Cerebellar abiotrophy (CA) also referred to as cerebellar cortical abiotrophy (CCA) is a genetic neurological disease in animals best known to affect certain breeds of horses and dogs. It has been observed in Arabians and their derivatives, the Miniature Horse, the Gotland Pony, and possibly the Oldenberg. Aslo seen in Siamese Cats; in Angus, Polled Hereford, Charlois and Holstein Friesian cattle; Merino and Wiltshire sheep; and Yorkshire pigs. There is no cure.
It develops when neurons known as Purkinje cells in the cerebellum of the brain begin to die off. These cells affect balance, coordination, and fine-tuned movements. They have a critical role to play in the brain. The Purkinje layer allows communication between the cortical layers in the cerebellum. Put simply, without Purkinje cells, an animal loses its sense of space and distance, making balance and coordination difficult. In most cases, the neurons begin to die off shortly after the animal is born within the first 90 days post-partum. The condition is usually noticable when the foal is less than six months old, though sometimes the onset of symptoms is gradual and the foal is much older before the owner or caretaker notices a problem. Most cases are noticed either at weaning if stressful or when the youngster is brought up for handling and further training.
Cerebellar abiotrophy in horses was originally thought to be a form of cerebellar hypoplasia and was described as such in older research literature. There are diseases that cause other types of 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 is unlikely to be confused with other conditions.
CLINICAL SIGNS (Symptoms):
Ataxia or lack of balance, an awkward wide-legged stance in the forehand with hocks close together, a palsey-like head tremor (intention tremor), hyperreactivity, lack of menace reflex (third eye lid has retarded blink or none at all), stiff or high-stepping gait shooting from the shoulder 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.
Affected horses are accident prone, tend to run into solid objects, fall to the side if rearing up and often bang their heads causing many owners ( and vets) to think that a severe head injury is the cause of the ataxia. The affected horse has normal intelligence, clear vison, good appetite and no atrophy or muscle waste.
In horses, CA is inherited as a monogenic autosomal recessive gene. This means it is not sex-linked, and the gene has to be carried by both parents in order for an affected animal to be born. Horses that only carry one copy of the gene may pass it on to their offspring, but themselves are perfectly healthy--without any clinical signs of the disorder.
University of California, Davis, USA: (Pre-testing available)http://www.vgl.ucdavis.edu/services/horse.php
This article has been written for sE.com by Elizabeth Goodwin-Campiglio. To see more articles also written by this author/researcher see:
In collaboration with Brenda Wahler.
- Cerebellar Abiotrophy (CA): A Review at http://www.arabianhorses.org/education/genetic/default.asp
in collabration with Brenda Wahler and reviewed by current researchers as stated on the document.
- Cerebellar Abiotrophy and the Horse Genome Project athttp://www.arabianhorses.org/education/genetic/default.asp
written by Elizabeth Goodwin-Campiglio and reviewed by Mesrs. Drs. Gerber and Leeb.
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