In vivo and in vitro anthelmintic activity of quebracho-chestnut tannin extract against Haemonchus contortus in lambs.

Haemonchus contortus is considered the most pathogenic gastrointestinal nematode of sheep and, due to the increasing resistance to synthetic anthelmintics, it poses a serious challenge to small ruminant production systems. The aim of this work was to evaluate the in vivo and in vitro anthelmintic activity of quebracho-chestnut tannin extract against Haemonchus contortus in lambs. The in vitro assays (egg hatching inhibition and larval migration inhibition) were performed to determine the effective concentrations required to inhibit 50% of egg hatching and larval migration (EC50), which were 3.8 and 1.4 mg/mL, respectively. For the in vivo trial, 18 lambs used were divided into three groups: Group 1 (control), Group 2 (a tannin dose equivalent to 0.3% of dry matter intake), and Group 3 (a tannin dose equivalent to 3% of dry matter intake). No significant differences (p > 0.05) were observed among treatments in faecal egg counts, larval counts from coprocultures, or adult H. contortus recovery. The tannin extract was effective in inhibiting egg hatching and larval migration in vitro at low concentrations. However, when administered in vivo at 0.3% and 3% of dry matter intake, it failed to show any effect on faecal egg counts, larval counts in coproculture, or adult worm burden. Adult worms, eggs, and infective larvae were further examined using scanning electron microscopy. The observations revealed significant cuticular alterations in adult worms, which could potentially interfere with normal feeding and reproductive processes. Additionally, eggs and infective larvae exhibited shell rupture and cuticle damage.