The development and survival of three species of coprophagous insect after feeding on the faeces of sheep treated with controlled-release formulations of ivermectin or albendazole.
OBJECTIVE
To assess the toxicity from residues of controlled-release formulations of ivermectin and albendazole to insects that feed on sheep faeces.


METHODS
In two consecutive years, groups of sheep were treated with controlled-release capsules of ivermectin or albendazole. Untreated sheep were used as controls.


METHODS
Larvae of the bush fly, Musca vetustissima, and adults and larvae of the dung beetles, Onthophagus taurus and Euoniticellus fulvus were fed on faeces collected at intervals after drug treatment. In assays using beetles, treatment effects were assessed by comparing numbers of eggs laid, survival of juveniles and survival of mature and immature adults. Survival at time of pupariation was used in assays on flies.


CONCLUSIONS
Faeces from sheep treated with albendazole had no detectable effects on breeding by either flies or beetles. In contrast, faeces voided by sheep treated with controlled-release capsules of ivermectin (CRI) precluded successful breeding by each of the species tested. No fly larvae and almost no beetle larvae survived in faeces collected up to 39 days after capsule administration. Newly-emerged O taurus also suffered significant mortality whereas those that survived underwent delayed sexual maturation. Ivermectin residues had no effect on the survival of sexually mature beetles, but reduced the fecundity of O taurus. A model simulating the effects of drug residues on dung beetle populations indicates that CRIs have the potential to cause substantial declines in beetle numbers, particularly if treatment coincides with spring emergence.
CSIRO Entomology, GPO Box 1700, Canberra, Australian Capital Territory 2601.
K G
KG
Wardhaugh
P
P
Holter
B
B
Longstaff
D015766:Albendazole / Q000494:pharmacology* / Q000627:therapeutic use; D000704:Analysis of Variance; D000818:Animals; D003692:Delayed-Action Preparations; D004305:Dose-Response Relationship, Drug; D004350:Drug Residues / Q000032:analysis; D005243:Feces / Q000469:parasitology; D007313:Insecta / Q000187:drug effects / Q000254:growth & development*; D007306:Insecticides / Q000494:pharmacology* / Q000627:therapeutic use; D007559:Ivermectin / Q000494:pharmacology* / Q000627:therapeutic use; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D009198:Myiasis / Q000517:prevention & control / Q000662:veterinary*; D012756:Sheep; D012757:Sheep Diseases / Q000517:prevention & control*
D003692:Delayed-Action Preparations; D007306:Insecticides; D007559:Ivermectin; D015766:Albendazole