Interleukin-1 Receptor Antagonist Protein (IRAP) is a new and effective intra-articular treatment for joint disease marketed by Arthrex VetSystems in the USA.  The product was originally developed in Europe, and has been used extensively in Germany.  IRAP is an anti-inflammatory protein that counteracts the destructive effects of inflammatory proteins such as Interleukin-1 (IL-1) that are produced within inflamed or arthritic joints.  The IRAP system has been designed to stimulate the horses’ own white blood cells to produce anti-inflammatory mediators and enzymes, specifically Interleukin 1 receptor antagonist protein (IRAP), which can reduce the inflammation present as a result of degenerative joint disease.  Treatment with IRAP utilizes progressive gene therapy to combat osteoarthritis in your horse.

The process of harvesting IRAP is quite simple and can be performed as an outpatient and/or potentially on the farm.  Blood is collected from the jugular vein and incubated for 24 hours in special syringes that contain glass beads that induce the white blood cells present in the blood to produce and secrete therapeutic proteins, namely, IRAP.

After 24 hours the blood is centrifuged and the serum is separated from the red blood cells. The protein rich serum is then split into 3-6ml doses and the separate doses are frozen for use at a later date.

Typically each collection produces enough serum for between 3-5 injections. It is important to note that the injections are only suitable to treat the horse from which the original blood was collected. The injections can be stored for up to 12 months from the date of collection.

Degenerative joint disease is one of the biggest causes of poor performance and a decreased competitive lifespan in the horse. This is true for all types of equine athletes, from racehorses to dressage and show jumping horses. Both young and old horses can be affected by degenerative joint disease resulting in a loss of athletic ability and possible early retirement.

When injected into a joint, the IRAP protein rich serum stimulates a response from cartilage cells, through a process of cell division and increased cell recruitment. This is actually what sets IRAP apart from other intra-articular treatments for joint disease. The fact that IRAP stimulates cartilage cells means that it has a disease modifying component as well as an anti-inflammatory component. The serum also contains cytokines that act to reduce inflammation within the joint. In addition there are other anti-inflammatory proteins produced during the incubation process that work synergistically with the cytokines to further reduce the inflammation within the diseased joint.

What does the treatment with IRAP involve?

The therapy involves three joint injections at 7-14 day intervals. Most positive effects are seen after the second and the third treatment. The majority of horses will be sound after the third injection. In our hands, more than 90% of horses have returned to soundness after IRAP therapy. After injection, we routinely bandage the joint if possible for 2 days, and the horse should be kept on 3 days of strict stall rest, followed by a period of of hand-walking (30-45 minutes).  Once the course of injections and the final hand-walking period is completed, horses should receive one week of ridden walk exercise, followed by one week of ridden walk and trot, before returning gradually to regular training programs*.

*It is important to note that the instructions may vary, depending on the primary joint disease.

Obviously, as with any joint injection, the joint should be monitored carefully for any signs of infection (heat, swelling, and increase in lameness) – if you notice any of these signs, please contact us.

Once the horse is sound, the horse can resume normal work. If lameness returns after a period of time, any remaining frozen samples can be defrosted and the injections repeated. Often a single injection will suffice at this point and it is unusual for most horses to need to repeat the full course of three injections. However, individual cases can vary and each case will need to be reassessed by your veterinarian if lameness returns.

What cases warrant the use of IRAP?

The cases that generally respond the best to IRAP therapy are those with mild to moderate radiographic signs of degenerative joint disease where the lameness has been localized to a particular joint or joints.

Indications for use of IRAP in the joint include horses with a well defined synovitis/capsulitis, particularly those horses that do not respond well to conventional anti-inflammatory joint medication and horses that have had arthroscopic surgery and have been found to have focal cartilage diseases.

IRAP is NOT recommended for use in tendon sheaths or bursae, in joints where there are bone fragments, fractures, meniscal or ligamentous injury unless it has been successfully treated arthroscopically, in bone cysts, or in horses with advanced osteoarthritis (low success rate).

IRAP is very useful after arthroscopic removal of any chip fragments. In these cases the anti-inflammatory cytokines and proteins reduce inflammation within the joint and encourage a regeneration response from the damaged cartilage. In post surgical cases, we recommend administering the first IRAP treatment between 4 and 10 days after surgery. We recommend that post surgical cases receive the full course of three injections at one week intervals.

Why use IRAP?

IRAP is different from other products because it treats the cause of joint disease and its action is aimed at restoring joint lining and cartilage function. Studies performed in Colorado State University show that treated horses demonstrate reduced lameness, improved joint histology (cellular make up) and a tendency towards cartilage preservation. Our clinic has seen resolution of lameness, a general improvement in the range of motion of the joint and a decrease in joint effusion in treated horses.

Traditionally the most common intra-articular medication for the management of joint disease has been cortisone injections. Clinically, with cortisone injections we often see a sudden response and improvement in the degree of lameness that then gradually wears off over a period of time (6-12 months). When cortisone injections are repeated we often see a decrease in the interval between treatments. Meaning, that the more cortisone injections a horse has into a particular joint, the shorter the duration of therapeutic effect and the sooner that joint will need to be treated again. The use of IRAP often allows us to delay the use of cortisone injections and prolong the athletic life of the horse. In many cases where there has been a very good response to IRAP therapy, cortisone injections to manage the degenerative joint disease can be delayed indefinitely.

Another advantage to using IRAP therapy, is that it does not have some of the same side effects as cortisone. The use of IRAP therapy does not increase the risk of laminitis and there is a smaller risk of joint infection using IRAP compared with using cortisone. Adverse effects of this product have not been reported after extensive use in people and horses in Europe. There have been a few reported cases of reaction to IRAP serum with a ‘flare’ response seen within 24hrs of injection. This is an uncommon side effect that subsides after administration of systemic corticosteroids and application of ice to the joint.

IRAP is another therapy to be added to the battery of tools that we have to combat osteoarthritis in your horse. The reason IRAP is so exciting is its’ potential for a long-term effect on battling osteoarthritis. Whereas some of the therapies listed above might only have short-term effect, IRAP has the potential to stop the cartilage matrix from being degraded and increase healing. IRAP has the ability to stop the inflammation cycle and bring comfort to your horse. The research on IRAP is ongoing but the results have been very encouraging.

Typical cost:

Please contact our office for pricing information:

781-585-2611, [email protected], or click here

IRAP harvesting and preparation is usually performed as an outpatient service of South Shore Equine Clinic, as processing of the blood should occur as soon as possible from the time of blood draw. In special circumstances it has been performed stall side.

Please contact us if you are interested in learning more about IRAP or if you think your horse is a candidate for IRAP therapy!