Irap: A new approach to treat arthritis in the horse

Lameness resulting from joint degeneration or osteoarthritis is one of the most prevalent diseases affecting horses. Osteoarthritis involves inflammation of the joint lining and progressive destruction of articular cartilage that covers the ends of the bones composing a joint. The progressive cartilage destruction decreases the natural shock absorbing function and range of motion of the joint, ultimately resulting in lameness. Joint cartilage destruction is caused by a number of substances that increase when inflammation occurs in the joint. Laboratory and clinical research has shown that one of the main substances responsible for cartilage destruction is interleukin 1 (IL-1). A multitude of research has also shown that antibodies produced against this cartilage destructive substance (IL-1) have a beneficial effect in arresting cartilage damage (Figure 1).

Figure 1:  A fetlock joint with advanced arthritis

Figure 2:  A normal healthy fetlock joint

Traditional treatments for osteoarthritis include reduced/altered exercise, bandaging, anti-inflammatory agents (e.g. Bute), anti-arthritic drugs such as Adequan, artificial joint fluid such as Hyaluronan and corticosteroids. For many years these treatments have and continue to improve the condition of horse’s joints and subsequently help maintain soundness of horses. Despite this, current treatments have limitations in their effectiveness and some are associated with side effects.

Recently a treatment technique has been developed in Europe which is targeted specifically at the cartilage destructive IL-1. The treatment process uses autologous conditioned serum (ACS) that contains antibodies against IL-1 produced by the horses’ own blood.  The process of creating ACS involves taking blood, from the particular horse requiring treatment, in a special syringe system (irapÒ). This blood filled syringe is then incubated for 24 hours, which results in extremely high levels of the naturally occurring antibody against IL-1 (interleukin-1 receptor antagonist protein (IRAP)) being produced. After 24 hours antibody levels have been shown to increase up to 140 fold in the serum of the blood. The syringe is then spun in a centrifuge to separate the red blood cells from the serum to allow harvesting of the serum component of blood in a syringe (Figure 3). A portion of the antibody-rich serum is injected into the osteoarthritic joint that day and the remaining serum is stored in a freezer for further treatments. Typically 3 treatments are recommended for optimum clinical effect whilst the horse remains in training or is rested. Treatment of osteoarthritic joints with ACS has been used in people since 1998.

Figure 3: IRAP being injected into a carpal joint at Clyde Vet Group

Figure 4:  ACS being filtered before joint injection

The ability to use the horses' own blood to combat the signs of arthritis (pain, inflammation and reduced joint range of motion) has many advantages. A principal advantage is that the mechanism of action of this treatment is that it addresses the very cause of arthritis, at the cartilage and joint lining level.

Clyde Vet Group Equine Hospital installed the irap® facility at Lanark in October 2007. 


The material contained in this website is presented for information purposes only . The material is in no way intended to replace professional veterinary care or attention from a professional veterinary surgeon. 

The advice given in any of our web pages cannot be used as the basis for a diagnosis or choice of treatment.

Clyde Vet Group advises that you should always consult a veterinary surgeon about any queries with animals under your care.

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