The cost of anthelmintic resistance

Resistance to the older anthelmintic groups is rising 4. In 2013 almost half the south west farms tested as part of the Healthy Livestock project had triple resistance. Interestingly, farmers who suspected they had resistance on farm were most likely have resistance to only one anthelmintic group (78%).

Source: Healthy Livestock, 2013

The first case of resistance to Zolvix (Group 4 -AD/ Orange) was reported in the UK last year3.

Cost of parasite control

Preparing a parasite control and grazing plan = £488

Annual costs based on 1000 ewe flock (72kg)

Quarantine treatments


Tests for resistance

Post-treatment, and pre- and post-treatment drench tests = £50.12 and £100.24 respectively

FECRT for three anthelmintic classes = £672.75

Larval development tests for Group 2-LV = £75.51

Effective administration

Additional work required to ensure effective treatment = £54.23

Targeted treatment

FEC without larval culture= £375.90
FEC with larval culture = £1157.40

Source: Learmount et al, 2018

Maintaining in refugia populations using SCOPS

Anthelmintic costs
SCOPS approach Whole farm Difference Ewes
Ewes £47.13 £224.10 -£176.97
Lambs £259.92 £300.87 -£40.95

Source: Learmount et al, 2018

Labour costs
SCOPS approach Whole farm Difference Ewes
Ewes £150.00 £640 -£490
Lambs £840 £1180 -£340

Source: Learmount et al, 2018

Production benefits

Lambs receiving effective treatment measured a 10.2% greater mean daily liveweight gain resulting in finishing 13 days earlier than those receiving ineffective treatment 2.

Cost of extra 13 days to finish

Source: Estimated costs from Learmount et al, 2018 based on the findings of Geurden et al, 2014.

Cost benefit

Source: Learmount et al, 2018

The greatest cost benefits were achieved when FEC was carried out without larval culture and when all replacements were bred on farm.
As the number of doses required declines over time without negatively impacting on production, returns could be expected to increase following an initial investment.


1Nieuwhof, G.J. and Bishop, S.C., 2005. Costs of the major endemic diseases of sheep in Great Britain and the potential benefits of reduction in disease impact. Animal Science, 81(1), pp.23-29.
2Geurden, T., Hoste, H., Jacquiet, P., Traversa, D., Sotiraki, S., di Regalbono, A.F., Tzanidakis, N., Kostopoulou, D., Gaillac, C., Privat, S. and Giangaspero, A., 2014. Anthelmintic resistance and multidrug resistance in sheep gastro-intestinal nematodes in France, Greece and Italy. Veterinary parasitology, 201(1-2), pp.59-66.
3Hamer, K., Bartley, D., Jennings, A., Morrison, A. and Sargison, N., 2018. Lack of efficacy of monepantel against trichostrongyle nematodes in a UK sheep flock. Veterinary parasitology257, pp.48-53.
4Learmount, J., Glover, M.J. and Taylor, M.A., 2018. Resistance delaying strategies on UK sheep farms: A cost benefit analysis. Veterinary parasitology, 254, pp.64-71.Moredun