Cerebellar Abiotrophy A Serious Inherited Condition In Arabians

Tags: Cerebellar Abiotrophy, Arabian, Arabian Horse, Genetic Disorders, Health, Degenerative Disorders

 

Equine CA or Cerebellar Abiotrophy, found almost solely in the Arabian horse bloodlines, is a neurological, genetic condition. Most foals appear normal and show no sign of cerebellar abiotrophy at birth but noticeable symptoms usually appear around four months of age. There are some cases where the first symptoms of cerebellar abiotrophy appeared in foals only a few days old or horses over a year.

Cerebellar abiotrophy develops when the neurons recognized as Purkinje cells, located in a region of the brain called the cerebellum, start to die off shortly after birth. It affects a horse's coordination and balance under six months of age but because of the gradual onset of CA symptoms, caretakers or owners often do not notice any physical problems in affected horses until they are much older. A horse without Purkinje cells has no sense of distance and space. Scientists believe an autosomal recessive defective gene links cerebellar abiotrophy in horses, meaning it is not sex-linked. It is possible to pass this gene forward without CA reappearing for several generations. For a horse to be born with cerebellar abiotrophy, both parents must carry the gene. When horses carry only one copy, they might pass this to their foal, although they have no symptoms of CA and are perfectly healthy themselves.

Symptoms of cerebellar abiotrophy include hyperactivity; lack of balance; uncoordinated muscle movement; palsy-like head tremor or shaking; a high stepping, awkward, or stiff gait; poor or no depth perception; abnormal blink response; ungainly wide-legged stance; and no awareness of feet position. There is a jerky or coarse head bob when a foal tries to nurse or when a horse is in motion.

Most horses affected with cerebellar abiotrophy have average intelligence but are accident prone due to the disease. Foals with CA often fall down or run into things causing head and other injuries. If not severe enough to require euthanasia, the symptoms of CA stabilize over time, although they often worsen for six to twelve months after onset. Some evidence suggests that horses affected with cerebellar abiotrophy cognitively learn other methods to determine distance or for moving, so they are less accident-prone, but only appear to improve. Many owners of foals displaying mild to severe symptoms of CA including a severe lack of balance, exaggerated gaits, or even just a slight head tremor often choose euthanasia regardless of the symptoms severity. One reason for this is that the horses do not have the required coordination for riding them safely so the horses pose a danger to themselves because of this.

For cerebellar abiotrophy in horses, no DNA test is currently available. Because there is no way to cure cerebellar abiotrophy, the only means to prevent CA in horses is to avoid the gene using selective breeding. To diagnose a horse with cerebellar abiotrophy, after ruling out specific types of neurological infection and injury, requires examining the cerebellar abiotrophy symptoms as a group, because they are distinctive and not easy to mimic. There are also a series of neurological tests veterinarians perform to ascertain CA consistent symptoms. The only way to diagnose cerebellar abiotrophy positively is a post-mortem cerebellar tissue, histological examination.

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