New Rodenticide on the Block: Diagnosing Bromethalin Intoxication in Wildlife

Abstract

Bromethalin is being used more widely for commensal rodent control because of increased regulation on second-generation anticoagulant rodenticides. Wildlife losses in California are tracked by the California Department of Fish and Wildlife. Bromethalin is a neurotoxicant which is not thought to cause secondary poisoning. From August 2014 to January 2016, 24 cases of bromethalin intoxication were investigated in California. These include 11 raccoons, 11 striped skunks, one gray fox, and one fox squirrel. Most of these occurred in Marin County, where active surveillance of wildlife for rodenticide exposure is occurring. Bromethalin exposure should be evaluated when a wild animal that may have accessed bait is showing neurological signs. Trauma and distemper should be ruled out. Histological changes may be found in the central nervous system but are not always present. The tissue of choice for toxicological analysis is adipose. It is likely that bromethalin intoxication is under-reported in the rest of the state and may be mistaken for distemper infection or trauma. Primary exposure of wildlife to bromethalin could be prevented by placing baits in tamper-resistant bait stations.