Congenital diseases in horses

Congenital diseases and defects in horses are conditions that are present at birth, usually due to genetics, but sometimes also due to conditions during pregnancy (infections, poor nutrition, toxins).

Below is an overview arranged by body system:

Musculoskeletal System

Angular Limb Deformities (ALD)

Limb deformities – legs curved in/out. Common in foals.

Flexural Deformities (Contracted Tendons)

Excessive bending of joints (e.g. “club foot”).

Dwarfism

Rare, usually genetic, with deformities of limbs and vertebrae.

Nervous System

Cerebellar Abiotrophy (CA)

Atrophy of the cerebellum – lack of coordination, tremors.

Common in Arabs and Quaternaries.

Wobbler Syndrome (CVM)

Compression of the cervical spinal cord → instability.

Hydrocephalus

Accumulation of fluid in the brain – enlarged head.

Ocular System

Microphthalmia

Eyes smaller than normal.

Congenital Cataracts

Congenital clouding of the lens.

Coloboma

Structural defects in parts of the eye.

Cardiovascular System

Ventricular Septal Defect (VSD)

A hole between the ventricles of the heart – can cause exercise intolerance.

Patent Ductus Arteriosus (PDA)

A fetal blood vessel that does not close after birth.

Respiratory System

Choanal Atresia

Congenital obstruction of the nasal passages – an emergency in foals.

Cleft Palate

Cleft palate – causes food aspiration.

Digestive System

Atresia Ani / Coli

Lack of anal opening or missing parts of intestine.

Meconium Retention

Primary fecal retention (not always genetic but congenital).

Reproductive System

Cryptorchidism

Descended testicle – common, has a genetic component.

Intersex Conditions

Rare – disorders of sexual development.

Known Genetic Diseases

SCID (Severe Combined Immunodeficiency)

Severe combined immunodeficiency – fatal without treatment.

Common in Arabians.

HYPP

Potassium channel disorder – attacks of weakness.

Common in Quaternaries.

GBED

Glycogen storage disorder – fatal in foals.

HERDA

Skin defect – delicate skin that tears easily.

Main risk factors

   •   Breeding within the same bloodline

   •   Nutritional imbalance during pregnancy

   •   Exposure to toxins / medications

   •   Viral infections in the fetus

Prevention and recommendations

   •  Genetic testing for parents before breeding

   •  Balanced nutrition for the pregnant mare

   •  Avoidance of genetic inbreeding

   •   Preliminary veterinary examination for the foal

*It is always advisable to consult a qualified veterinarian.