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Comparative effects of abamectin and two formulations of ivermectin on the survival of larvae of a dung‐breeding fly
Author(s) -
WARDHAUGH KG,
MAHON RJ
Publication year - 1998
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.1998.tb10158.x
Subject(s) - ivermectin , abamectin , feces , biology , larva , bioassay , myiasis , veterinary medicine , toxicology , zoology , pesticide , agronomy , ecology , medicine
Objectives To compare the survival of larvae of a dung‐breeding fly in the faeces of cattle treated either with an injectable formulation of abamectin, or with oral or injectable formulations of ivermectin. Design Replicated bioassays were conducted on larvae of the bush fly, Musca vetustissima, using faeces collected before and at intervals after drug treatment. Animals Two cows and their calves were allocated to each of three drug treatments and dosed according to individual weights. Procedures Differences in the proportions of larvae pupariating were used as measures of the toxicity of drug residues. Results Development of fly larvae was inhibited in all faeces collected 1 to 4 days after treatment. In cattle treated with oral ivermectin, there was reduced larval survival in faeces collected 8 and 16 days after treatment, but by day 32, survival was equivalent to that recorded in the faeces of untreated cattle. With injectable ivermectin, there was no survival at day 8, limited survival at day 16 and, at day 32, survival was not significantly affected. With injectable abamectin, survival was completely suppressed until day 32, at which time the number of pupariating larvae did not differ significantly from that recorded in faeces from untreated animals. Conclusion The oral formulation of ivermectin is eliminated more rapidly than the injectable formulation and, as a consequence, is likely to be less harmful to dung‐feeding insects. Abamectin and ivermectin appear to equally toxic larvae of M vetustissima.