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In the UK, recent mean temperatures have consistently increased by between 18C and 48C compared to the 30-year monthly averages. Furthermore, all available predictive models for the UK indicate that the climate is likely to change further and feature more extreme weather events and a trend towards wetter, milder winters and hotter, drier summers. These changes will alter the prevalence of endemic diseases spatially and/or temporally and impact on animal health and welfare. Most notable among these endemic parasites are the helminths, which have been shown to be very strongly influenced by both the shortterm weather and climate through effects on their free-living larval stages on pasture. In this review, we examine recent trends in prevalence and epidemiology of key helminth species and consider whether these could be climate-related. We identify likely effects of temperature and rainfall on the free-living stages and some key parasite traits likely to determine parasite abundance under changed climatic conditions. We find clear evidence that climate change, especially elevated temperature, has already changed the overall abundance, seasonality and spatial spread of endemic helminths in the UK. We explore some confounders and alternative explanations for the observed patterns. Finally, we explore the implications of these findings for policy makers and the livestock industry and make some recommendations for future research priorities.

Due to the development of anthelmintic resistance, there have been calls for more sustainable nematode control practices. Two important concepts were introduced to study and promote the sustainable use of anthelmintics: targeted treatments (TT), where the whole flock/herd is treated based on knowledge of the risk, or parameters that quantify the severity of infection; and targeted selective treatments (TST), where only individual animals within the grazing group are treated. The aim of the TT and TST approaches is to effectively control nematode-induced production impacts while preserving anthelmintic efficacy by maintaining a pool of untreated parasites in refugia. Here, we provide an overview of recent studies that assess the use of TT/TST against gastrointestinal nematodes in ruminants and investigate the economic consequences, feasibility and knowledge gaps associated with TST. We conclude that TT/TST approaches are ready to be used and provide practical benefits today. However, a major shift in mentality will be required to make these approaches common practice in parasite control.

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Infections with parasitic helminths (nematodes and trematodes) represent a significant economic and welfare burden to the global ruminant livestock industry. The increasing prevalence of anthelmintic resistance means that current control programmes are costly and unsustainable in the long term. Recent changes in the epidemiology, seasonality and geographic distribution of helminth infections have been attributed to climate change. However, other changes in environment (e.g., land use) and in livestock farming, such as intensification and altered management practices, will also have an impact on helminth infections. Sustainable control of helminth infections in a changing world requires detailed knowledge of these interactions. In particular, there is a need to devise new, sustainable strategies for the effective control of ruminant helminthoses in the face of global change. In this paper, we consider the impact of helminth infections in grazing ruminants, taking a European perspective, and identify scientific and applied priorities to mitigate these impacts. These include the development and deployment of efficient, high-throughput diagnostic tests to support targeted intervention, modelling of geographic and seasonal trends in infection, more thorough economic data and analysis of the impact of helminth infections and greater translation and involvement of end-users in devising and disseminating best practices. Complex changes in helminth epidemiology will require innovative solutions. By developing and using new technologies and models, the use of anthelmintics can be optimised to limit the development and spread of drug resistance and to reduce the overall economic impact of helminth infections. This will be essential to the continued productivity and profitability of livestock farming in Europe and its contribution to regional and global food security