An in vitro larval immersion microassay for identifying and characterizing candidate acaricides.
We have optimized a larval immersion microassay (LIM) that offers superior sensitivity, flexibility to accommodate multiple formulations, and a robust capability for rapidly screening many compounds with a minimal requirement of test article for evaluation. Dose-response studies were conducted for representative members from the organophosphate, pyrethroid, pyrazole, carbamate, macrocyclic lactone, and formamidine chemistries against Amblyomma americanum (L.). Time-response experiments revealed that permethrin was the most rapid acting, whereas fipronil had the slowest speed-of-kill against A. americanum. Comparison of drug susceptibility profiles between multiple ixodid ticks suggests that A. americanum is an effective model for predicting compound potency against Boophilus spp. in this bioassay. The LIM is suitable for the identification and characterization of active molecules from small- and medium-sized compound or natural product libraries, and it can be a useful tool to prioritize molecules for further in vivo testing in animal models.
White
W Hunter
WH
Elanco Animal Health Research and Development, A Division of Eli Lilly & Co, Greenfield, IN 46140, USA.
Plummer
Philip R
PR
Kemper
Connie J
CJ
Miller
Robert J
RJ
Davey
Ronald B
RB
Kemp
David H
DH
Hughes
Suzanne
S
Smith
Charles K
CK
Gutierrez
Jesus A
JA
D000818:Animals; D001681:Biological Assay / Q000379:methods; D004390:Chlorpyrifos; D007300:Insect Control / Q000379:methods*; D007306:Insecticides / Q000145:classification / Q000633:toxicity*; D007814:Larva / Q000187:drug effects; D026023:Permethrin; D011720:Pyrazoles; D013987:Ticks / Q000254:growth & development*
D007306:Insecticides; D011720:Pyrazoles; D026023:Permethrin; D004390:Chlorpyrifos; C082360:fipronil