Spinosad is a naturally-occurring insecticide found in the the soil bacterium S. spinosa.1 It is a mixture of the macrocyclic lactones spinosyn A and spinosyn D , which act as agonists of insect nicotinic acetylcholinesterase receptors (nAChRs). Oral administration of spinosad induces toxicity in fruit flies including C. capitata, B. curcurbitae, and B. dorsalis (LC50s = 2.8-4.2, 4.3-5.5, and 3.1-3.3 µg/ml, respectively) but has low toxicity in vertebrates.2,3,4 It also inhibits canine P-glycoprotein (P-gp; IC50 = 0.2 µg/ml).5 Formulations containing spinosad have been used in the agricultural and veterinary control of insects.

[1] Vo, D.T., Hsu, W.H., Abu-Basha, E.A., et al.Insect nicotinic acetylcholine receptor agonists as flea adulticides in small animalsJ. Vet. Pharmacol. Ther.33(4)315-322(2010)

[2] Stark, J.D., Vargas, R., and Miller, N.Toxicity of spinosad in protein bait to three economically important tephritid fruit fly species (Diptera: Tephritidae) and their parasitoids (Hymenoptera: Braconidae).J. Econ. Entomol.97(3)911-915(2004)

[3] SÁnchez-Bayo, F.Insecticides mode of action in relation to their toxicity to non-target organismsJ. Environ. Anal. Toxicol.S4:002(2012)

[4] Amaral, T.S., Carvalho, T.F., Silva, M.C., et al.Short-term effects of a spinosyn's family insecticide on energy metabolism and liver morphology in frugivorous bats Artibeus lituratus (Olfers, 1818)Braz. J. Biol.72(2)299-304(2012)