Ecology of the free-living stages of goat gastrointestinal nematodes during spring-summer contamination in Salta province, Argentina.

In small ruminants such as goats, gastrointestinal nematodes (GINs) are a major cause of disease, production loss and mortality. This study aimed to describe the dynamics of development and survival in both fecal matter and grass of the free-living stages of goat GINs during the rainy season in Salta Province, Argentina. Four experimental fecal contaminations were conducted on plots between October 2022 and April 2023, representing different seasonal conditions. Larval development time and rate, time of L3 larvae persistence in fecal matter and grass, and migration to pasture, as well as the relationships of these parameters with environmental variables were evaluated. Significant differences were observed in all parasitological parameters between experimental plots. Development time ranged from 8 to 50 days, with slower development under early spring conditions, and was negatively correlated with humidity and accumulated rainfall. The development rate varied between 3.9% and 12.3% and showed a positive association with maximum temperature. The time of L3 larvae persistence time in fecal matter differed markedly between periods, with the longest survival observed in April, as confirmed by Kaplan-Meier analysis. The migration of larvae to pasture occurred between 4 and 12 days after detection in feces and was strongly influenced by rainfall and fecal dry matter. The time of L3 larvae persistence in pasture ranged from 30 to 53 days, with higher survival during early periods. The genus Trichostrongylus exhibited greater ecological plasticity and persistence than Haemonchus and Teladorsagia. These findings highlight the strong influence of environmental conditions on GIN epidemiology and provide the first local evidence describing the refuge dynamics of GINs in goats in Argentina. This information may contribute to the design of more effective and sustainable parasite control strategies.