Evaluation of Stress During Hospital Visits in Retired Racing Greyhounds With and Without Diarrhea
Anecdotal evidence and our clinical experience suggest that acute large bowel diarrhea is common in a subset of healthy Greyhounds presented to veterinary hospitals. In this study, we examined the influence of activation of the stress response system on the development of diarrhea by evaluating both the hypothalamic-pituitary-adrenocortical (HPA) axis (i.e., increased cortisol concentrations in plasma and saliva) and the sympatho-adrenomedullary (SAM) axis (i.e., increased epinephrine and norepinephrine concentrations in plasma). By evaluating salivary cortisol concentrations (SAL CORT), we compared the stress response in the hospital to the baseline level of "stress" detected in the home environment in order to better understand the cause of the acute diarrhea in Greyhounds. We hypothesized that most Greyhounds would have a higher SAL CORT in the hospital than at home, and that Greyhounds with high salivary and plasma cortisol concentrations would be more likely to develop diarrhea at the hospital.
Two groups of Greyhounds were evaluated, including 36 healthy blood donor Greyhounds (group 1) and 32 recently retired racing Greyhounds being housed at the hospital for one week to be spayed and neutered (group 2). In group 1, saliva samples were taken at home by the owners prior to arrival at the hospital and at least 48 hours after their hospital visit; in group 2, saliva samples were taken at arrival and at least 2 days after surgery. For both groups, stool, saliva, and blood samples were obtained in the hospital. Stool samples were scored to determine if the dog had diarrhea or formed feces; salivary cortisol and plasma epinephrine, norepinephrine, and cortisol concentrations were also determined.
There was a strong correlation (p<0.001) between salivary and plasma cortisol concentrations. For group 1, the SAL CORT in the samples obtained by owners in the home environment were significantly lower (p<0.001 for "pre-visitation" and p<0.01 for "post-visitation") than those obtained during the hospital visit. For group 2, there was no significant difference between initial cortisol samples and those obtained post-surgery. During their first day in the hospital, 8 (11.8% of total) Greyhounds developed diarrhea, and 13 (19.1% of total) Greyhounds developed diarrhea within that week. Greyhounds with diarrhea had significantly higher plasma cortisol concentrations (p<0.001) than those without diarrhea; there were no significant differences in the concentrations of epinephrine or norepinephrine between Greyhounds with and without diarrhea.
As suggested by the high plasma cortisol concentrations in the affected dogs, the HPA axis is likely involved in the development of acute diarrhea in Greyhounds arriving at the hospital. Since SAL CORT corresponded well with plasma cortisol concentrations, this allows for a non-invasive measurement of stress that can be utilized in the home environment, as a baseline for subsequent samples, and promotes increased accuracy by avoiding the "white coat effect". The Greyhounds in group 1 appeared to return to a normal level of "stress" within 2 days of returning home, and the dogs in group 2 retained high cortisol concentrations (corresponding well with the prolonged hospital stay and their recent surgeries).