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The objectives of this study were to determine the prevalence of S. equi in a horse population in Colombia, to determine the risk factors associated with its detection in the guttural pouches and to report the antimicrobial susceptibility of the isolates. Fifteen farms and 137 horses >6 months of age were enrolled. Sampling was randomly, stratified and proportional to the population size of each farm. The guttural pouch (GP) was swabbed via endoscopic guidance and culture was performed. DNA extraction and conventional PCR were performed in colonies compatibles with S. equi, the PCR products were sequenced and subjected to BLAST analysis. Antimicrobial drug sensitivity was assessed using an antimicrobial disc diffusion assay including penicillin, ceftiofur, trimethoprim-sulfamethoxasole (TMS), enrofloxacin and oxytetracycline. A mixed logistic regression model was constructed to evaluate risk factors associated with the presence of S. equi. The S. equi culture prevalence in the GP was 15%; 13.5 % for S. equi subsp. equi and 1.5% for S. equi subsp. zooepidemicus. History of travel was associated with the presence of S. equi, whereas every 1-year increase in age decreased the risk for S. equi detection in the GP. All isolates were susceptible to TMS, ceftiofur and penicillin, but resistant to enrofloxacin and oxytetracycline. S. equi is present in horses in Colombia, with a high prevalence and appear to be endemic in the tested population. Younger horses and horses with recent history of travelling had higher odds of testing positive for S. equi in swabs of the GP., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest., (Copyright © 2022. Published by Elsevier Inc.)

This study aimed at describing selected hematological, biochemical, and acid-base variables of adult horses living at sea level and comparing them to those living at 5 different altitudes. One hundred and thirty-eight healthy Paso Fino horses > 2 years old were enrolled. Altitudes included the following: altitude A (0 to 50 m above sea level, masl; n = 23), B (1000 to 1050 masl; n = 25), C (1450 masl; n = 30), D (1950 to 2050 masl; n = 30), and E (2950 to 3100 masl; n = 30). A portable blood gas analyzer was used to determine selected biochemical and acid-base variables. Hematocrit (Htc) was measured by blood centrifugation and total plasma protein as total solids using a refractometer. A one-way ANOVA with Tukey's HSD post hoc test or a Wilcoxon signed-rank test, depending of the normality of the data, was conducted to compare groups. Horses at sea level had lower Htc (25% ± 2) and Hb (8 ± 0.8 mg/dL) concentration than those horses living ≥ 1000 masl (P < 0.05, for all comparisons). No differences in Htc and Hb were identified in horses living between 1000 and 3000 masl (P > 0.05, for all comparisons). The venous P v CO 2 was significantly lower in horses living at altitudes ≥ 1000 masl than those living at 0 masl (42 ± 4.8 mmHg) (P = 0.001, for all comparisons). No differences in P v CO 2 were identified in horses living between 1000 and 3000 masl. This study showed that the Htc, Hb, and P v CO 2 of horses living at sea level were different compared to those in healthy horses living at altitudes ≥ 1000 masl. However, differences in TPP and electrolyte concentrations were not identified.