Acute Phase Protein Dynamics in Equine Health

The acute phase response in horses is a rapid, systemic reaction to tissue injury, infection, exercise or stress, characterised by changes in the concentrations of specific plasma proteins. Key acute phase proteins (APPs) such as serum amyloid A (SAA), C-reactive protein (CRP), haptoglobin and fibrinogen are synthesised predominantly in the liver under the influence of pro-inflammatory cytokines. In healthy equines, baseline levels of APPs are low; rises in these proteins provide sensitive indicators of inflammation before overt clinical signs emerge. The kinetics of SAA are of particular interest: concentrations may increase several hundredfold within hours, then decline rapidly as resolution ensues. Monitoring APP dynamics informs clinical decision-making in a range of contexts—infectious disease surveillance, postoperative recovery, musculoskeletal injury assessment and athletic performance. Advances in immunoturbidometric and point-of-care assays have rendered APP measurement more accessible to field veterinarians, enabling timely detection of subclinical disease, differentiation between inflammatory and non-inflammatory conditions, and evaluation of therapeutic efficacy. Global economic impacts—through reduced morbidity, optimised treatment regimes and improved animal welfare—underscore the importance of standardised assays and reference intervals. Current research seeks to refine assay accuracy, elucidate species-specific kinetics and integrate APP profiling into routine health monitoring of sport horses, breeding stock and equids in low-resource settings.

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Acute Phase Protein Dynamics in Equine Health publication trend

The graph below shows the total number of articles in acute phase protein dynamics in equine health across all publications each year (not limited to Nature Index journals).

Technical terms

Acute phase protein: A plasma protein whose concentration increases or decreases by at least 25% during systemic inflammation.

Serum amyloid A (SAA): A major equine acute phase protein produced by the liver, rising rapidly in response to inflammation.

Immunoturbidometric assay: A laboratory technique that quantifies proteins by measuring the turbidity generated when antigen–antibody complexes form.

Point-of-care assay: A diagnostic test performed at the site of patient care, providing rapid results without the need for central laboratory facilities.

Hook effect: A phenomenon in immunoassays whereby very high analyte concentrations lead to falsely low readings due to saturation of both capture and detection antibodies.

References

1. Validation of an equine serum amyloid A assay with an unusually broad working range. BMC Veterinary Research (2019).
2. Comparison of a point-of-care serum amyloid A analyzer frequently used in equine practice with 2 turbidimetric immunoassays used in human and veterinary medicine. Journal of Veterinary Diagnostic Investigation (2021).
3. Evaluation of an in-clinic Serum Amyloid A (SAA) assay and assessment of the effects of storage on SAA samples. Acta Veterinaria Scandinavica (2010).
4. The Effect of Different Types of Musculoskeletal Injuries on Blood Concentration of Serum Amyloid A in Thoroughbred Racehorses. PLOS ONE (2015).