Third instar nymphs of Rhodnius prolixus exposed to alpha-cyanopyrethroids: From hyperactivity to death

The hyperactivity, incoordination, recovery, and mortality produced by four alpha -cyanopyrethroids usually used for Chagas disease vector control (be ta -cypermethrin, beta -cyfluthrin, lambda -cyhalothrin, and deltamethrin) were evaluated on third instar nymphs of Rhodnius prolixus. All pyrethroids modified the locomotor activity of the nymphs, which increased Linearly as a function of the log of insecticide concentration, lambda -Cyhalothrin sh owed the lowest values of Effective Concentration 50%, Lethal Concentration 50%, Effective Time 50%, and Lethal Time 50% when insecticides were applie d by contact with treated filter papers. Recovery from incoordination was o bserved after topical application of the insecticides. The recovery was inh ibited by the simultaneous application of piperonyl butoxide, suggesting th at biotransformation by mixed-function microsomal oxidases is involved in t he process of recovery. (C) 2001 Wiley-Liss, Inc.