Does a repellent effect contribute to reduced levels of insect activity in dung from cattle treated with ivermectin?

Abstract

A two-year pitfall trapping study was performed to test the preference of coprophilous beetles (Hydrophilidae, Scarabaeidae, Staphylinidae) for dung from untreated cattle versus dung from cattle treated topically one or four weeks previously with a recommended dose of ivermectin in a pour-on formulation. In 1994, significantly more Aphodius fimetarius (Linnaeus) and A. distinctus (O.F. Miiller) at each of two sites were collected with dung from treated cattle. No differences were detected for other taxa. In 1995, significantly fewer individuals of ten taxa, including A. fimetarius and A. distinctus, were collected with dung from treated cattle. No differences were detected for other taxa. A change in cattle diet may have altered levels of faecal residues, thereby changing beetle preferences between years. Comparisons between periods of spring and autumn activity identified a change in seasonal preferences for at least some species. Similar numbers of Onthophagus nuchicornis Linnaeus and of A. fimetarius were collected in spring with dung from treated or untreated cattle, but significantly more individuals of both taxa were collected in autumn with dung from untreated cattle. In contrast, the preference of Aphodius prodromus Brahm for dung from treated cattle was unchanged between spring and autumn. These results show that ivermectin therapy does influence the colonization of dung from treated cattle. However, the nature of this influence is confounded by extraneous factors. Until such time that these factors can be accounted for, general predictions regarding the effect of ivermectin therapy on the colonization of dung by coprophilous insects are premature.

Nontarget Effects of Ivermectin on Coprophagous Insects in Japan

“…It has been reported that some dung-beetles were more attracted to dung from treated cattle than dung from control cattle (Wardhaugh and Mahon 1991, Holter et al 1993, Floate 1998b. Holter et al (1993) showed that Liatongus sp.…”

Influence of dung volatiles on the process of resource selection by coprophagous beetles

“…The effects of fecal residues of antiparasitic drugs on the process of colonization by dungfeeding insects remain unclear (Floate et al 2005). Cattle dung from treated animals has been shown to be either more attractive (Wardhaugh & Mahon, 1991;Holter et al 1993;Lumaret et al 1994) or much less attractive than those from untreated animals (Floate 1998) to dung beetles in the field. A comparison of the chemical composition of dung odours revealed notable differences between the content of volatile compounds in dung of sheep, cattle, horse and deer (Dormont, unpublished).…”

“…Dung was taken from untreated animals because antiparasitic drugs administered to herbivorous mammals possibly influence the attractiveness of their dung to insects (Wardhaugh & Mahon 1991;Floate 1998). The dung was collected fresh from several pats (immediately after defecation, before arrival of any coprophagous animals) and was thoroughly mixed together to homogenise it and to avoid possible differences in physical and chemical composition among individual pats.…”

How to test nontarget effects of veterinary pharmaceutical residues in livestock dung in the field

“…Use of VMPs can affect colonization such that more or fewer insects may lay eggs in dung of treated livestock (Floate 1998a(Floate , 2007Holter et al 1993;Wardhaugh and Mahon 1991). The insecticidal activity of residues in such dung may be somewhat underestimated if it initially contains a larger starting population of insects relative to control dung and vice versa.…”