Effects of ivermectin on target and non-target dung-breeding flies (Diptera) in cattle dung pats

Abstract

The effects of antiparasitic drug, ivermectin, on the dung-breeding fiies were studied in laboratory and field experiments in Hokkaido, Japan. In two pour-on treatments (500 geg/kg), ivermectin was excreted in dung for up to 14 and 21 days after treatment, with peaks at 3 days and 1 day, respectively. Dung from treated cattle prevented the larval development of Htzematobia im"tans and AJeomyia cornicina up to 14 days and reduced the larval and pupal survival rates at 21 days after treatment. In the field experiment using emergence traps, the numbers of emerged flies frorn dung pats were 3,655 {18 families) in control dung and 2,234 {16 families) in treated dung. Especially, Musca bezzii, Ravinia striata, Sepsis duplicata, Sopsis thora- cica, Sopsis cynipsea, Sphaeroceridea, Empididae, Sciaridae and Chironomidae were severely reduced in treated dung, Reduction of cyclorrhaphaous flies similarly occur- red at 1, 3 and 7 days after treatment, which coincides with high concentrations of ivermectin. Conversely, Ceratopogonidae and Phoridae increased in treated dung, regardless of days (1, 3 and 7) after treatment Dry weights of fiies emerged from dung pats of treated cattle in the field experiment were only 5.8% of those from dung of control cattle, indicating that dung-decomposing activity by fiy larvae was supressed in dung of treated cattle,