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A New Way to Diagnose Joint Infection in HorsesBy Kentucky Equine Research Staff · September 13, 2017

Heat, swelling, and profound lameness stemming from a joint should always raise alarm bells in a horse owner’s mind, prompting a call to the veterinarian. With any luck, it is not a joint infection, but how can you find out for certain? According to a recent study by British researchers*, measuring serum amyloid A (SAA) values in blood can help diagnose joint infections so early treatment may improve outcomes.

“SAA is classified as an acute-phase protein produced by the liver in response to inflammation. Within a mere six hours of an inflammatory insult, SAA levels increase dramatically, helping veterinarians diagnose a variety of conditions, including joint infections,” explained Kathleen Crandell, Ph.D., an equine nutritionist for Kentucky Equine Research (KER).

Because joint infections, also known as synovial sepsis, can be life threatening, achieving an accurate diagnosis early in the course of disease is needed. In some cases, distinguishing a joint infection from other joint issues, such as osteoarthritis, intra-articular fracture and nonseptic tenosynovitis, can be tricky.

Traditional methods of diagnosing joint infections include culturing synovial fluid to identify bacteria; directly visualizing bacteria in synovial fluid when smeared on a microscope slide; and measuring nucleated cell counts, infection-fighting neutrophils, and protein in synovial fluid (increases in each of these suggests infection). Unfortunately, none of these tests are perfect and better strategies are needed.

To determine if SAA could help differentiate infection from noninfectious joint diseases, SAA was measured in blood and synovial fluid samples collected from 112 horses—38 with synovial infection, 66 with nonseptic intrasynovial pathology [NSISP], and 8 healthy controls. Key findings of the study were:

  • Blood and synovial fluid SAA were significantly higher in horses with joint infections than in NSISP and control horses;
  • SAA values were similar in NSISP and control horses; and
  • Both blood and synovial fluid SAA had good sensitivity and specificity, meaning that they were sufficiently able to diagnose horses with joint infections when present and rule out joint infections when they were not.

“This study shows that blood and synovial fluid SAA concentrations can help distinguish joint infections from nonseptic synovial pathology,” concluded the researchers.

“From a nutritional perspective, joint supplements not only help horses already diagnosed with joint diseases such as osteoarthritis, but they also protect joints before an infection or injury occurs,” reminded Crandell.

She added, “KER offers several joint supplements that support joints when offered prophylactically, prior to the onset of trauma or injury. Look for KER•Flex, which contains high-quality glucosamine HCl and chondroitin sulfate; Synovate HA, a high molecular weight sodium hyaluronate liquid that helps maintain proper joint health and lubricates joints for frictionless motion, especially in high-motion joints; and the omega-3 fatty acid supplement, EO•3.”

Australian horse owners should look for these research-proven products.

*Robinson, C.S., E.R. Singer, M. Piviani, et al. Are serum amyloid A or D-lactate useful to diagnose synovial contamination or sepsis in horses? Veterinary Record. In press.