No one test can reliably diagnose septicemia (systemic infection) in a foal. The clinician must wait for the results of blood cultures, which can take days. However, preliminary studies of a blood protein called serum amyloid A (SAA) have shown it to rapidly increase in response to inflammatory diseases. Until now, fibrinogen (soluble plasma protein) has been used as an early indicator of inflammation, along with increasing or decreasing white blood cell (WBC) counts (increased WBC counts indicate immune response to infection). This study, from the veterinary teaching hospital in Uppsala, Sweden, was designed to compare SAA with fibrinogen and WBCs in very young foals as a diagnostic tool for identifying sepsis.

Twenty-five foals were admitted during the study period. Blood was collected for culture as well as measurement of SAA, fibrinogen, and WBC analysis. Results indicated that foals with positive culture results (septicemia) also had significantly increased SAA with inconsistently increased fibrinogen and WBCs. Foals with negative blood cultures had normal SAA and fibrinogen with inconsistent changes in WBCs. When blood cultures were ambiguous, which can indicate very early sepsis, SAA was moderately to markedly increased, while fibrinogen and WBCs were typically normal. Finally, foals diagnosed with Rhodococcal pneumonia had increased fibrinogen and WBCs even after treatment, while SAA decreased steadily during treatment and was normal after treatment.

These results led the authors to conclude that SAA could be a useful diagnostic tool for predicting sepsis in foals prior to blood culture results, and could also be useful to monitor progression of therapy in foals with Rhodococcus pneumonia.

Hultèn, C.; Demmers, S. Equine Veterinary Journal, 34 (7), 693-698, 2002