A simple saliva test for an enzyme shows promise in identifying horse with colic pain, according to researchers in Spain.
Acute abdominal disease – colics – are among the most important and relatively frequent problems found in horses.
Colics are associated with different degrees of pain, an important part of a veterinarian’s assessment of the issues. Different scales have been developed for clinical use to evaluate the pain in acute abdominal disease in horses.
Jose Joaquín Cerón and his colleagues set out in their pilot study to evaluate salivary alpha-amylase (sAA) and salivary cortisol as potential biomarkers for horses with colic-related pain.
Salivary alpha-amylase is considered a non-invasive biomarker for sympathetic nervous system activity and cortisol is a well-recognised stress hormone.
Both biomarkers were analyzed in a group of horses with acute colics and were compared with a group of healthy control horses.
Biomarker levels were related back to the score for each unwell horse using the five-point Equine Acute Abdominal Pain scale (which ranges from depression and flank-watching to complete collapse), as well as each animal’s heart rate, respiratory rate and plasma lactate levels.
A total of 30 horses were included in the study, 19 with acute abdominal disease diagnosed as either large colon displacements, simple impactions of the colonic pelvic flexure, spasmodic colics or enteritis. The colic cases were reported to have lasted less than a day, although two of them proved fatal.
The other 11 horses were assessed as healthy.
Salivary alpha-amylase was significantly higher – a median 24.5-fold increase – in horses with acute abdominal problems when compared to the healthy horses. Salivary cortisol levels were also found to be higher in the unwell horses.
Neither salivary alpha-amylase nor salivary cortisol correlated with heart rate, respiration rate, plasma lactate levels or Serum amyloid A, a protein which increases in cases of inflammation.
The University of Murcia research team said that although it was a preliminary study, alpha-amylase measurements in saliva could be a useful biomarker of pain-induced stress in horses with acute abdominal disease.
The jump in salivary alpha-amylase was significant.
Salivary cortisol did not correlate with pain scales in this preliminary study, although horses with colic did have higher cortisol values than the healthy ones.
However, it was worth examining salivary alpha-amylase levels as a prognostic factor, since the highest values were found in the two horses in the study who did not survive their colic, the researches said.
A larger study using more horses could also assess possible differences in the biomarkers depending on the origin of the acute abdominal disease.
The researchers acknowledged that their study had various limitations. For example, it was possible that other possible pain-causing diseases could influence salivary alpha-amylase values.
“The results of this study could not be extrapolated to situations of pain produced by other diseases such as laminitis or synovitis, and specific studies to evaluate the dynamics of both salivary biomarkers in pain conditions should be performed.”
They continued: “Although … the number of horses used in our study was enough to evaluate differences between clinical and control horses, further studies involving a larger number of horses with acute abdominal disease would be recommended in order to confirm the relationship between salivary alpha-amylase and pain.
“It is important to point out that pain evaluation does not replace clinical decision making (which is made based on physical examination, blood results, ultrasound, and other diagnostic tests), but its objective evaluation by biomarkers could help to better evaluate the patient at admission and also to improve the follow-up during the treatment.
“In addition, it would be of interest to analyze a population of horses admitted to a hospital for non-painful, elective procedures to investigate the effect of other variables that cause stress for horses, such as transport and arrival to an unfamiliar facility, in the salivary biomarkers assessing in this study.
“Eventually, these studies could even lead to include salivary alpha-amylase in future pain scales as a pain-induced stress biomarker.”
The full study team comprised María Dolores Contreras-Aguilar, Damián Escribano, Fernando Tecles and Jose Joaquín Cerón, all from the University of Murcia in Spain; and María Martín-Cuervo, from the University of Extremadura.
Salivary alpha-amylase activity and cortisol in horses with acute abdominal disease: a pilot study
María Dolores Contreras-Aguilar, Damián Escribano, María Martín-Cuervo, Fernando Tecles and Jose Joaquín Cerón
BMC Veterinary Research 2018 14:156 https://doi.org/10.1186/s12917-018-1482-4