Assessment of toxicity and potential risk of the anticoagulant rodenticide diphacinone using Eastern screech-owls (Megascops asio).
In the United States, new regulatory restrictions have been placed on the use of some second-generation anticoagulant rodenticides. This action may be offset by expanded use of first-generation compounds (e.g., diphacinone; DPN). Single-day acute oral exposure of adult Eastern screech-owls (Megascops asio) to DPN evoked overt signs of intoxication, coagulopathy, histopathological lesions (e.g., hemorrhage, hepatocellular vacuolation), and/or lethality at doses as low as 130 mg/kg body weight, although there was no dose-response relation. However, this single-day exposure protocol does not mimic the multiple-day field exposures required to cause mortality in rodent pest species and non-target birds and mammals. In 7-day feeding trials, similar toxic effects were observed in owls fed diets containing 2.15, 9.55 or 22.6 ppm DPN, but at a small fraction (<5%) of the acute oral dose. In the dietary trial, the average lowest-observed-adverse-effect-level for prolonged clotting time was 1.68 mg DPN/kg owl/week (0.24 mg/kg owl/day; 0.049 mg/owl/day) and the lowest lethal dose was 5.75 mg DPN/kg owl/week (0.82 mg/kg owl/day). In this feeding trial, DPN concentration in liver ranged from 0.473 to 2.21 μg/g wet weight, and was directly related to the daily and cumulative dose consumed by each owl. A probabilistic risk assessment indicated that daily exposure to as little as 3-5 g of liver from DPN-poisoned rodents for 7 days could result in prolonged clotting time in the endangered Hawaiian short-eared owl (Asio flammeus sandwichensis) and Hawaiian hawk (Buteo solitarius), and daily exposure to greater quantities (9-13 g of liver) could result in low-level mortality. These findings can assist natural resource managers in weighing the costs and benefits of anticoagulant rodenticide use in pest control and eradication programs.
Patuxent Wildlife Research Center, US Geological Survey, c/o Beltsville Agricultural Research Center-East, Building 308 10300 Baltimore Avenue, Beltsville, MD 20705, USA. brattner@usgs.gov
Barnett A
BA
Rattner
Katherine E
KE
Horak
Rebecca S
RS
Lazarus
Karen M
KM
Eisenreich
Carol U
CU
Meteyer
Steven F
SF
Volker
Christopher M
CM
Campton
John D
JD
Eisemann
John J
JJ
Johnston
D000284:Administration, Oral; D000818:Animals; D000925:Anticoagulants / Q000493:pharmacokinetics / Q000633:toxicity*; D056486:Chemical and Drug Induced Liver Injury / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D003362:Cost-Benefit Analysis; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008136:Longevity / Q000187:drug effects; D008297:Male; D010630:Phenindione / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000633:toxicity; D012378:Rodenticides / Q000493:pharmacokinetics / Q000633:toxicity*; D013045:Species Specificity; D020305:Strigiformes / Q000502:physiology*; D018675:Toxicity Tests; D014914:Whole Blood Coagulation Time
D000925:Anticoagulants; D012378:Rodenticides; C100262:diphenadione; D010630:Phenindione