Extinosad contains the active ingredient, spinosad, which is derived from the naturally-occurring soil bacterium, Saccharopolyspora spinosa. Once absorbed or ingested by target insects, spinosad causes prolonged involuntary muscle contractions and tremors, resulting in paralysis and death. Spinosad has a high level of activity against a number of insect species, including the sheep body louse (Bovicola ovis) and the sheep blowfly (Lucilia cuprina) and its larvae. Spinosad is chemically unrelated to any other compound used in the Australian livestock industry.