Dung beetle activity and the development of trichostrongylid eggs into infective larvae in cattle faeces.

In the perspective to reduce the use of antiparasitic drugs, any interaction between the processes that control the development of parasite eggs into infective larval stages (L3) in dung and the activities of different dung-breeding organisms becomes of interest. The objective of the present study was to determine whether dung beetle activity affected the development of parasite larvae in cattle dung. Faeces containing eggs of parasites (predominately Cooperia spp.) were pooled according to high (250–600epg) or low (approx. 100epg) egg counts. Experimental dung pats were formed for each category of faeces and to half of these pats, dung beetles (20 Aphodius rufipes, 20 A. scybalarius syn. rufus) were added and kept for 12 days at 21°C (±1°C) and 90% RH (±5% RH). Beetles were then removed and the pats were divided in two where half the pat was incubated for an additional 12 days at 21°C (±1°C) and 90% RH (±5% RH) and the other half was immediately analysed. A greater number of L3 were recovered from the dung subjected to beetle activity compared with control dung (P<0.001). However, following an additional 12 days incubation of the dung, similar numbers of L3 were recovered from beetle-affected dung with high egg counts, whereas there were significantly greater numbers of L3 derived from the control dung (P<0.001). There was no significant difference in L3 recovery in the two categories of pats (i.e. high and low nematode egg counts). The results indicate that activity by Aphodius spp. in fresh dung can optimise conditions for nematode development to the infective larval stage if favourable environmental conditions prevail. Such synergistic effect may be due to the fact that dung beetles used in this study are dung dwellers, i.e. no substantial amount of the dung is removed or burrowed as these beetles feed, lay their eggs and the larval development takes place in brood chambers inside the dung.