Secondary poisoning in the common shrew (Sorex araneus) fed earthworms exposed to an organophosphate pesticide

Earthworms Esinia spp. were kept for a 48-h period in artificial soil contaminated with a sublethal dose of dimethoate, an organophosphate pesticide. Different groups of common shrews, Sorex araneus, were fed earthworms that had been exposed to contaminated soil either 1, 5, or 10 d previously. Cholinesterase (ChE) activity was measured in worms and in the shrews before and after they were fed contaminated worms. After exposure to dimethoate-treated soil, ChE activity in worms was inhibited by 90%. Recovery was slow, and ChE activity was still markedly inhibited (35% of the control level) 40 d after exposure. Whole blood ChE activity in shrews was significantly depressed (64% of preexposure levels) when animals were fed worms that had been exposed to dimethoate-treated soil on the previous day. There was no such significant inhibition in shrews fed worms that had been exposed to contaminated soil either 5 or 10 d previously.