Larvicidal Activity of Merck MK-933, an Avermectin, Against the Horn Fly, Stable Fly, Face Fly, and House Fly12

The numbers of insects colonizing the dung of cattle injected with the anthelmintics ivermectin or moxidectin were compared with the colonization of the dung from control animals given no treatment, in a blind field trial. Dung was collected 2, 7, 14, and 21 days after dosing and set out in a randomized grid of standard 2 kg pats. Pats were retrieved from each of the three groups group after 7, 14, 21 and 42 days in the field for analysis of insect fauna. There were no significant differences in the number of adult Aphodius spp. (Coleoptera: Scarabaeidae) found in the dung from the three treatment groups with either time of exposure in the field or time after treatment, showing that adult beetles were attracted to all pats equally. However, dung from animals treated with ivermectin prevented the development of larval Aphodius spp. for at least 7 days after treatment. In contrast, the dung from animals treated with moxidectin supported the development of Aphodius spp. at all stages after dosing, as did dung from control animals. There were no significant differences in the number of cyclorrhaphous Diptera larvae in dung from control or moxidectin-treated animals. In contrast, such larvae were largely absent from the dung collected from ivermectin-treated cattle for up to 14 days after dosing. The results show that moxidectin is less toxic to dung-inhabiting insects than ivermectin following standard injection treatment. The results are discussed in relation to the effects of anthelmintics on non-target pastureland insects.

Section: Discussionsupporting

confidence: 92%

Effects of ivermectin and moxidectin on the insects of cattle dung

Strong

Wall

1994

“…This fly will not develop in the dung of cattle injected up to 35 days previously (Schmidt, 1983), and thus it is reasonable to predict a level of biologically active metabolites equivalent to ivermectin at 0.006 ppm at 35 days after injection. Similarly, an oral dose of 1 ng per kg cow per day, which kills all H. irritans in the dung (Miller et al, 1981), indicates a pat concentration of active metabolites equivalent to ivermectin at 0.006 ppm. Of course, considerably higher levels are anticipated daily in the pats of cattle treated with a bolus releasing some 40 (ig per kg cow.…”

Section: Levels Of Ivermectin In the Faecesmentioning

confidence: 99%

Avermectins: a review of their impact on insects of cattle dung

Strong

1992

117

Avermectins administered to cattle for control of parasitic infections by injection or slow-release bolus are excreted in the faeces and have a variety of harmful effects upon Diptera and Coleoptera that develop in cow-pats: these effects are reviewed. Diptera Cyclorrhapha are severely affected, the extent of the response depending on the drug concentration in the dung. At high levels, larvae are killed or paralysed while at lower levels their metamorphosis is inhibited. At very low levels, adult emergence is reduced and a significant number of imagines show morphological abnormalities. These responses are induced by concentrations of avermectins well below levels occurring in faeces after routine treatment. Diptera Nematocera are less sensitive than Cyclorrhapha but larval and pupal development are affected at higher dose levels. Larval dung beetles and some immature adults cannot survive in the pats of recently dosed livestock. Mature adult beetles are more resistant, but contact with treated dung leads to impaired reproduction. Dung eliminated up to 5 weeks after cattle have been treated with a single injection or up to 14 days after topical dosing shows harmful activity against dung insects, and ivermectin-containing pats retain much of their toxicity after several weeks exposure on pastureland. The impact on dung insects is more pronounced and of longer duration when ivermectin is delivered daily at 40 (ig per kg cow by sustained-release bolus. Following topical or injection treatments, the rate of cow-pat degradation (measured by actual loss of biomass) is significantly delayed. When cattle are treated with a bolus delivering 40 mg ivermectin per kg cow per day, their dung remains intact on grassland for at least three months. The conclusions drawn from the various papers on these effects are compared and contrasted. In particular, attention is drawn to the general failure to recognize the importance of delayed reactions to non-lethal doses of avermectins, and to our lack of consideration of long-term consequences for cow-pat insects and the wider implications for ecology.

“…Reductions can be beneficial by reducing populations of pestiferous insects that breed in dung (Miller et al, 1981;Schmidt, 1983;Fincher, 1992). However, reduced insect activity (i.e.…”

Section: Introductionmentioning

confidence: 99%

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

Floate

1998

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.