Indirect contamination of cockroaches by anticoagulant rodenticides

Abstract

The wide use of anticoagulant rodenticides for rat control has led to indirect poisoning of non-target birds, mammals, and vertebrates by anticoagulant rodenticides, yet contamination of insects is poorly known. We studied the behavior of two cockroach species feeding on commercial rodenticide bait formulations under laboratory conditions. Rodenticides comprised brodifacoum, difenacoum, and bromadiolone. We measured bait uptake by cockroaches, mortality, and their anticoagulant rodenticide body burden after 21 days of exposure. Results show that rodenticide residue levels in cockroaches ranged between 0.01 and 1.32 ± 0.15 µg/g dry weight. No mortality associated with rodenticide bait consumption was observed over a 21 days exposure period. Cockroaches consumed up to 50% of offered bait when attracted by this formulation, otherwise close to none. Overall, insects such as cockroaches may contribute to the environmental spread of anticoagulant rodenticides.