Mosquitocidal activity and mode of action of the isoxazoline fluralaner

Authors: JIANG, SHIYAO - University Of Florida; TSIKOLIA, MAIA - University Of Florida; Bernier, Ulrich; BLOOMQUIST, JEFFREY - University Of Florida

Submitted to: International Journal of Environmental Research and Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2017
Publication Date: 2/6/2017
Citation: Jiang, S., Tsikolia, M., Bernier, U.R., Bloomquist, J.R. 2017. Mosquitocidal activity and mode of action of the isoxazoline fluralaner. International Journal of Environmental Research and Public Health. 14(2):154. https://doi.org/10.3390/ijerph14020154.
DOI: https://doi.org/10.3390/ijerph14020154

Interpretive Summary: Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology and University of Florida to evaluate a chemical used mainly for flea control in dogs. The active chemical in the flea control pill is called fluralaner. It is from a newer class of chemicals that are effective against pests that have developed resistances to commonly used insecticides. In this study, fluralaner was evaluated for it's ability to kill mosquitoes. The results of the study indicate that this compound is not very effective against mosquitoes in studies where the mosquitoes come in direct contact with the chemical. This study shows that this chemical in it's present form is not a good candidate for use in mosquito control. The results of this study benefit researchers and mosquito control professionals who conduct mosquito control using chemicals.

Technical Abstract: Mosquitoes, such as Aedes aegypti and Anopheles gambiae, are important vectors of human diseases. Fluralaner, a recently introduced parasiticide, was evaluated as a mosquitocide in this study.On Ae. aegypti and An. gambiae fourth-instar larvae, fluralaner had 24-h LC50 (lethal concentration for 50% mortality) values of 1.8 ppb and 0.4 ppb, respectively. Following topical application to adult Ae. aegypti, fluralaner toxicity reached a plateau in about 3 days, with 1- and 3-day LD50 (lethal dose for 50% mortality) values of 1.3 ng/mg and 0.26 ng/mg, suggesting a slowly developing toxicity. Fipronil outperformed fluralaner by up to 100-fold in adult topical, glass contact, and feeding assays on Ae. aegypti. These data show that fluralaner does not have exceptional toxicity to mosquitoes in typical exposure paradigms. In electrophysiological recordings on Drosophila melanogaster larval central nervous system, the effectiveness of fluralaner for restoring nerve firing after gamma-aminobutyric acid (GABA) treatment, a measure of GABA antagonism, was similar in susceptible Oregon-R and cyclodiene-resistant rdl-1675 strains, with EC50 (half maximal effective concentration) values of 0.34 µM and 0.29 µM. Although this finding suggests low cross resistance in the presence of rdl, the moderate potency, low contact activity, and slow action of fluralaner argue against its use as an adult mosquitocide for vector control.