Age-dependent spatial patterns of gastrointestinal parasites in goats across an extensive mountainous system in...

Understanding how host age interacts with environmental heterogeneity to shape the spatial distribution of gastrointestinal parasites is essential for improving control strategies in extensive grazing systems. This study evaluates age-dependent and spatial patterns of gastrointestinal parasites in 635 goats from an extensive mountainous system, in Valle Fértil, San Juan Province, western Argentina. Fecal samples were analyzed using the McMaster and sedimentation techniques, and spatial structure was assessed using Global and Local Moran's I indices. Eimeria spp. was the most prevalent parasite (>91.3%) and exhibited strong spatial clustering, suggesting transmission driven by localized environmental conditions, potentially associated with seasonal corral confinement. Strongyle-type nematodes showed distinct age-dependent spatial patterns: juveniles (<12 months) displayed strong spatial autocorrelation indicative of structured environmental risk, whereas adults (>36 months) showed a near-random distribution, consistent with age-related differences in susceptibility and exposure patterns. Fasciola hepatica was detected for the first time in goats from this region. Despite the absence of anthelmintic interventions, parasite excretion levels were relatively low, consistent with extensive management and low stocking density. These findings suggest that age-related differences may influence spatial infection patterns and support the use of young animals as bioindicators of environmental infection pressure in heterogeneous grazing systems.