion (SAP) Group. Cerebellar abiotrophy (CA), also referred to as the cerebellar cortical abiotrophy (CCA), is a genetic neurological disorder in animals best known to affect certain breeds of horses, predominately arabians, dogs and cats. It is inherited as an autosomal recessive gene, which means it is not sex-linked, and the allele has to be carried and passed on by both parents, simultaneously, in order for an affected animal (CA/CA) to be born.. Horses that only carry one copy of the gene are referred to as Carriers (N/CA), may pass it on to their offspring, but themselves are perfectly healthy—without any sign of the disorder. Because it is recessive, the allele for CA may pass through multiple generations before it is expressed. Clear animals (N/N) do not posses the defective mutated allele and therefor can not pass it forward. Caused by the inability of the Purkinje neurons in the cerebellum to develop properly and to regenerate, this condition is noticeable when the animal is less than six months old. Sometimes the onset of clinical signs is gradual and the animal is much older before the owner or caretaker notices a problem. Such cases have been observed as late as 18 months to 3 years old. CA cannot be prevented, other than by selective breeding to avoid the gene, and it cannot be cured. This disorder has been historically documented since 1837 and is considered as established 'In the Arabian Breed' encompassing almost all bloodlines. In addition to dogs and horses, there also have been cases of cerebellar abiotrophy in Siamese and Domestic short-hair cats; in Angus, Polled Hereford, Charolais and Holstein Friesian cattle; Merino and Wiltshire sheep; Yorkshire pigs and recent cases in 2009 were found in a herd of domestically bred Elk. Cerebellar abiotrophy in horses was originally thought to be a form of cerebellar hypoplasia and was described as such in older research literature. However, it was discovered that in horses, the die-off of Purkinje cells began after the animal was born, rather than occurring in utero. There are other diseases that lead to cerebellar degeneration, but the loss of Purkinje cells is a clear way to diagnose CA, and the combination of clinical signs is sufficiently unique that CA can easily be distinguished from other conditions, even in a living animal. Clinical signs in horses include ataxia or lack of balance, an awkward wide-legged stance at rest with the forelegs spread and hocks close together, a head tremor (intention tremors), hyper-reactivity, lack of menace reflex, stiff or high-stepping gait in the forehand, coarse or jerky head bob when in motion (or in very young animals, when attempting to nurse), apparent lack of awareness of where the feet are (sometimes standing or trying to walk with a foot knuckled over), poor depth perception, and a general inability to determine space and distance. The clinical signs are, when taken as a group, fairly unique and not easily mimicked by other illnesses, though certain types of neurological injury and infection do need to be ruled out in order to avoid confusion with Wobbler's syndrome, Equine Protozoal Myeloencephalitis (EPM), and injury-related problems such as a concussion. Until September 2007, verifying the diagnosis in a laboratory setting was only possible by examining the brain post-mortem to determine if there had been a loss of Purkinje cells. An indirect DNA test which identifies markers associated with cerebellar abiotrophy is available at the Veterinary Genetics Laboratory at the UC Davis School of Veterinary Medicine in California. Researchers working on this problem include Dr. Cecilia Penedo, PhD, at UC Davis and her assistant Leah Brault. http://www.vgl.ucdavis.edu/services/horse.php The same indirect DNA test is also avalable at The Dr. Van Haeringen Laboratorium bv, The Netherlands for CA testing in Europe. English and Dutch. No import paperwork necessary for EU members. Processed samples are sent to UC Davis for confirmation. A fully informative website of CA, including a Publically Disclosed Status List, photos and videos is available at: http://cerebellarabiotrophy.webs.com/ Support research on this disorder. Test before breeding. Avoid the loss and heartbreak of an Affected foal. |
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| A page on our site is dedicated to SCID and a foal that died from this disorder. Click the link below for more information. |
| Announcement Musica Sonadora (Filly by Que Serena X ZLA Ezio) has crossed the rainbow bridge on October 14th 2009. She died from the devastating effects of SCID Click here to read our story & for more information on this genetic disorder. |
| For Information on LFS or Lavender Foal Syndrome you can read this fact sheet by James Baker from Cornell University. Lavender Foal Syndrome (LFS) |
| Note: Our Spanish Arabian Stallion ZLA Xochtiel who is standing at stud has tested CA N/N, and is SCID clear. Our Arabian mares, and the colt RSA Mahogany Sin will be tested in the near future. |