Implementation of Targeted Selective Treatment (TST) in a Commercial Smallholder Sheep Flock: Reduction in Anthelmintic Expenditure

The adoption of targeted selective treatment (TST) is an alternative for the sustainable management of gastrointestinal nematodes in sheep. TST mitigates the development of anthelmintic resistance by reducing the number of animals drenched while preserving the parasite refugia population. This study analysed the reduction of anthelmintic (AH) usage and assessed the AH cost reduction derived from a TST program compared to the previous whole‐flock treatment regimen on a commercial smallholder sheep farm. Data acquisition spanned a 4.75‐year period on a smallholder meat sheep farm in Colombo, Paraná, Brazil, maintaining an average adult flock size of 45 sheep, including 43 ewes and 2 rams. Prior to TST implementation, all animals were treated monthly with AH. A fecal egg count reduction test (FECRT) was conducted prior to implementation, and levamisole was the AH with the best efficacy, with 90% (95% CI: 79%–94%) of FEC reduction. The TST protocol was based on the FAMACHA system, body condition score, and the presence of submandibular oedema as criteria for administering AH treatments. Throughout the studied period, TST evaluations were conducted monthly and upon the farmer's request. The number of sheep assessed and treated based on the TST criteria were tabulated and designated as TST group. To evaluate the reduction in AH expenditure after the implementation of the TST, a counterfactual simulated whole‐flock treatment (WFT) group was constructed, representing a scenario where all sheep continued to receive monthly AH treatment according to the previously established regimen. For cost calculation, the average live weight was estimated at 60 kg. Cost estimation was performed using the formula: number of sheep assessed per month × AH dosage × AH cost. Over the study period, a total of 2180 individual evaluations were conducted. The proportion of sheep treated varied seasonally: 12.0% in summer, 21.0% in autumn, 34.0% in winter, and 25.0% in spring. Overall, 25.0% of assessed animals received AH treatment. The cumulative cost of AH treatments for the TST group over 4.75‐year period was US$67.68. In contrast, the projected cost for the simulated WFT group using levamisole was US$271.61, although costs for other anthelmintic classes ranged up to US$2744.66. The use of TST reduced the number of AH treatments compared to simulated WFT regimen, thereby lowering costs associated with parasite control.