Texas Equine Veterinary Association

www.texasequineva.com • 15 from the Department of Medicine and Epidemiology at the University of California, Davis, School of Veterinary Medicine, determined that SAA helps differentiate between infectious and non-infectious respiratory disease. In this study, SAA levels were determined in 207 horses. Those horses were diagnosed with one of the following—influenza (42), equine herpesvirus-4 (43), IAD (38), S. equi ss equi (44)—or served as healthy controls (40). The key findings were as follows. All three groups of horses diagnosed with an infectious respiratory condition had SAA levels significantly higher than the healthy control horses, including the IAD group. The non-infectious IAD and control groups had significantly lower SAA values than each of the three groups with infectious respiratory disease. Due to overlapping values, in this study, SAA levels alone could not be used to distinguish between bacterial and viral respiratory diseases requiring other diagnostic tests must be conducted on nasal secretions, such as culture or polymerase chain reaction. Precompetitive testing of SAA to determine if a horse has a subclinical disease despite having no cough or fever with a history of poor performance can be extremely helpful. In some cases, walled-off abscesses in lungs that can't easily be detected by other methods may be found. TRANSPORTATION SAA is a more reliable indicator of inflammation caused by infection than rectal temperature in traveling horses. (5) Measuring SAA can also be used in apparently healthy horses prior to transport, competition, or surgery to ensure the health of their respiratory tracts for maximal health and performance. Horses that travel by air or land are at a particularly high risk of being exposed to infectious disease—from commingling with other horses as well as the increased stress on their immune systems, lowering their ability to fight off infection. The sooner you can identify a sick horse to begin treatment, the better for all involved. In a prospective study performed by Dr. Marc Oertly of the Swiss Institute of Equine Medicine (5) , he evaluated the optimum time point for measuring SAA after horse's travel. He followed 121 high-level Warmblood show jumpers, ranging in age from 8 to 17, along three stops of the Longines Global Champions Tour. It was hypothesized that SAA concentrations could suggest inflammation sooner than a rectal thermometer. All horses first flew to Miami, Florida, and veterinarians conducted a stall-side SAA reading and health check prior to the flight, upon arrival to quarantine, 24 hours after arrival, and 48 hours after arrival. Veterinary staff took rectal temperatures twice daily. Then the horses flew to Mexico City and Shanghai, where Oertly repeated this process. Of these horses, 31 developed clinical signs of a problem (e.g., coughing). While all 31 had elevated SAA levels, only one had a high temperature. The sick horses' SAA levels were above 35 μg/mL 24 to 48 hours before they started showing clinical signs, particularly in cases of respiratory disease. There was a significant difference in SAA levels between healthy and sick horses and SAA was 30x more sensitive than rectal temperature in differentiating between the two. The ideal time to perform an SAA reading is 24 hours post-arrival, using a 35 μg/mL threshold. Of course, additional diagnostics are warranted if a horse's SAA levels rise. MUSCULOSKELETAL CONDITIONS SAA levels will not elevate unless there is an infectious component In general, SAA levels remain negligible in the face of inflammation without infection (e.g., training-related strains to tendons or ligaments, fractures, etc.); infections cause much more profound SAA increases. (1, 2) For example, a simple long bone fracture, SAA should not rise following surgery to repair if there is no infection. Monitoring that same horse after surgical repair of the fracture could reveal infection (e.g., from the implants used or surgical site contamination). With cellulitis, SAA levels will not elevate unless there is an infectious component. Where SAA may come in handy is for detecting conditions such as joint infections (septic arthritis) following administration of intra- articular medications or puncture of a synovial structure. GASTROINTESTINAL TRACT DISEASE SAA is useful in detecting infectious causes of colic such as: peritonitis, enteritis or colitis With the current literature available at the time of publication 1 , measurement of SAA is not useful to determine surgical from medical colic. However, SAA can indicate whether a horse is fighting an infection postoperatively and should be used to identify problems early. SAA is also useful in infectious cases of colic such as peritonitis, enteritis, or colitis. ASSESSING FOAL HEALTH Incorporate SAA as part of your newborn foal examination Breeders often use immunoglobulin G (IgG) to measure a foal's

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