Salivary Cortisol, Equine Characteristics, and Management Factors Associated With Strongyle-Type Egg Shedding of Ohio Horses.

Identification of factors associated with parasite infestation in horses could reduce frequency of anthelmintic administration and slow development of anthelmintic resistance. The study aim was to evaluate management factors, equine characteristics, and equine salivary cortisol concentrations for association with strongyle-type egg shedding levels. As immunocompromised horses appear to be more susceptible to parasite infestation, it was hypothesized that salivary cortisol concentration could be associated with parasite egg shedding. Saliva and fecal samples were collected from 200 horses across the state of Ohio. Equine management questionnaires were administered to barn managers. Fecal egg counts were performed with a modified Stoll method, and saliva samples were analyzed for salivary cortisol with an enzyme-linked immunosorbent assay (ELISA). A total of 24 variables were tested for association with fecal egg count results (dichotomized with 50 eggs per gram as a cutoff) using chi-square test of independence, Fisher's exact test, independent t-test, or Mann Whitney U test. The sample of horses was partitioned into tertiles based on salivary cortisol concentrations (i.e., low <0.052 µg/dL, medium 0.052-0.0712 µg/dL, and high >0.0712 µg/dL). Variables with P < .30 were analyzed for association with fecal egg count with multiple logistic regression. The final logistic regression model (P< .05) included horse age, horse salivary cortisol concentration, and pasture mowing frequency. Older horses had higher adjusted odds of having <50 EPG. Pasture mowing frequency of at least once per week increased the adjusted odds of <50 EPG. Horses with cortisol concentrations in the highest tertile had increased adjusted odds of having <50 EPG.