Surveillance and farmer perception of gastrointestinal nematode infections in sheep farms: A 10-year retrospective study

Gastrointestinal nematodes (GINs) are ubiquitous in grazing ruminant production systems and are responsible for significant production losses, especially on sheep farms. Control programmes of these parasites in ruminants are based on using anthelmintic drugs. The emergence of anthelmintic resistance, together with global warming, is responsible for the changing epidemiology of these helminths in many geographical areas. Long-time helminth surveillance of GIN infections is paramount to defining control strategies. This study aimed to investigate GIN infections in sheep farms by integrating parasitological data with data collected by questionnaire. The analysis focused on the variability of GIN burden (eggs per gram of faeces - EPG), in order to evaluate the role of surveillance in supporting sustainable helminth control strategies. A structured questionnaire was developed and validated to collect detailed information on farms. The study also explored farmers’ perceptions of helminth infections and their perceived impact on milk and meat production. Parasitological data were obtained from a ten-year helminth surveillance (2013–2023) of the Regional Center for Monitoring Parasitic Infections (CREMOPAR, Campania region, Italy) on 138 sheep farms sampled in southern Italy. A retrospective observational study according to the STROBE statement was performed. The variables and covariates were analysed using a machine learning model for advanced data analysis, in particular, classification tree and random forest. The results of this retrospective study spanning ten years indicated that as the averages and medians of the number of Faecal Egg Count Analysis (FEC Analysis) increased, a decline in the average helminth burden was observed for each FEC Analysis. The validated questionnaire showed good internal consistency and was effective in capturing data on farm management and farmer perceptions. Machine learning models identified treatment frequency, administration method, and farmer awareness of anthelmintic resistance as key predictors of improved production outcomes. Differences in productivity were also observed between dairy and meat systems, with breed and pasture size playing significant roles. Notably, younger farmers demonstrated more effective management strategies. Environmental factors, such as proximity to water sources, influenced meat production levels. The study highlights the importance of regular parasitological monitoring and evidence-based management in improving helminth control and farm productivity. The findings support the integration of diagnostic tools, farmer education, and predictive models to optimize treatment strategies and promote sustainable parasite control in sheep farming systems. Therefore, monitoring is the basis for setting up a correct control strategy for GINs.