Infectious Disease | ID Perspective

The Importance of Serum Amyloid A (SAA) Testing in Foals

By Jacquelin Boggs, DVM, MS, DACVIM

Foaling season is an exciting and busy time for veterinarians! Outlined below are some quick tips as to why you should make Serum Amyloid A (SAA) testing a priority during foal exams.

GENERAL USE
Fortunately, most foals arrive without complications. Yet in nearly every case, measuring SAA levels in mares and newborns is a helpful diagnostic metric to know. Make sure to pack the Stablelab® EQ-1 Handheld Reader on the way to mare and foal check-up appointments, and especially when called out on emergency so that you can make quick, informed decisions on the spot.

• In foals, an SAA level >50 μg/mL is suspicious for early onset of infection and should be retested in 12 to 24 hours to see whether it is rising or falling1
• When SAA is >100 μg/mL, this is indicative of infection1
• Incorporating SAA into routine screening exams for R. equi has been shown to reduce antibiotic treatment by more than 45% without negatively impacting foal health2

Stablelab provides results within 10 minutes at the farm, with no need to wait for samples to be shipped or lab results to be turned around.

NEWBORN FOAL EXAM
It’s easy to incorporate SAA testing into your newborn foal exam in addition to checking immunoglobulin G (IgG). These two diagnostics can be performed stall-side during your exam. Each test only requires a small amount of blood that can be taken from the same syringe and provides you with very different information as to the health status of the foal.

• While IgG measures maternal antibody transfer from mare’s colostrum, it is important to note that IgG does not specifically correlate with the overall health of the foal.
• However, SAA is a biomarker of inflammation caused by infection and does correlate with health.
• If SAA is elevated, diagnosis and treatment are critical to get on top of quickly
• In foals, the normal value is <100 μg/mL. Anything greater suggests infection and would signal you to hunt for an inciting cause and start treatment
• •Additionally, SAA is 30 times more sensitive than body temperature, suggesting you can detect abnormalities sooner, which is especially important in this critical window of the newborn foal’s life3
  Incorporating Stablelab into your new foal exams along with IgG can be useful to catching infection early, beginning treatment faster and supporting recovery.

EXPLAINING THE DIFFERENCE BETWEEN SAA AND IGG TO CLIENTS
A simple way to explain Stablelab testing to clients is that SAA is a biomarker that measures systemic inflammation caused by infection and correlates with the real time health status of the foal. If SAA is elevated, additional diagnostics should be performed to find the cause and treatment started quickly.

SAA can also be used throughout the course of treatment to check the response to therapy until it comes back down to normal. IgG measures the transfer of maternal antibodies to the foal, to bridge immunity to certain diseases until the foal is able to produce their own. It does not correlate to the current overall health of the foal.

REFERENCES
1. Stoneham SJ, Palmer L, Cash R, et al. Measurement of serum amyloid A in the neonatal foal using latex agglutination immunoturbidimetric assay: determination of the normal range, variation with age and response to disease. Equine Vet J. 2001;33(6):599-603.
2. McCracken JL. Evaluation of white blood cell, fibrinogen, serum amyloid A, and ultrasonograph­ic grade to refine a R. equi screening program. AAEP Proceedings. 2019;65:522-530.
3. Oertly M, Gerber V, Anhold H, et al. The accuracy of serum amyloid A in determining early inflammation in horses following long-distance transportation by air. AAEP Proceedings. 2017:460-461.

For more information, visit the Stablelab website.