The effects of dung beetle activity on the numbers of parasitic gastrointestinal helminth larvae recovered from pasture samples

Abstract

Studies have been made of the effect of the dung beetle, Onthophagus gazella, on the release of strongyle larvae from cattle faeces onto pasture. A series of faecal pats containing parasitic nematode eggs was placed on pasture, and beetles were added to some pats to give three levels of beetle activity, viz. 100 g, 200-250 g, and 500 g of faeces per pair of beetles. These pats were duplicated on irrigated and non-irrigated pasture. In both cases the numbers of strongyle larvae migrating from pats attacked by dung beetles were significantly less than those migrating from control pats containing no dung beetles. Compared with larval recoveries from control pats, the percentage reduction in numbers of larvae migrating from pats on irrigated pasture was 50% for pats of 100 g faeces per pair of beetles, 48 % for pats of 200-250 g faeces per pair, and 84% for pats of 500 g of faeces per pair. The respective figures for pats on nonirrigated pasture were 76, 86, and 93 % reduction in larval numbers. The results indicated that strongyle larvae migrated from faecal material buried by dung beetles, provided soil moisture was adequate. More larvae were recovered from the pasture surrounding irrigated faecal pats attacked by beetles than from the non-irrigated pats. During warm dry weather, surface faecal debris remaining after beetlc attack appeared to be helminthologically sterile.