Abstract
Gastrointestinal nematodes (GIN) are a serious concern for sheep producers worldwide. However, there is a paucity of evidence describing the epidemiology of GIN on modern UK sheep farms. The aim of this paper was to understand whether expected seasonal variations of infection are still found in ewes and lambs under varying management strategies in temperate climates. Faecal egg counts (FEC) were conducted on freshly voided samples collected from groups of ewes and lambs every third week for twelve months on three farms in southeast Scotland. The patterns of egg output have been described here in relation to management practices undertaken on the farms. Despite changes in farming practice and climatic conditions, the findings complement historical studies detailing the epidemiology of GIN. Findings include a periparturient rise in ewe FEC on two of the farms, while lambing time treatment appeared to suppress this on the third farm. On the same two farms lamb FEC increased during the summer, reaching a peak in the autumn. The work also highlights how the ad hoc use of anthelmintics does little to impact these patterns.
Highlights
Current planned management of ovine gastrointestinal nematodes (GIN) in temperate climates is largely based on epidemiological studies that are becoming increasingly dated (Morgan et al, 1951; Parnell, 1954; Brunsdon, 1970; Coop et al, 1990)
There were distinct overall patterns in ewe Faecal egg counts (FEC) through the study period, with a periparturient rise (PPR) observed on all three farms between April and July 2016
The PPR appeared to be shortened on Farm 1 in association with the lambing-time moxidectin treatment (Cydectin Oral Drench; Zoetis UK limited)
Summary
Current planned management of ovine gastrointestinal nematodes (GIN) in temperate climates is largely based on epidemiological studies that are becoming increasingly dated (Morgan et al, 1951; Parnell, 1954; Brunsdon, 1970; Coop et al, 1990). These refer to farming systems prior to the introduction of the most recent broad-spectrum anthelmintic drug classes, the recognition of climate change and the widespread development of anthelminthic resistance (Sargison et al, 2007; Mitchell et al, 2010; Glover et al, 2017; Hamer et al, 2018). Pasture contamination is thought to decline in autumn and winter in temperate climates, when lamb immunity increases, stocking densities decrease and larval development reduces due to decreased ambient temperatures (Armour, 1986; Smith and Grenfell, 1994)
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