So Marc Oertly, DVM, of the Swiss Institute of Equine Medicine, in Berne, set out to determine whether serum amyloid A (SAA) concentrations could suggest inflammation sooner than a rectal thermometer in traveling horses. He presented his results at the 2017 American Association of Equine Practitioners Convention, held Nov. 17-21 in San Antonio, Texas.
Serum amyloid A is a protein present in undetectable to low levels in healthy horses. In response to inflammation, the liver releases SAA into the bloodstream, causing levels to rise 1,000-fold or more. Veterinarians can measure these levels to detect infection and monitor treatment response.
In a study funded by StableLab, a company that developed a stall-side blood test to measure SAA in horses, Oertly evaluated the optimum time point for measuring SAA after horses travel. He followed 121 high-level Warmblood show jumpers, ranging in age from 8 to 17, along three stops of the Longines Global Champions Tour.
All horses first flew to Miami, Florida, and veterinarians conducted a stall-side SAA reading and health check prior to the flight, upon arrival to quarantine, 24 hours after arrival, and 48 hours after arrival. Veterinary staff took rectal temperatures twice daily. Then horses flew to Mexico City and Shanghai, where Oertly repeated this process.
Of these horses, 31 developed clinical signs of a problem (e.g., coughing). While all 31 had elevated SAA levels, only one had a high temperature. The sick horses’ SAA levels were above 35 μg/mL 24 to 48 hours before they started showing clinical signs, particularly in cases of respiratory disease.
“There was a significant difference in SAA levels between healthy and sick horses,” said Oertly. “SAA has a much higher sensitivity than rectal temperature.”
At 24 hours after horses’ arrival, SAA had 86.7% sensitivity (ability to identify a sick horse correctly) and 91.9% specificity (ability to identify a healthy horse correctly), compared to 3.2% sensitivity and 100% specificity with rectal temperature.
“SAA should be added to the physical exam as standard protocol to evaluate health in high-risk horses,” said Oertly. “If I detect a horse as early as possible, I might have time to treat the horse to still perform at the highest level.”
So, he said, SAA is a more reliable indicator of inflammation than rectal temperature in traveling horses, and the ideal time to perform an SAA reading is 24 hours post-arrival, using a 35 μg/mL threshold. Of course, additional diagnostics are warranted if a horse’s SAA levels rise.