Anthelmintic stewardship: An essential step towards sustainable dairy farming.

Helminth infections in grazing dairy cattle can lead to asymptomatic infections, subclinical- or clinical disease. Whether the course of infection leads to disease depends on various factors, leading to a broad variety of prevalence rates and severity of disease between farms, between groups of cattle in a farm and between individual animals. Production losses related to helminth infections, the difficulty in diagnosing helminth disease and the wide availability and high efficacy of anthelmintics have led to overreliance on these products. Combined with management and other factors, this results in the development of anthelmintic resistance and an environmental hazard of drug residues. To slow down the development of anthelmintic resistance and to reduce the consequences of anthelmintic use on the environment, anthelmintic stewardship (AHS) is urgently needed. We define AHS as a systematic approach to optimize the management of helminth infections with the goal to minimize their negative consequences through minimizing the usage of anthelmintics, reducing the development of anthelmintic resistance and reducing environmental contamination. Implementation of AHS requires an approach that considers the complexity of helminth infections weighing different interests, while transferring them to practical applications. An integrated approach implementing AHS on dairy farms is proposed, consisting of four steps: risk assessment, prevention, diagnostics, and treatment. For each of these steps, implementation possibilities and gaps are reviewed. Although there are knowledge and implementation gaps in each of the steps, enough tools are currently available to implement AHS based on the proposed four step approach on dairy farms.