Poisoning by Anticoagulant Rodenticides in Humans and Animals: Causes and Consequences

Anticoagulant rodenticides (ARs) are a keystone of the management of rodent populations in the world. The widespread use of these molecules raises questions on exposure and intoxication risks, which define the safety of these products. Exposures and intoxications can affect humans, domestic animals and wildlife. Consequences are different for each group, from the simple issue of intoxication in humans to public health concern if farm animals are exposed. After a rapid presentation of the mechanism of action and the use of anticoagulant rodenticides, this chapter assesses the prominence of poisoning by anticoagulant rodenticides in humans, domestic animals and wildlife

Enantiomeric fraction evaluation of the four stereoisomers of difethialone in biological matrices of rat by two enantioselective liquid chromatography tandem mass spectrometry methods: Chiral stationary phase or derivatization

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Anticoagulant Rodenticides: Resistance and Residues in Norway Rats in France

In the European Union (EU), anticoagulant rodenticides (AR) represent more than 90% of the commercially available products for use against commensal rodents. The only other active ingredients (CO2, chloralose, corn cob) represent minor alternatives. A major issue in the EU is the resistance level of rat and mice populations, as well as potential non-target species exposure. This study presents results of surveys of anticoagulant resistance in Norway rats based on the sequencing of the VKORC1 gene, the major gene involved in AR and an investigation of the presence of AR residues detected in rodents trapped alive in urban and rural areas in order to investigate the potential risk of secondary poisoning of predators and scavengers. For resistance monitoring, rats were either trapped alive in the city of Lyon or its surroundings, or alternatively rat tails were obtained from pest control operators from France. Specific DNA primers were used for DNA sequencing and mutation identifications. AR residues were monitored by LC-MS-MS (for the 8 ARs marketed in Europe), with a limit of quantification of 1.0 µg/kg in liver samples. AR resistance appears to be extremely common (45-70% of all rats tested, depending on the part of France), with the notable exception of downtown Lyon where all rats are susceptible to AR. AR residues are detected in almost 100% of the rats trapped and tested (>200 individuals in/around Lyon). These results show that resistance is common in France, and evidence from neighboring countries suggests that this is an EU-wide problem. More surprising is the fact that all rodents tested contain detectable residues of AR, which could potentially result in secondary poisoning

Stereochemistry: a tool to modify pharmacokinetics properties of anticoagulant rodenticides without modifying their efficiency

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Mass spectrometry characterization of anticoagulant rodenticides and hydroxyl metabolites

International audienceRationaleAnticoagulant rodenticides (ARs) are used worldwide for rodent population control to protect human health and biodiversity, and to prevent agricultural and economic losses. Rodents may develop a metabolic resistance to ARs. In order to help understand such metabolic resistance, mass spectrometry was used to position the hydroxylated group of hydroxyl metabolites of second‐generation ARs (SGARs).MethodsMost AR pesticides are derived from the 4‐hydroxycoumarin/thiocoumarin family. We used low‐resolution and high‐resolution mass spectrometry to understand the fragmentation pathways of the ARs and their respective metabolites, and to better define the structure of their tandem mass spectrometry product ions.ResultsSeven specific product ions were evidenced for five ARs, with their respective chemical structures. Those ions were obtained as well from the mass spectra of the hydroxyl metabolites of four SGARs, difenacoum (DFM), brodifacoum (BFM), difethialone (DFTL) and flocoumafen (FLO), with different positions of the hydroxyl group.ConclusionsThe differences in chemical structure between DFM on the one hand and BFM, FLO and DFTL on the other could explain the differences in bioavailability between these two groups of molecules. The defined product ions will be used to investigate the part played by the metabolic issue in the field resistance of SGARs

Anticoagulant Rodenticides: Resistance and Residues in Norway Rats in France

In the European Union (EU), anticoagulant rodenticides (AR) represent more than 90% of the commercially available products for use against commensal rodents. The only other active ingredients (CO2, chloralose, corn cob) represent minor alternatives. A major issue in the EU is the resistance level of rat and mice populations, as well as potential non-target species exposure. This study presents results of surveys of anticoagulant resistance in Norway rats based on the sequencing of the VKORC1 gene, the major gene involved in AR and an investigation of the presence of AR residues detected in rodents trapped alive in urban and rural areas in order to investigate the potential risk of secondary poisoning of predators and scavengers. For resistance monitoring, rats were either trapped alive in the city of Lyon or its surroundings, or alternatively rat tails were obtained from pest control operators from France. Specific DNA primers were used for DNA sequencing and mutation identifications. AR residues were monitored by LC-MS-MS (for the 8 ARs marketed in Europe), with a limit of quantification of 1.0 µg/kg in liver samples. AR resistance appears to be extremely common (45-70% of all rats tested, depending on the part of France), with the notable exception of downtown Lyon where all rats are susceptible to AR. AR residues are detected in almost 100% of the rats trapped and tested (>200 individuals in/around Lyon). These results show that resistance is common in France, and evidence from neighboring countries suggests that this is an EU-wide problem. More surprising is the fact that all rodents tested contain detectable residues of AR, which could potentially result in secondary poisoning

Mass spectrometry characterization of anticoagulant rodenticides and hydroxyl metabolites

International audienceRationaleAnticoagulant rodenticides (ARs) are used worldwide for rodent population control to protect human health and biodiversity, and to prevent agricultural and economic losses. Rodents may develop a metabolic resistance to ARs. In order to help understand such metabolic resistance, mass spectrometry was used to position the hydroxylated group of hydroxyl metabolites of second‐generation ARs (SGARs).MethodsMost AR pesticides are derived from the 4‐hydroxycoumarin/thiocoumarin family. We used low‐resolution and high‐resolution mass spectrometry to understand the fragmentation pathways of the ARs and their respective metabolites, and to better define the structure of their tandem mass spectrometry product ions.ResultsSeven specific product ions were evidenced for five ARs, with their respective chemical structures. Those ions were obtained as well from the mass spectra of the hydroxyl metabolites of four SGARs, difenacoum (DFM), brodifacoum (BFM), difethialone (DFTL) and flocoumafen (FLO), with different positions of the hydroxyl group.ConclusionsThe differences in chemical structure between DFM on the one hand and BFM, FLO and DFTL on the other could explain the differences in bioavailability between these two groups of molecules. The defined product ions will be used to investigate the part played by the metabolic issue in the field resistance of SGARs

Determination of Water Droplet Size Distributions by Low Resolution PFG-NMR

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Liver and fecal samples suggest differential exposure of red fox (Vulpes vulpes) to trans- and cis-bromadiolone in areas from France treated with plant protection products

International audienceBromadiolone, a second generation anticoagulant rodenticide (SGARs), is authorized in France to control water voles (Arvicola scherman) outbreaks. SGARs enter the food chain and their persistence in rodents is responsible for secondary exposure or poisoning of predators and scavengers. Bromadiolone commercial formulations are a mixture of two diastereoisomers of bromadiolone: 70-90% is trans-bromadiolone and 10-30% is cis-bromadiolone. Both diastereoisomers were reported to inhibit coagulation function with similar potency. On the other hand, cis-bromadiolone has been shown to be less tissue-persistent than trans-bromadiolone in rats. Furthermore, cis-bromadiolone was not found in liver of red kites after bromadiolone poisonings of water voles. In this study, amulti-residue LC-MS/MS method for the quantification of the diastereoisomers of SGARs was used to investigate their proportions in field samples of another vole's predator, the red fox. Red fox livers (n = 48) and scats (n = 160) were collected in a pesticide use zone within a few months of bromadiolone application. We reported the concentrations of bromadiolone diastereoisomers in the livers and scats. Accumulation of bromadiolone was apparent in 81% (n = 39) of the livers with mean and max concentrations of 355 and 2060 ng/g, and in 23% of the faeces with mean and max concentrations of 78.5 and 593 ng/g. However, cis-bromadiolone was not detected in the liver of 35 of 39 exposed red foxes and was present at very low concentrations (below 24.6 ng/g) in 4 of 39 exposed red foxes. It was not detected in 11 of the positive scats and represented only 4.2% of the bromadiolone residues in scats. This demonstrated differential persistence of trans- and cis-bromadiolone in the food chain. The results suggest that a change of the proportions of bromadiolone diastereoisomers in baits could reduce the risk of secondary poisoning of predators, but retain primary toxicity for control water voles outbreaks

Bioaccumulation of chlorophacinone in strains of rats resistant to anticoagulants

International audienceBACKGROUND: Anticoagulants are the only available compounds in the EU to control rat populations. Resistance to anticoagulant rodenticides (antivitamin K or AVK) is described and widespread across Europe. The present objective was to determine whether resistance was associated with an increased potential for bioaccumulation of AVK in the liver. Rats were selected from three major resistant genetically identified strains across Europe: Y139C (Germany), Y139F (France) and L120Q (United Kingdom). The rats were housed in individual cages and fed chlorophacinone wheat bait (50 mg kg1). Animals were assigned to groups for euthanasia either on day 1, 4, 9 or 14 (resistant rats) or on days 1 and 4 (susceptible rats). RESULTS: Chlorophacinone accumulated from day 1 to day 4 in all strains (maximum 160 mu g liver1) and remained stable thereafter. There was no significant difference between strains. Extensive metabolism of chlorophacinone was also found, and was similar (in nature and proportion of metabolites) across strains (3 OH-metabolites identified). Only the survival time differed significantly (L120Q > Y139C = Y139F > susceptible). CONCLUSIONS: Accumulation of chlorophacinone occurs from day 1 to day 4, and an equilibrium is reached, suggesting rapid elimination. Resistant and susceptible rats accumulate chlorophacinone to the same extent and only differ in terms of survival times. Resistant rats may then be a threat for non-target species for prolonged periods of time