[Analysis of bromadiolone (an anticoagulant rodenticide) in plasma, liver and kidney of the rat]

Determination of bromadiolone residues in fox faeces by LC/ESI-MS in relationship with toxicological data and clinical signs after repeated exposure

In many countries, the fox (Vulpes vulpes), predator of small mammals, is particularly affected by anticoagulant rodenticides such as bromadiolone due to secondary poisoning. Nevertheless, to date, no method of exposure monitoring is applicable in the field over large areas, and no toxicological data are available concerning sensitivity of foxes to bromadiolone. The aim of this work was to compare excretion kinetics of bromadiolone in fox faeces with clinical and haemostatic effects after repeated exposure to intoxicated voles. A sensitive method for the quantification of bromadiolone excretion in fox faeces and plasma was developed, using liquid chromatography combined with electrospray ionisation mass spectrometry (LC/ESI-MS). The LoD was 0.9microg/kg and 0.15microg/L, and the LoQ was 3.0microg/kg and 0.5microg/L, in faeces and in plasma, respectively. Four captive foxes were fed for 2 or 5 days with water voles (Arvicola terrestris Sherman) spiked with bromadiolone at concentrations close to those measured in the field. Faeces and blood were collected for bromadiolone titration, and blood-clotting tests were performed to monitor fox health daily during 10 days and then every 3-4 days until the end of the experiment (D28). Then, after euthanasia, a complete necropsy was performed, and levels of bromadiolone residues in the liver were determined. Bromadiolone residues were detected in faeces 15h after the first exposure. They increased dramatically during the exposure period and then gradually decreased, but they remained detectable at the end of the experiment, i.e., 26 days after the last exposure. Bromadiolone residues in plasma showed a similar pattern but were no longer detectable 7-24 days after the last exposure. Two foxes presented very severe external haemorrhages, requiring the administration of the antidote vitamin-K1. Bromadiolone residues in faeces and their relationships with exposure and other direct-markers that were measured are discussed. Liver residues and the toxicity data of our study will help to interpret data from fox carcasses collected by wildlife disease surveillance networks. These findings provide a basis for programs aiming to monitor the exposure of wild fox populations to bromadiolone using non-invasive methods based on standard sampling and analysis of residues in faeces.

Rodenticides

Rodenticides are second only to insecticides in the prevalence of pesticide exposure. Hundreds of rodenticide products currently exist, yet only a handful of them are involved in most toxicoses of companion animals. The most commonly reported toxicoses in the United States are those caused by anticoagulant rodenticides, bromethalin, cholecalciferol, strychnine, and zinc phosphide. The pathophysiologic findings, diagnosis, and treatment of each of these five rodenticides are discussed.

Detection of anticoagulant rodenticides (4-hydroxycoumarins) by thin-layer chromatography and reversed-phase high-performance liquid chromatography with fluorescence detection

The detection of 4-hydroxycoumarin rodenticides in poisoned domestic animals requires a highly sensitive method as tissue and serum levels of anticoagulants may be very low owing to rapid elimination, metabolism or post-mortem degradation. Thin-layer chromatography (TLC) and reversed-phase high-performance liquid chromatography (RP-HPLC) with fluorescence detection were used to identify the anticoagulants in spiked tissues and in suspicious samples. The analysis of ten suspicious samples highlighted the limitations of both methods. Only the three samples of baits were found positive by TLC whereas one of the five anticoagulants was detected in eight samples by RP-HPLC with fluorescence detection. Therefore, RP-HPLC with fluorescence detection proved to be the more sensitive method for detecting low levels of 4-hydroxycoumarins in blood serum, liver and ingesta, whereas TLC is usually sufficient for analysing baits.

Determination of diastereoisomers of bromadiolone, an anticoagulant rodenticide, in animal tissues by high-performance liquid chromatography

Two components isolated by semi-preparative normal phase high-performance liquid chromatography (HPLC) of bromadiolone reference material were tentatively identified as diastereoisomeric forms. Examination by mass spectroscopy confirmed this identification and supporting evidence was provided by identical UV fluorescence characteristics. The separated isomers were used to examine the chromatographic properties of bromadiolone in ion-pair, ion-suppression and weak ion-exchange HPLC modes. Conditions suitable for the analytical determination of the individual diastereoisomers were established for each mode. The influence of mobile phase pH on the resolution of coumarin-based rodenticides by weak ion-exchange HPLC on an aminopropyl-bonded phase was studied. Clean-up techniques for the determination of residues of bromadiolone in animal tissue extracts were compared. A combined gel permeation and adsorption chromatographic procedure was preferred for sensitive assay; it permitted the use of either fluorescence or UV detection. The lower practical limit of determination of each isomer in animal tissues was 0.005 mg kg-1 using UV detection and 0.0005 mg kg-1 using fluorescence detection.

Kinetics of bromadiolone, anticoagulant rodenticide, in the Norway rat (Rattus norvegicus)

Rats (Rattus norvegicus) dosed orally with the rodenticide bromadiolone (0.8 and 3 mg/kg) were sacrificed in groups of 4 rats at various times up to 97 hours after administration. Bromadiolone was assayed in plasma, liver and kidney by an HPLC method. The compound disappeared slowly from the organism with a half-life of 25.7 hours for the 0.8 mg/kg dose and 57.5 hours for the 3 mg/kg. Concentrations in liver were rapidly established and were 14- to 46-fold higher than plasma concentrations. 97 hours after 3 mg/kg dose, liver concentrations were about 1.5 micrograms/g. Bromadiolone levels in kidney were slightly higher than those observed in plasma, with a longer half-life.