Occipitoatlantoaxial malformation / OAAM (HOXD3-related) - Horse

What does this test examine?

This genetic test examines a 2.7 kb deletion near HOXD3 in horses. The condition is known as occipitoatlantoaxial malformation, OAAM, atlanto-occipital fusion and congenital craniocervical vertebral malformation.

What does this mean for the foal?

OAAM disrupts normal development of the junction between skull, atlas and axis. Affected foals may show abnormal head and neck posture, progressive ataxia, reduced neck flexibility, tetraparesis or paralysis from birth. Some foals are stillborn or severely neurologically affected soon after birth.

Not every form of OAAM is explained by this single deletion. This test is therefore intended to identify or exclude the described HOXD3-region deletion in Arabian lines.

Practical value of this test

• The test helps distinguish clear horses, carriers and foals with two copies of the tested deletion.
• Breeders can avoid carrier-to-carrier matings.
• In a foal with compatible clinical signs, the result provides focused genetic information about this OAAM form.

Inheritance

The tested OAAM deletion is inherited as an autosomal recessive trait. Carriers have one copy and can pass the deletion on; foals with two copies have a high genetic risk for the described OAAM form.