Characterization of Gastrointestinal Parasites in Grazing Sheep in Mountain, Piedmont, and Savanna Conditions of Casanare, Colombia.

Gastrointestinal parasitosis represents a significant constraint on sheep productivity in Colombian tropical production systems; however, their regional epidemiological dynamics remain insufficiently characterized. Therefore, the objective of this study was to characterize the prevalence, associations, coinfestations, and health-related correlations of gastrointestinal parasites in grazing sheep from the Mountain, Piedmont, and Savanna ecoregions of the Department of Casanare, Colombia. A cross-sectional observational study was conducted, including quantitative and qualitative coprological examinations, assessments of environmental and production-related factors, and animal-level clinical indicators (FAMACHA score and body condition score). Data were analyzed using bivariate analyses (chi-square or Fisher's exact test) and nonparametric comparative tests (Mann-Whitney U or Kruskal-Wallis test), as appropriate. The overall prevalence was high (78.3%), with higher values in the Mountain ecoregion (90%) compared with the Piedmont (76.7%) and the Savanna (76.1%). A statistically significant association (p < 0.05) was identified between municipality, the water source, and parasitic prevalence. Parasitic burden differed significantly among ecoregions (p < 0.05). No correlation was observed between animal-level clinical indicators and parasite burden (ρ < 0.065). The distribution of parasite load was aggregated, with a predominance of mild infestations and a small subset of animals harboring burdens exceeding 5000 eggs per gram. Frequent coinfestations among nematodes, protozoa, and cestodes were identified, involving low-intensity associations. Despite the high prevalence, no clinically relevant health alterations were detected. Gastrointestinal parasitosis exhibited high prevalence, an aggregated distribution of parasite burden, and frequent low-intensity coinfestations, with variation among ecoregions and no association with clinical indicators. These findings suggest a dynamic process modulated by environmental and management-related factors, indicating host resilience and highlighting the need for targeted control strategies and longitudinal monitoring.