Antinematicidal Activity of Nicotiana tabacum L. Leaf Extracts to Control Benzimidazole- Resistant Haemonchus contortus in Sheep

This study was carried out to assess the efficacy of nicotiana (n.) tabacum leaves to control benzimidazole-resistant haemonchus (h.) contortus in sheep. fecal egg count reduction test (fecrt) and egg hatch assay (eha) revealed catastrophic levels of resistance in h. contortus of sheep against oxfendazole, a member of benzimidazole group of antinematicidals. antinematicidal efficacy of n. tabacum leaves was evaluated employing eha, adult motility test (amt) and fecrt. there was a dose and time dependent antinematicidal activity of crude aqueous methanol extract (came) of n. tabacum leaves with estimated lc50 values of 0.566 and 1.91 mg ml^-1 in eha and amt, respectively. there was, however, no significantdifference (p>0.05) in fecal egg count reduction (87.5 vs 88.6%) in sheep at low (2 g kg^-1 bw) and high (4 g kg^-1 bw) doses of came of n. tabacum leaves. administration of n. tabacum leaves at low dose (2 g kg^-1 bw) did not exhibit untoward effects in animals; therefore, may be used in sheep harboring antinematicidal- resistant populations of h. contortus.