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Inherited diseases of arabian horses
In the world the most common and often the only possible method of breeding is the pure one. On the one hand, it allows to consolidate valuable genetic complexes in the animal, and on the other hand it promotes to contribute the accumulation of mutant alleles. As a result of prolonged use of pure breeding the level of inbreeding can increase. It increases the probability of transition of mutant genes in homozygous state. It can lead to increase of genetic load in these populations.The most effective method of disease determination is genetic testing, but it is not always possible due to lack of data on mutations that cause these diseases. The mechanism of some diseases is similar to those in humans.The genetic testing of Thoroughbred horses must be held to confirm the absence of mutant alleles of hereditary diseases. An analysis of literature data causes and methods of diagnosis of some inherited disorders of Arabian horses was conducted. Among the wide variety of inherited horses diseases there are those which are characteristic of certain breeds.
Arabian horse is one of the most common breed in the world. World Arabian Horse Organization (WAHO) was one of the first to pay attention to the need of genetic testing of Arabian horses for the presence of some inherited genetic defects. Such inherited diseases are Severe Combined Immunodeficiency Disorder, Lavender foal syndrome, Cerebellar abiotrophy.
Severe combined immunodeficiency is an autosomal recessivedisorder.The genetic basis of the condition is a fivebase-pair deletioninthe gene coding for DNA-dependent protein kinase catalytic subunit (DNAPKcs),located on equine chromosome nine. Affected foals are unable to mount pathogen specific cellular or humoral immuneresponses. These foals may appear clinically normal at birth, butsuccumb to infection as protection from maternal antibodieswanes. Foals are frequently affected by pathogens such asadenovirus and Pneumocystis carinii that rarely cause disease innormal foals.Clinical signs arenoticeable at an average age of four months, though there have been cases where thecondition is first seen shortly after birth and other cases where the onset is gradual andthus clinical signs are first recognized in horses that are more than one year of age.
Lavender foal syndrome, also known as coat colour dilutionlethal, is a disorder of Arabianfoals, particularly those of Egyptian descent. The disorder is inherited by autosomal recessive pattern. Clinical signs include a dilute coatcolour that in some cases can be silver, pink or lavender. Affected foals are subjected to euthanasia. Recent studies have determined the genetic basis of LFS to be a single base-pair deletion in the MYO5Agene, which codes for the protein myosin-Va. The mutation alters thereading frame of MYO5A and results in the incorporation of a premature stop codon.
Cerebellar abiotrophy typically manifests as progressive neurological dysfunction beginning at birth. Clinical signs of CA tell about brain damage and include ataxia, head tremor and hypermetria. Prior to thedevelopment of genetic testing, a preliminary diagnosis of CA was confirmed by post-mortalhistopathological examination of the brain. The cerebellum is characterised by apoptosis of the Purkinje cell layer. A pattern of inheritance consistent with anautosomal recessive trait has been observed, but a causativemutation has not yet been identified.
Timely diagnosis of hereditary diseases of Arab horses will enable to eliminate from the selection process those animals which are carriers of letal genes, and will prevent the accumulation of genetic loadin populations. The most effective method of the determination of hereditary diseases is genetic testing of horses. Determining of the reasons that cause mutations and the development of genetic tests for their diagnosis allows to speed up the healing process of Arabian horse breed from all the inherited diseases mentioned.
Key words: horse, inherited disease, mutation, gene.
1. Kushner, H.F. (1964). Nasledstvennost selskohozjajstvennyh zhivotnyh [Heredity of farm animals]. Moskow: Kolos [In Russian].
2. Baird, J.D. & Mackenzie C.D. (1974). Cerebellar hypoplasia and degeneration in part-Arab horses. Australian Veterinary Journal. 50: 25–28.
3. Felsburg, P.J. [et al.]. (1999). Canine X-linked severe combined immunodeficiency. Veterinary Immunology and Immunopathology. 69: 127–135.
4. Fox, J. [et al.]. (2000). Cerebello-olivary and lateral (accessory) cuneate degeneration in a juvenile American Miniature horse. Veterinary Pathology. – 37: 271–274.
5. Page, P. [et al.]. (2006). Clinical, clinicopathologic, postmortem examination findings and familial history of 3 Arabians with lavender foal syndrome. Journal of Veterinary Internal Medicine. 20: 1491–1494.
6. Pongratz, M.C. [et al.]. (2010). Diagnostic evaluation of a foal with cerebellar abiotrophy using magnetic resonance imaging (MRI). Pferdeheilkunde. 26: 559–662.
7. Fanelli, H.H. (2005). Coat color dilution lethal (“lavender foal syndrome”): A tetany syndrome of Arabian foals. Equine Veterinary Education. 17: 260–263.
8. Gerber, H. (1995). Cerebelläre Abiotrophie bei Vollblutaraber-Fohlen. Pferdeheilkunde. 11: 423–443.
9. Brault, L.S. [et al.]. (2011). Mapping of equine cerebellar abiotrophy to ECA2 and identification of a potential causative mutation affecting expression of MUTYH. Genomics. 97: 121–129.
10. McGuire, T.C. & Poppie M.J. (1973). Hypogammaglobulinemia and thymic hypoplasia in horses: a primary combined immunodeficiency disorder. Infectious Immunology. 8: 272–277.
11. Georgescu, S.E. [et al.]. (2006). Molecular basis and diagnostication of SCID in Arabian Horses. Romanian Biotechnological Letters. 11: 2875–2879.
12. Perryman L.E. Combined immunodeficiency of Arabian horses: confirmation of autosomal recessive mode of inheritance / L.E. Perryman, R.L. Torbeck // Journal of the American Veterinary Medical Association. – 1980. – Vol. 176. –
P. 1250–1251.
13. Perryman L.E. Molecular pathology of severe combined immunodeficiency in mice, horses, and dogs / L.E. Perryman // Veterinary Pathology. – 2004. – Vol. 41. – P. 95–100.
14. Purkinje cell apoptosis in Arabian horses with cerebellar abiotrophy / A. Blanco, R. Moyano, J. Vivo [et al.] // Journal of veterinary medicine. A Physiology, pathology, clinical medicine. – 2006. – Vol. 53. – P. 286–287.
15. Shin E.K. A kinase-negative mutation of DNA-PKcs in equine SCID results in defective coding and signal joint formation / Euy Kyun Shin, Lance E. Perryman, Katheryn Meek K. // Journal of Immunology. – 1997. – Vol. 158. –
P. 3565–3569.
16. Brooks, S.A. [et al.]. (2010). Whole-genome SNP association in the horse: Identification of a deletion in myosin va responsible for Lavender Foal Syndrome. PloS Genet. 6: e1000909.
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