In the early stages of infection or inflammation, it might be apparent that something isn’t quite right with your horse, but for all intents and purposes, he’s clinically normal—perhaps no fever, normal appetite. Such vague signs can delay diagnostic and treatment decisions, as the veterinarian opts for a “wait-and-see” approach, leaning on serial blood tests for clues.

Fortunately, an accurate and reliable indicator for infection is gaining traction in equine practice: serum amyloid A (SAA) concentration. Rose Nolen-Walston, DVM, Dipl. ACVIM, associate professor of large animal internal medicine at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center, described its uses during the 2015 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas.

Nolen-Walston explained that SAA is an inflammatory marker that the liver produces as part of the body’s response to inflammation. Veterinarians can use it to differentiate between horses with systemic inflammation and those that have noninflammatory diseases.

Historically, veterinarians have relied primarily on another inflammatory marker, the protein fibrinogen, to identify infections in horses. All horses have a baseline level of fibrinogen in their bloodstream that rises slightly with inflammation. In contrast, SAA isn’t present without inflammation, but levels rise into the thousands when significant infection sets in, Nolen-Walston said. Additionally, SAA levels rise and normalize much faster than