Cerebellar Abiotrophy (CA)
Gene or Region: MUTYH
Reference Variant: C
Mutant Variant: T
Affected Breeds: Arabian and Other Breeds
Research Confidence: High Confidence - Findings reproduced in multiple studies
Explanation of Results: ca/ca = homozygous for Cerebellar Abiotrophy, trait expressed ca/n = heterozygous for Cerebellar Abiotrophy, carrier n/n = no variant detected
General Description for Cerebellar Abiotrophy
Cerebellar Abiotrophy (CA) is a degenerative neurological disorder due to the death of large neurons (Purkinje cells) in the cerebellum. Foals affected by CA begin show symptoms between 6 weeks and 4 months of age. These horses display head tremors, lack of coordination, wide stances, exaggerated gait, difficulty rising, and startle easily. As this disease is an autosomal recessive condition, a horse must inherit two copies of the allele (ca/ca) to show any signs. Horses with only one copy of the allele (ca/n) are known as carriers due to their ability to produce affected foals.
Here is a video taken at the University of Zurich in 1992 of a CA/CA foal.
Gene Information
MUTYH is an enzyme that functions to repair oxidative damage, and is expressed at high levels in the brain. Although many other species are also affected by CA, the horse is the only one associated with mutations in this gene. This particular mutation is located a short distance from MUTYH, and is likely involved in its regulation.
References
Brault LS et al., “Mapping of equine cerebellar abiotrophy to ECA2 and identification of a potential causative mutation affecting expression of MUTYH.” (2011) Genomics. 97: 121-9. PMID: 21126570
Brault LS and Penedo MC, “The frequency of the equine cerebellar abiotrophy mutation in non-Arabian horse breeds.” (2011) Equine Vet J. 43: 727-31. PMID: 21496100
Cavalleri JM et al., “Morphometric magnetic resonance imaging and genetic testing in cerebellar abiotrophy in Arabian horses.” (2013) BMC Vet Res. 9: 105. PMID: 23702154
Tarr CJ et al., “The carrier prevalence of severe combined immunodeficiency, lavender foal syndrome and cerebellar abiotrophy in Arabian horses in South Africa.” (2014) Equine Vet J. 46: 512-4. PMID: 24033554
More Horse Health
Severe Combined Immunodeficiency
Severe Combined Immunodeficiency Disease (SCID) is a condition in which affected foals are unable to mount an effective immune response after infection and are unable to recover from infections that unaffected foals would easily resist. The disease is universally fatal in horses, usually within 4-6 months of life.
West Nile Virus Symptom Susceptibility / Risk
West Nile Virus (WNV) is a mosquito-borne virus that can infect multiple types of mammals, including horses. Infection can lead to a series of severe symptoms, most commonly encephalitis – acute inflammation of the brain. Severe neurological symptoms develop in ~8% of exposed horses, and once symptoms manifest, the fatality rate ranges from 20-40% and is higher in older horses.