Effect of repeated wattle tannin drenches on worm burdens, faecal egg counts and egg hatchability during naturally acquired nematode infections in sheep and goats

In vivo and in vitro experiments were carried out to investigate the effect of repeated wattle tannin (WT) drenches on faecal egg counts (FEC), worm burdens and egg hatchability during a naturally acquired worm infection in sheep and goats. For the in vivo experiment, nematode-infected sheep and goats were orally drenched with WT at a dose of 1.3g and 1.6gWT/kg bodyweight per day for three consecutive days respectively while a control group received a placebo. FEC and other worm infection parameters were monitored regularly. Once a surge in faecal egg profiles was evident the drenching exercise was repeated as explained above. The trials were terminated by humane slaughter of all the animals and estimation of worm burdens recovered from their guts. WT drench did not, significantly, reduce FEC or total worm burdens in goats. However, there was a slight reduction in FEC and a significant reduction in Haemonchus contortus worm burdens in sheep. WT drenches were also associated with increased faecal water and mucus contents. The in vitro work involved the use of an egg hatch assay using faeces from WT-drenched and un-drenched goats. A dose-response experiment whereby goat faeces were spiked with different levels of WT and then cultured for larval count comparisons was also carried out. The presence of WT in culture media significantly (P<0.05) reduced egg hatchability. There was a significant negative regression coefficient (R2=0.84; P<0.01) between concentration of WT in culture media and percent hatchability of nematode eggs. It is concluded that although the degree of anthelmintic activity of WT drench was limited, especially in goats, the drench was capable of reducing the hatchability of eggs passed out in faeces. © 2010 Elsevier B.V.