Table 2.

Effective concentrations of anthelmintics inhibiting 50% (EC₅₀) and 99% (EC₉₉) of larvae in gastrointestinal nematode (GIN) populations from herds classified as susceptible and resistant, presented as the median, interquartile range (IQR), and range in parenthesis

GIN population	No. of herds	EC50	EC99
Benzimidazoles – discriminating concentration (DC) = 0.08 μg/ml
susceptible	5	0.003, 0.003–0.007 (0.001–0.009)	0.011, 0.008–0.014 (0.001–0.042)
resistant	37	0.150, 0.050–0.301 (0.014–1.649)	2.990, 0.872–7.371 (0.135–974.682)
Macrocyclic lactones – DC = 21.6 ng/ml
susceptible	2	0.892 (0.135–1.649)	14.902 (13.398–16.400)
resistant	40	49.402, 24.533–77.576 (3.669–148.413)	1092.628, 396.322–3122.438 (47.127–257,437.7)
Levamisole – DC = 2.0 μg/ml
susceptible	37	0.202, 0.135–0.301 (0.025–0.549)	0.724, 0.480–1.148 (0.062–2.185a)
resistant	5	0.497, 0.449–0.741 (0.301–2.718)	6.446, 3.121–231.343 (2.824–269.110)

^a GIN populations from two herds (no. 5 and 23 in Table 1) were classified as susceptible despite ED₉₉ > 2 μg/ml because the corrected percentage larval development at the DC was ≤1%