Glycogen Branching Enzyme Deficiency (GBED)

This disease is life-threatening and should be treated by a veterinarian swiftly.

Glycogen is an important energy source for tissue within the body, and is vital for maintaining normal glucose levels in the body and for growth in the developing foetus and neonate. In horses affected with glycogen branching enzyme deficiency, a genetic mutation impairs the functioning of an enzyme (glycogen branching enzyme) resulting in the faulty synthesis of glycogen. Muscles cannot store or mobilise glucose in the form of glycogen, and tissues are unable to maintain normal glucose homeostasis. Without appropriate storage of ingested glucose, the animal cannot maintain adequate levels of glucose to keep organs working effectively.

Hypoglycaemic episodes, where the blood glucose level falls below normal can cause confusion, uncoordinated movement and weakness and may cause loss of consciousness, cardiac arrest and sudden death.

Glycogen branching enzyme deficiency is an inherited disease that leads to stillbirths and spontaneous abortions.
Foals that survive to parturition become progressively weaker and most do not survive longer than a few months.

Symptoms

Exclusive in

Treatment

There is no treatment for GBED. Early recognition and euthanasia can save considerable expense for owners of foals in neonatal intensive-care units. It is important that veterinarians and breeders recognize that GBED may present both as foals born alive that subsequently succumb to GBED as well as abortion.

Prevention

A DNA test is available to detect the gene mutation responsible for glycogen branching enzyme deficiency. It will identify horses that are homozygous affected, heterozygous carriers or unaffected (normal).