Larval challenge does not cause production loss in sheep given continuous anthelmintic treatment: Creating a worm-free sheep with a controlled release capsule

Measuring loss of production due to infection with gastrointestinal nematode parasites (worms) in the field poses significant difficulties in the provision of worm free controls. Past approaches have relied on frequent anthelmintic administration or the use of controlled release capsules (CRCs) to suppress worm burdens. These approaches do not prevent intake of L3 which may trigger a host immune response and contribute to the pathophysiology of worm infection. This study aimed to quantify the cost of larval challenge in sheep administered a CRC and thus determine the suitability of CRC treated sheep to be a proxy for worm-free sheep in grazing experiments.