Ten years of gastrointestinal parasite monitoring in Zerasca Sheep

The monitoring of gastrointestinal nematodes can aid in administering anthelmintic treatments limited to the effective cases. This approach can serve as a valuable tool for safeguarding animal welfare, the environment, and the quality of animals’ derived products. Finally, yet importantly, it could be useful for containing the occurrence of drug resistance. This study aimed to describe ten years of monitoring gastrointestinal nematode (GIN) burden in a farm of Zerasca sheep located in the North of Tuscany (Italy) which has not been treated with anthelmintics since 2012. Additionally, the study aimed to evaluate the influence of the date of sampling, the year, and the season on GIN and the correlation between the body condition score (BCS) and eggs per gram (EPG). Faecal samples were regularly collected to estimate the faecal egg count of GIN, expressed as eggs per gram (EPG), using a modified McMaster technique. BCS was checked using a scale ranging from one to five. Results of Fecal Egg Count were grouped into four levels of infection (0=0 EPG; 1=1-300 EPG; 2=301-600 EPG; 3=more than 600 EPG). The study reveals significant fluctuations in gastrointestinal nematode burdens in sheep over ten years. The overall mean of EPG was 286.5 ± 620.28, with notable variations observed across sampling dates (P≤0.001). Although EPG levels varied over the years (P=0.0002), no significant differences were found across seasons (P=0.9040). The sheep population exhibited infestation predominantly falling within lower levels (0 and 1), but attention to health is warranted for the 14.7% exceeding 600 EPG. BCS and EPG showed a significant negative correlation (r = -0.2295; p=0.0051), indicating that BCS could serve as an indirect indicator of infestation levels. The study underscores the need to reevaluate GIN management strategies considering climate change and anthelmintic resistance. Targeted treatments for heavily infested animals, alongside maintaining anthelmintic susceptibility through refugia, are suggested as alternative approaches to widespread chemical treatments, which may contribute to resistance development and environmental contamination.