INDUSTRY
All work and play at the Merial CPD Raceday The first in a series of combined seminar and raceday equine performance CPD events was held at York Racecourse in May. Organised by European Trainer Magazine for Merial Animal Health and supported by Bedmax and Haygain, the clinical series included a top lineup of speakers. Dr Rhiannon Morgan MRCVS attended and reports on the latest thinking in equine health. WORDS: DR RHIANNON MORGAN MRCVS PHOTOS: GILES ANDERSON
Jo Gater-Willats: Equine influenza vaccines
Jo Gater-Willats of Merial Equine started off by addressing the question, ‘What do we want from a vaccine?’ The answer: long-lasting protection against equine influenza for the individual horse, ensuring the horse does not suffer from clinical disease and can perform to its optimum ability. Gater-Willats went on to explain that potential immunity gaps can occur, typically between the second and third vaccines, and after this, the level of antibody in the horse can wane over the course of the first year. Unvaccinated animals act as a reservoir for disease and their impact on a potential epidemic is therefore enormous. Reducing the reservoir by vaccinating these horses and reducing the amount of shedding into the environment is critically important. Gater-Willats also emphasised the significance of the virus’s ability to evolve. Virus evolution can result in the vaccine strain being different to the field strain (the strain that the horse may be exposed to). The bigger the difference between these strains, the harder it is for the antibodies stimulated by the vaccine to recognise the virus challenge and be able to respond to it. The equine influenza A virus (H3N8) diverged into two different strains: the European strain (not seen since 2005 on a global scale) and the American strain, which split into the Kentucky (not seen since 2006) and Florida strains; clade 1 and clade 2 sublineages. Florida clade 1 is predominantly seen in the USA, and Florida clade 2 has been the main strain detected in the UK since 2010. “Whilst horses travelling around the world could potentially spread these strains, their global distribution is fairly established and the Florida clade 2 strain is closely monitored by the Animal Health Trust.” Gater-Willats warned that there have, so far, been two outbreaks of equine influenza in the UK during 2016, and historically most 78
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outbreaks have occurred in the last half of the year, so we may see more. The number of outbreaks per year has increased over the last three years, but whether this is due to more frequent testing or to a true increase in outbreaks is unknown.
Rob Pilsworth: Joint pain: What are we treating and why are we treating it?
When a horse suffers from joint pain, the clinical signs very much depend on the underlying pathology occurring within the joint. Some problems occur more commonly at certain ages in the racing thoroughbred and are often affected by training status and the presence of any underlying developmental problems present since birth. Dr Rob Pilsworth of the Newmarket Equine Hospital explained that horses under two years old can suffer from Developmental Orthopaedic Disease manifesting as osteochondrosis dissecans (0CD) complex or subchondral cyst-like lesions (SCLL). OCD lesions result in weak, unstable bone; damaged cartilage; and floating debris, which causes an inflammatory response in the joint and can cause it to become swollen, hot, and painful. When treating these conditions, the main aims are to reduce the inflammatory reaction, restore the joint to normal function, and most importantly, to ensure we preserve the long-term integrity of the joint. Intra-articular medication can temporarily diminish the inflammatory response but the horse may continue to exercise on an unstable joint surface. The underlying problem remains and therefore the inflammation and joint pain will more than likely recur. Surgically removing
the debris and any damaged cartilage flaps, and providing an even surface for some degree of cartilage repair, is Pilsworth’s preferred treatment of choice. It is well known that the mechanical properties of the newly formed cartilage are incomparable to healthy hyaline articular cartilage. However, providing some protection to the underlying subchondral bone, which can be sensitive, and reducing the debris, which is driving the inflammatory process, would be the gold standard. Subchondral cyst-like lesions can occur secondary to OCD lesions or to other causes such as trauma. Treatment of these lesions often depends on the individual patient. Steroids administered either into the entire joint (intra-articular) or directly into the lesion (intra-lesional) are commonly used, accompanied by a period of rest and a controlled-loading rehabilitation programme. At two years old, the demands of racing thoroughbreds rapidly escalate from field turnout to cantering one-to-two furlongs carrying a rider. This increase in exercise intensity, and as such forces through the joint, may be multiplied by the presence of angular limb deformities causing abnormal and uneven loading of the joints. These factors can put substantial strain on all joint components: the fibrous joint capsule, synovial membrane, supporting ligaments, and subchondral bone, resulting in possible capsulitis, synovitis, and/or bone bruising, respectively. These conditions can manifest as hot and effused joints, which are painful to flex and may cause lameness. However, there will be little radiographic evidence. The treatment aims are exactly the same as those when treating younger horses: to reduce the inflammatory response, restore the joint to normal function, and preserve the long-term integrity of the joint. There is usually no loss of cartilage integrity in these conditions and therefore, Pilsworth recommends conservative treatment; reducing exercise