Arabian Horse Diseases

How can one not look at the beauty, majesty and proud bearing of the Arabian Horse? In any situation they are eye-catching with their statuesque refinement, bringing many a horse lover flocking to watch and admire this beautiful breed. Unfortunately, lurking under that exquisite exterior there are known genetic conditions.

One thing about genetic diseases and disorders, they are not bias and every breed of horse, dog, mammal for that matter, has its own related problems.

In this instance, the Arabian Horse, there are six known disorders at this stage, this is not to say that more will not come to light as years of breeding progress. Unfortunately some of these disorders are lethal with foals either not making full term or having to be euthanised within days or weeks of birth. In some instances foals die from what appears to be natural causes at any age but upon closer examination there is an underlying cause, possibly one of these disorders.

SCID – Severe Combined Immunodeficiency Disorder: Foal that are born with this disorder have a severely weakened immune system, thus their natural defence system against infections is compromised. These foals generally die by five months of age from an infection such as pneumonia, or it is necessary to euthanise them due to lack of response to medical treatment.

It is already known that SCID is an autosomal (not sex related) recessive trait, basically meaning that both parents must be carriers for an affected foal to be produced. There is a DNA test available for this disorder that can tell you if a mare or stallion is a carrier, and the best advise is not to breed carrier to carrier, as genetically the general rule of an SCID foal being produced is 1 in 4.

LFS – Lavender Foal Syndrome CCDL – Coat Colour Dilution Lethal: These foals are born with a diluted coat colour described as lavender, silver, pewter or even pinkish. Many of these foals are born from a difficult labour, are unable to stand at birth, are positioned with head and neck drawn back and generally have seizures or paddling movement. They are unable to erect themselves but do have excellent suck reflex, so can be bottle fed. LFS is a neurological disorder associated with brain lesions. There is testing being performed at present to determine as to whether this disorder is genetic.

JES – Juvenile Epilepsy Syndrome: Also known as “benign” epilepsy or “idiopathic” epilepsy, this condition is not usually fatal but it can be disabling with suggestions of a genetic link to LFS being made. Foal appear normal at birth but periodically they will have epileptic seizures, anywhere up to six months of age. Extremely severe seizures can cause the foal to loose consciousness, with the eyes rolling back into the head. Traditional anti-seizure treatment will reduce the severity of the symptoms and on the whole affected foals will outgrow this condition at 12 to 18 months of age. It is unclear as to the mode of inheritance for this disorder but it has been suggested that multiple genes may be involved.

CA – Cerebellar Abiotrophy: First signs are a lack of coordination with the degree of severity differing between individuals. This lack of coordination is caused by the Purkinje cells in the brain’s cerebellum beginning to die. Affected foals are generally born without any symptoms but as they grow, the degeneration of the brain cells begin. Head tremors, lack of coordination and an inability to gauge distance are among the signs of this disorder. CA has often been misdiagnosed as Wobblers Syndrome but WS is caused by compression of the spinal cord and can be correctly diagnosed through radiographs. Unfortunately, CA affected foals are euthanised prior to adulthood, as they present a hazard to themselves and to others. There is currently extensive research being done into this disorder trying to identify the defective gene and hopefully they will be able to create a DNA test.

OAAM – Occipito-Atlanto-Axial Malformation: This condition is where the cervical vertebrae fuse together in the neck and the base of the skull, causing compression and injury to the spinal cord. Affected foals are unable to stand and nurse unaided, or the condition may not be noticeable for weeks after birth. Mild uncoordination or paralysis of both front and rear legs should be associated with this condition, and when suspected a radiograph will assist with diagnosis. An indirect DNA test is available for this disorder.

GPT – Guttural Pouch Tympany: Affected foals are born with an abnormal inflation with air, of one or both guttural pouches that are located in the caudal portion of the head. Air is trapped within these pouches and is unable to escape. This swelling is not painful but breathing can be extremely noisy in severely affected animals due to compression of the larynx and pharynx. Swallowing problems are evident, as is discharging of milk and/or fodder from the nostrils. This condition occurs in horses ranging from birth to yearlings and is generally more prevalent in fillies than colts. Surgery can correct the malformation and foals that are thus treated can mature to have fully functional lives. The exact cause of this condition is unknown at this stage and is not specialised to Arabian Horses but rather it affects many different breeds.

In conclusion, I would like to stress that all of the above disorders are fairly rare and to the best of my knowledge I have never had a foal born that was affected by any of the above in 20 years. Unfortunately, this is not to say that I never will, but hopefully with selective and careful breeding, the odds will be kept low.