Monitoring agricultural rodenticide use and secondary exposure of raptors in Scotland

Significant Turning Point: Common Buzzard (Buteo buteo) Exposure to Second-Generation Anticoagulant Rodenticides in the United Kingdom

Second-generation anticoagulant rodenticides (SGARs) are widely used to control rodent populations, resulting in the serious secondary exposure of predators to these contaminants. In the United Kingdom (UK), professional use and purchase of SGARs were revised in the 2010s. Certain highly toxic SGARs have been authorized since then to be used outdoors around buildings as resistance-breaking chemicals under risk mitigation procedures. However, it is still uncertain whether and how these regulatory changes have influenced the secondary exposure of birds of prey to SGARs. Based on biomonitoring of the UK Common Buzzard (Buteo buteo) collected from 2001 to 2019, we assessed the temporal trend of exposure to SGARs and statistically determined potential turning points. The magnitude of difenacoum decreased over time with a seasonal fluctuation, while the magnitude and prevalence of more toxic brodifacoum, authorized to be used outdoors around buildings after the regulatory changes, increased. The summer of 2016 was statistically identified as a turning point for exposure to brodifacoum and summed SGARs that increased after this point. This time point coincided with the aforementioned regulatory changes. Our findings suggest a possible shift in SGAR use to brodifacoum from difenacoum over the decades, which may pose higher risks of impacts on wildlife.

Active monitoring of long-eared owl (Asio otus) nestlings reveals widespread exposure to anticoagulant rodenticides across different agricultural landscapes

The widespread use of anticoagulant rodenticides (ARs) poses a worldwide threat to farmland wildlife. These compounds accumulate in tissues of both target and non-target species, potentially endangering both direct consumers and their predators. However, investigations on ARs in blood of free-ranging predatory birds are rare. Here, the long-eared owl (Asio otus) has been used as a model predator to assess AR exposure in different agricultural landscapes from a Mediterranean semiarid region. A total of 69 owlets from 38 nests were blood-sampled over 2021 and 2022, aiming to detect AR residues and explore factors that determine their exposure, such as land uses. In addition, prothrombin time (PT) test was conducted to assess potential effects of AR contamination. Overall, nearly all the samples (98.6 %) tested positive for at least one compound and multiple ARs were found in most of the individuals (82.6 %). Among the ARs detected, flocoumafen was the most common compound (88.4 % of the samples). AR total concentration (ΣARs) in blood ranged from 0.06 to 34.18 ng mL-1, detecting the highest levels in the most intensively cultivated area. The analysis of owl pellets from 19 breeding territories showed relevant among-site differences in the contribution of rodents and birds into the diet of long-eared owls, supporting its high dietary plasticity and indicating AR presence at multiple trophic levels. Moreover, a positive and significant correlation was found between ΣARs and PT (Rho = 0.547, p < 0.001), which demonstrates the direct effect of ARs on free-living nestlings. Our results provide a preliminary overview of AR exposure in a little-studied owl species inhabiting agricultural and rural landscapes. Despite the low detected levels, these findings indicate widespread exposure -often to multiple compounds- from early life stages, which raises concern and draws attention to an ongoing and unresolved contamination issue.

Evaluation of anticoagulant rodenticide sensitivity by examining in vivo and in vitro responses in avian species, focusing on raptors

Anticoagulant rodenticides (ARs) are used to control pest rodent species but can result in secondary poisoning of non-target animals, especially raptors. In the present study, differences in AR sensitivity among avian species were evaluated by comparing in vivo warfarin pharmacokinetics and effects, measuring cytochrome P450s (CYPs) expression involved in AR metabolism, and conducting in vitro inhibition assays of the AR target enzyme Vitamin K 2,3-epoxide reductase (VKOR). Oral administration of warfarin at 4 mg/kg body weight did not prolong prothrombin time in chickens (Gallus gallus), rock pigeons (Columba livia), or Eastern buzzards (Buteo japonicus). Rock pigeons and buzzards exhibited shorter plasma half-life of warfarin compared to chickens. For the metabolite analysis, 4'-hydroxywarfarin was predominantly detected in all birds, while 10-hydroxywarfarin was only found in pigeons and raptors, indicating interspecific differences in AR metabolism among birds likely due to differential expression of CYP enzymes involved in the metabolism of ARs and variation of VKOR activities among these avian species. The present findings, and results of our earlier investigations, demonstrate pronounced differences in AR sensitivity and pharmacokinetics among bird species, and in particular raptors. While ecological risk assessment and mitigation efforts for ARs have been extensive, AR exposure and adverse effects in predatory and scavenging wildlife continues. Toxicokinetic and toxicodynamic data will assist in such risk assessments and mitigation efforts.

State of the art, gaps and future perspectives on common kestrel ecotoxicology

Anthropogenic activities have caused a steady decline of common kestrel (Falco tinnunculus) since the 1980 s. Effects, especially sublethal effects of contaminants, need to be investigated to ensure the conservation of this species. Data about countries, biological material, contaminants classes, and methodological approaches were collected from scientific publications to highlight gaps on common kestrel toxicology and ecotoxicology. We found that most studies have been conducted in Europe and in the field, underlining a lack of in vitro studies. The studies investigated mainly contaminant levels, while sublethal effects, evaluation of emerging contaminants and use of non-invasive or low-invasive samples were scarce. This work shows important gaps on toxicological status of the common kestrel, highlighting the importance of developing a non-lethal approach that combines responses at different levels of biological organization, as well as data on chemical contamination and on the environment in which the different populations inhabit.

Farmers' perception of the ecosystem services provided by diurnal raptors in arid Rajasthan

Farmers are the most important stakeholders in wildlife conservation in the agricultural landscape. Understanding the farmer's perceptions, attitude, behaviour, and knowledge toward conservation is critical in developing an effective conservation programme in human-dominated landscapes. We conducted semi-structured face-to-face interviews with 373 farmers to understand the farmer's perception of ecosystem services provided by diurnal raptors in the arid region of Rajasthan from July 2020 to February 2021 and from August 2021 to January 2022. We grouped ecosystem services and disservices into larger categories and estimated the correlation between them, finding that disservices are negatively correlated with benefits. Raptors were perceived as beneficial for their role in controlling rodents and pests, but negatively for poultry predation. In addition, we built a binomial generalised linear model with a logit function to better understand the factors that influence farmers' perceptions of raptors (positive or negative). We observed that males and females have different attitudes toward the ecosystem services provided by raptors. It is critical to understand social perceptions in order to conserve species that are rare on a global scale but may face negative perceptions on a local scale. Our study connects ecological information with socio-demographic factors, which can be useful in developing policy measures for raptor conservation.

Diurnal raptors at rescue centres in the Czech Republic: Reasons for admission, outcomes, and length of stay

Rescue centres play an important role in the protection of raptors living in the wild by caring for injured or debilitated animals and abandoned young with the aim of returning them to the wild. A total of 22,538 raptors were admitted to 34 rescue centres in the Czech Republic in the years 2010-2019, with an increasing trend during the monitored period (rSp = 0.7333, p < 0.05). The most frequent reasons for their admission were other injuries and fractures (26.52%), the admission of young (22.98%), and the admission of raptors injured by electric shock injuries (20.51%). It proved possible to release 42.45% of admitted raptors back into the wild, the majority of which (91.05%) were released using the hard-release method. Foster parents were used in 1% of cases and a replacement nest in 0.2% of cases involving the rearing of young. In spite of all the care provided at rescue centres, a total of 39.97% of raptors admitted either died or had to be euthanized. Among them, most raptors were euthanized or died due to injuries caused by collision with a vehicle, electric shock injuries, and other injuries. This generally occurred shortly after admission (a median of two days). The importance of the work of rescue centres lies not merely in returning injured raptors back into the wild (which proves possible in around half of all cases), but also in obtaining information about the factors endangering raptors in the wild and contributing toward a decline in their populations. The findings provide information about human-wildlife interactions in the Czech Republic and their implications for conservation as well as on the effectiveness of rescue centres to successfully treat and subsequently release raptors back into the wild.

Second-generation anticoagulant rodenticides in the blood of obligate and facultative European avian scavengers

The widespread use of second-generation anticoagulant rodenticides (SGARs) and their high persistence in animal tissues has led to these compounds becoming ubiquitous in rodent-predator-scavenger food webs. Exposure to SGARs has usually been investigated in wildlife species found dead, and despite growing evidence of the potential risk of secondary poisoning of predators and scavengers, the current worldwide exposure of free-living scavenging birds to SGARs remains scarcely investigated. We present the first active monitoring of blood SGAR concentrations and prevalence in the four European obligate (i.e., vultures) and facultative (red and black kites) avian scavengers in NE Spain. We analysed 261 free-living birds and detected SGARs in 39.1% (n = 102) of individuals. Both SGAR prevalence and concentrations (ΣSGARs) were related to the age and foraging behaviour of the species studied. Black kites showed the highest prevalence (100%), followed by red kites (66.7%), Egyptian (64.2%), bearded (20.9%), griffon (16.9%) and cinereous (6.3%) vultures. Overall, both the prevalence and average ΣSGARs were higher in non-nestlings than nestlings, and in species such as kites and Egyptian vultures foraging in anthropic landscapes (e.g., landfill sites and livestock farms) and exploiting small/medium-sized carrions. Brodifacoum was most prevalent (28.8%), followed by difenacoum (16.1%), flocoumafen (12.3%) and bromadiolone (7.3%). In SGAR-positive birds, the ΣSGAR (mean ± SE) was 7.52 ± 0.95 ng mL^-1; the highest level detected being 53.50 ng mL^-1. The most abundant diastereomer forms were trans-bromadiolone and flocoumafen, and cis-brodifacoum and difenacoum, showing that lower impact formulations could reduce secondary exposures of non-target species. Our findings suggest that SGARs can bioaccumulate in scavenging birds, showing the potential risk to avian scavenging guilds in Europe and elsewhere. We highlight the need for further studies on the potential adverse effects associated with concentrations of SGARSs in the blood to better interpret active monitoring studies of free-living birds.

Long-term trends of second generation anticoagulant rodenticides (SGARs) show widespread contamination of a bird-eating predator, the Eurasian Sparrowhawk (Accipiter nisus) in Britain

Second generation anticoagulant rodenticides (SGARs) are widely used to control rodents around the world. However, contamination by SGARs is detectable in many non-target species, particularly carnivorous mammals or birds-of-prey that hunt or scavenge on poisoned rodents. The SGAR trophic transfer pathway via rodents and their predators/scavengers appears widespread, but little is known of other pathways of SGAR contamination in non-target wildlife. This is despite the detection of SGARs in predators that do not eat rodents, such as specialist bird-eating hawks. We used a Bayesian modelling framework to examine the extent and spatio-temporal trends of SGAR contamination in the livers of 259 Eurasian Sparrowhawks, a specialist bird-eating raptor, in regions of Britain during 1995-2015. SGARs, predominantly difenacoum, were detected in 81% of birds, with highest concentrations in males and adults. SGAR concentrations in birds were lowest in Scotland and higher or increasing in other regions of Britain, which had a greater arable or urban land cover where SGARs may be widely deployed for rodent control. However, there was no overall trend for Britain, and 97% of SGAR residues in Eurasian Sparrowhawks were below 100 ng/g (wet weight), which is a potential threshold for lethal effects. The results have potential implications for the population decline of Eurasian Sparrowhawks in Britain. Fundamentally, the results indicate an extensive and persistent contamination of the avian trophic transfer pathway on a national scale, where bird-eating raptors and, by extension, their prey appear to be widely exposed to SGARs. Consequently, these findings have implications for wildlife contamination worldwide, wherever these common rodenticides are deployed, as widespread exposure of non-target species can apparently occur via multiple trophic transfer pathways involving birds as well as rodents.

Collateral damage: Anticoagulant rodenticides pose threats to California condors

Anticoagulant rodenticides (ARs) are widespread environmental contaminants that pose risks to scavenging birds because they routinely occur within their prey and can cause secondary poisoning. However, little is known about AR exposure in one of the rarest avian scavengers in the world, the California condor (Gymnogyps californianus). We assessed AR exposure in California condors and surrogate turkey vultures (Cathartes aura) to gauge potential hazard to a proposed future condor flock by determining how application rate and environmental factors influence exposure. Additionally, we examined whether ARs might be correlated with prolonged blood clotting time and potential mortality in condors. Only second-generation ARs (SGARs) were detected, and exposure was detected in all condor flocks. Liver AR residues were detected in 42% of the condors (27 of 65) and 93% of the turkey vultures (66 of 71). Although concentrations were generally low (<10 ng/g ww), 48% of the California condors and 64% of the turkey vultures exposed to ARs exceeded the 5% probability of exhibiting signs of toxicosis (>20 ng/g ww), and 10% and 13% exceeded the 20% probability of exhibiting signs toxicosis (>80 ng/g ww). There was evidence of prolonged blood clotting time in 16% of the free-flying condors. For condors, there was a relationship between the interaction of AR exposure index (legal use across regions where condors existed) and precipitation, and the probability of detecting ARs in liver. Exposure to ARs may complicate recovery efforts of condor populations within their current range and in the soon to be established northern California experimental population. Continued monitoring of AR exposure using plasma blood clotting assays and residue analysis would allow for an improved understanding of their hazard to condors, particularly if paired with recent movement data that could elucidate exposure sources on the landscape occupied by this endangered species.

Toxicokinetic analysis of the anticoagulant rodenticides warfarin & diphacinone in Egyptian fruit bats (Rousettus aegyptiacus) as a comparative sensitivity assessment for Bonin fruit bats (Pteropus pselaphon)

Anticoagulant rodenticides have been widely used to eliminate wild rodents, which as invasive species on remote islands can disturb ecosystems. Since rodenticides can cause wildlife poisoning, it is necessary to evaluate the sensitivity of local mammals and birds to the poisons to ensure the rodenticides are used effectively. The Bonin Islands are an archipelago located 1000 km southeast of the Japanese mainland and are famous for the unique ecosystems. Here the first-generation anticoagulant rodenticide diphacinone has been used against introduced black rats (Rattus rattus). The only land mammal native to the archipelago is the Bonin fruit bat (Pteropus pselaphon), but little is known regarding its sensitivity to rodenticides. In this study, the Egyptian fruit bats (Rousettus aegyptiacus) was used as a model animal for in vivo pharmacokinetics and pharmacodynamics analysis and in vitro enzyme kinetics using their hepatic microsomal fractions. The structure of vitamin K epoxide reductase (VKORC1), the target protein of the rodenticide in the Bonin fruit bat, was predicted from its genome and its binding affinity to rodenticides was evaluated. The Egyptian fruit bats excreted diphacinone slowly and showed similar sensitivity to rats. In contrast, they excreted warfarin, another first-generation rodenticide, faster than rats and recovered from the toxic effect faster. An in silico binding study also indicated that the VKORC1 of fruit bats is relatively tolerant to warfarin, but binds strongly to diphacinone. These results suggest that even chemicals with the same mode of action display different sensitivities in different species: fruit bat species are relatively resistant to warfarin, but vulnerable to diphacinone.

Anticoagulant Rodenticide Contamination of Terrestrial Birds of Prey from Western Canada: Patterns and Trends, 1988-2018

As the dominant means for control of pest rodent populations globally, anticoagulant rodenticides (ARs), particularly the second-generation compounds (SGARs), have widely contaminated nontarget organisms. We present data on hepatic residues of ARs in 741 raptorial birds found dead or brought into rehabilitation centers in British Columbia, Canada, over a 30-year period from 1988 to 2018. Exposure varied by species, by proximity to residential areas, and over time, with at least one SGAR residue detected in 74% of individuals and multiple residues in 50% of individuals. By comparison, we detected first-generation compounds in <5% of the raptors. Highest rates of exposure were in barred owls (Strix varia), 96%, and great horned owls (Bubo virginianus), 81%, species with diverse diets, including rats (Rattus norvegicus and Rattus rattus), and inhabiting suburban and intensive agricultural habitats. Barn owls (Tyto alba), mainly a vole (Microtus) eater, had a lower incidence of exposure of 65%. Putatively, bird-eating raptors also had a relatively high incidence of exposure, with 75% of Cooper's hawks (Accipiter cooperii) and 60% of sharp-shinned hawks (Accipiter striatus) exposed. Concentrations of SGARs varied greatly, for example, in barred owls, the geometric mean ∑SGAR = 0.13, ranging from <0.005 to 1.81 μg/g wet weight (n = 208). Barred owls had significantly higher ∑SGAR concentrations than all other species, driven by significantly higher bromadiolone concentrations, which was predicted by the proportion of residential land within their home ranges. Preliminary indications that risk mitigation measures implemented in 2013 are having an influence on exposure include a decrease in mean concentrations of brodifacoum and difethialone in barred and great horned owls and an increase in bromodialone around that inflection point. Environ Toxicol Chem 2022;41:1903-1917. © 2022 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Integrating terrestrial scavenging ecology into contemporary wildlife conservation and management

Scavenging plays a vital role in maintaining ecosystem health and contributing to ecological functions; however, research in this sub‐discipline of ecology is underutilized in developing and implementing wildlife conservation and management strategies. We provide an examination of the literature and recommend priorities for research where improved understanding of scavenging dynamics can facilitate the development and refinement of applied wildlife conservation and management strategies. Due to the application of scavenging research broadly within ecology, scavenging studies should be implemented for informing management decisions. In particular, a more direct link should be established between scavenging dynamics and applied management programs related to informing pharmaceutical delivery and population control through bait uptake for scavenging species, prevention of unintentional poisoning of nontarget scavenging species, the epidemiological role that scavenging species play in disease dynamics, estimating wildlife mortalities, nutrient transfer facilitated by scavenging activity, and conservation of imperiled facultative scavenging species. This commentary is intended to provide information on the paucity of data in scavenging research and present recommendations for further studies that can inform decisions in wildlife conservation and management. Additionally, we provide a framework for decision‐making when determining how to apply scavenging ecology research for management practices and policies. Due to the implications that scavenging species have on ecosystem health, and their overall global decline as a result of anthropic activities, it is imperative to advance studies in the field of scavenging ecology that can inform applied conservation and management programs.

Anticoagulant rodenticide exposure in raptors from Ontario, Canada

Anticoagulant rodenticides (ARs) are used globally to control rodent pest infestations in both urban and agricultural settings. It is well documented that non-target wildlife, including predatory birds, are at risk for secondary anticoagulant exposure and toxicosis through the prey they consume. However, there have been no large-scale studies of AR exposure in raptors in Ontario, Canada since new Health Canada legislation was implemented in 2013 in an attempt to limit exposure in non-target wildlife. Our objective was to measure levels of ARs in wild raptors in southern Ontario to assess their exposure. We collected liver samples from 133 raptors representing 17 species submitted to the Canadian Wildlife Health Cooperative (CWHC) in Ontario, Canada, between 2017 and 2019. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to quantitatively assess the level of exposure to 14 first- and second-generation ARs. Detectable levels of one or more ARs were found in 82 of 133 (62%) tested raptors, representing 12 species. The most commonly detected ARs were bromadiolone (54/133), difethialone (40/133), and brodifacoum (33/133). Of AR-positive birds, 34/82 (42%) contained residues of multiple (> 1) anticoagulant compounds. Our results indicate that AR exposure is common in raptors living in southern Ontario, Canada. Our finding that brodifacoum, difethialone, and bromadiolone were observed alone or in combination with one another in the majority of our sampled raptors indicates that legislative changes in Canada may not be protecting non-target wildlife as intended.

Short-term exposure of anticoagulant rodenticides leads to the toxin accumulation from prey (Rattus losea) to predator (Elanus caeruleus)

Rodenticides are widely used around the world since the 1950s. In Taiwan, an anti-rodent operation initiated 1977 and became a regular action annually implied by the government until 2014. This anti-rodent operation caused many animals of non-target species being exposed by rodenticides and became an environmental issue. The Black-winged Kite (Elanus caeruleus) is a small-sized diurnal raptor widely distributed in the Old World continent. Since 2000, a newly colonized population of this species occurred in Taiwan. Although the Black-winged Kites may suffer from the threats of rodenticides, the population is still growing and soon became the most abundant raptor in farmlands of Taiwan. Whether the Black-winged Kite accumulates higher anticoagulant rodenticide residues than other raptors are still unclear. In this study, liver samples of Black-winged Kites were collected from 2013 to 2016, when the detected residues of anticoagulant rodenticides increased annually. The concentration of residue rodenticide was above 0.2 ppm among 30% of the detected samples, which is the toxicity threshold concentration of other raptors. In the meanwhile, the lesser ricefield rat (Rattus losea), the most common prey of Black-winged Kites, also extended the survival period after fed on rodenticide. The longer survival days after being poisoned can enhance the predation opportunity of raptors, thus affect the accumulated rodenticides in the raptors. This study demonstrates that the Black-winged Kite has higher concentration of anticoagulant rodenticide than most other raptors, which provide the case that the raptor can quickly accumulate rodenticide residues within a short period of time.

Evaluating the effects of anticoagulant rodenticide bromadiolone in Wistar rats co-exposed to vitamin K: impact on blood-liver axis and brain oxidative status

The aim of this study was to investigate the beneficial effects of vitamin K relate to protection against detrimental effects of bromadiolone. Wistar rats (n = 30) were divided in three groups (n = 10): control group and two groups treated with bromadiolone (0.12 mg/kg) and bromadiolone + vitamin K (0.12 mg/kg + 100 mg/kg) over the period of four days. The main findings in the bromadiolone-exposed rats, such as damaged hepatocytes, high levels of globulin, total proteins and lymphocytes, and altered albumin/globulin ratio, collectively indicate an acute inflammatory process. Morphological changes in erythrocytes include microcytosis, hypochromia, hyperchromia, hemolysis, stomatocytosis, and spherocytosis. Significantly low values of RBC, Hct, and hemoglobin concentrations indicate impairments of the hematopoietic pathway causing combined anemia. The selected dose of bromadiolone caused a non-significant increase of catalase activity and a significant increase of the total protein content in brain tissue homogenates. Vitamin K supplementation reduced many of the harmful effects of bromadiolone. The cytoprotective role of vitamin K was proved to be of great importance for the preservation of structural changes on the membranes of hepatocytes and erythrocytes, in addition to the known role in the treatment of coagulopathies. The results of the study suggest valuable properties of vitamin K in the prevention and treatment of various types of anemia caused by bromadiolone toxicity. Future research is necessary to determine the adequate dose and treatment duration with vitamin K in disorders caused by the cumulative action of bromadiolone and possibly other pesticides.

Endangered Australian top predator is frequently exposed to anticoagulant rodenticides

Anticoagulant rodenticides (ARs) used to control mammalian pest populations cause secondary exposure of predatory species throughout much of the world. It is important to understand the drivers of non-target AR exposure patterns as context for assessing long-term effects and developing effective mitigation for these toxicants. In Australia, however, little is known about exposure and effects of ARs on predators. We detected AR residues in 74% of 50 opportunistically collected carcasses of the Tasmanian wedge-tailed eagle (Aquila audax fleayi), an endangered apex predator. In 22% of birds tested, or 31% of those exposed, liver concentrations of second generation ARs (SGARs) were >0.1 mg/kg ww. Eagles were exposed to flocoumafen, a toxicant only available from agricultural suppliers, at an exceptionally high rate (40% of birds tested). Liver SGAR concentrations were positively associated with the proportion of agricultural habitat and human population density in the area around where each eagle died. The high exposure rate in a species not known to regularly prey upon synanthropic rodents supports the hypothesis that apex predators are vulnerable to SGARs. Our results indicate that AR exposure constitutes a previously unrecognized threat to Tasmanian wedge-tailed eagles and highlight the importance of efforts to address non-target AR exposure in Australia.

Monitoring the hepatic residues of cis- and trans-diastereoisomers of second generation anticoagulant rodenticides reveals a different bioaccumulation of diastereoisomers in the food chain of the Réunion harrier (Circus maillardi)

The Réunion harrier is an endangered raptor and endemic species to the Réunion Island. Second generation anticoagulant rodenticides (SGARs) are widely used pesticides on the island in order to control rodent populations. The latter are responsible for the transmission of leptospirosis to humans, the damage of sugarcane crops, and the decline of endemic endangered birds. SGARs are very persistent chiral pesticides and consequent secondary exposure or poisoning of the Réunion harrier has been observed (73% of prevalence in a group of 58 harriers). Commercial formulations of SGARs are a mixture of trans- and cis-diastereoisomers. Both diastereoisomers of all SGARs have been shown to inhibit coagulation function with the same potency. On the other hand, they have been shown to have a significant difference in terms of tissue-persistence. This difference has led to residue levels in rats with a significantly lower proportion of one of the isomers compared to the bait composition. In this study, residue levels of the diastereoisomers of all SGARs were evaluated in the livers of 58 harrier carcasses. The respective concentrations and proportions of cis- and trans- diastereoisomers of all SGARs are presented. cis-Brodifacoum and trans-bromadiolone had the highest concentrations (up to 438 and 573 ng/g ww respectively), while trans-brodifacoum was less than 46 ng/g and cis-bromadiolone was barely detected. cis-Difenacoum showed the highest prevalence and the highest concentration was 82 ng/g ww, while trans-difenacoum was never detected. This study demonstrated that only cis-brodifacoum and trans-bromadiolone (and cis-difethialone, but with a low prevalence) had hepatic concentrations above a toxic threshold. The cis- and trans-diastereoisomers of SGARs had differential bioaccumulation in the food chain of the Réunion harrier compared to commercial baits. This suggests that a change of the proportions of SGARs diastereoisomers in baits could reduce the risk of secondary poisoning of predators, but maintain primary toxicity.

Intensive livestock farming as a major determinant of the exposure to anticoagulant rodenticides in raptors of the Canary Islands (Spain)

The Canary Islands (Spain) is a biodiversity hotspot, with more than 4500 registered endemic species. However, it is subject to high anthropogenic pressure that threatens its wildlife in various ways. In the context of forensic toxicological surveys, the presence of anticoagulant rodenticides (AR) has been investigated in the liver of 831 animal carcasses with georeferenced data from 2011 to May 2020. The high concentrations of toxic pesticides in carcasses and in baits found close to the corpses indicated that all the reptiles and most of the mammals tested positive for AR were intentionally poisoned, although mainly by other substances. The frequency of detection of AR in non-raptor birds (n = 343) was only 4.1%, being the Canary raven the most frequently affected species (7/97, 7.2%). On the contrary, in raptors (n = 308) the detection frequency was almost 60%, with an average of more than 2 ARs per animal. The highest concentrations were found in the common kestrel. We present for the first-time results of AR contamination in two species of raptors that are very rare in Europe, Eleonora's falcon (n = 4) and Barbary falcon (n = 13). The temporal trend of positive cases remains stable, but since the entry into force of the restriction to the concentration of the active ingredient in baits (<30 ppm), a decrease in the concentrations of these compounds in the raptors' liver has been detected. Conversely, we registered an increase in the number of ARs per animal. From the study of the geographic information system (GIS) it can be deduced that intensive livestock farms are an important determinant in the exposure of raptors to ARs. Those birds that have their territory near intensive production farms have higher levels of exposure than those of birds that live far from such facilities.

Annual abundance of common Kestrels (Falco tinnunculus) is negatively associated with second generation anticoagulant rodenticides

Rats and mice can damage food and agricultural products as well as transmit diseases, thereby requiring control of their numbers. Application of Second Generation Anticoagulant Rodenticides (SGARs) often reduces rodent numbers locally. However, predators eating rodents, including non-target species, that have consumed SGARs may be secondarily exposed and potentially lethally poisoned. Here we study whether SGARs may have contributed to the widespread population declines of a rodent-eating raptor, the Common Kestrel (Falco tinnunculus) in the UK. We show that 161 (66.8%) of the 241 Kestrels submitted for ecotoxicology tests between 1997 and 2012 had detectable levels of at least one SGAR in their livers. Adult Kestrels had significantly higher prevalence of SGARs than juveniles, suggesting accumulation of SGARs through time. The prevalence and concentrations of individual SGARs in Kestrels were significantly higher in England than in Scotland. SGAR prevalence in Kestrels were positively associated with some land cover types, primarily arable cereals and broad-leaved woodland, and negatively associated with mainly mean elevation, probably reflecting variation in SGAR usage across land cover types. By using volunteer-collected data on national Kestrel abundance 1997-2012, we show that there is a negative correlation between the Kestrel population index in a specific year and the concentration of bromadialone as well as the total SGAR concentration in the same year. Although correlative, this is the first study to provide evidence for a potential population-limiting effect of SGARs on a raptor.

Exposure of passerine birds to brodifacoum during management of Norway rats on farms

The exposure of non-target wildlife to anticoagulant compounds used for rodent control is a well-known phenomenon. Exposure can be primary when non-target species consume bait or secondary via uptake of poisoned animals by mammalian and avian predators. However, nothing is known about the exposure patterns in passerine birds that are commonly present on farms where rodent control is conducted. We used liquid chromatography coupled with tandem mass spectrometry to screen for residues of anticoagulant rodenticides (ARs) in liver tissue of passerine birds that were present during rodent control with a product containing brodifacoum (BR). The 222 birds of 13 species were bycatch of rodent snap trapping in 2011-2013 on 11 livestock farms run synchronously with baiting. During baiting, ARs were detected in about 30% of birds; 28% carried BR. In liver tissue of 54 birds that carried BR, concentrations ranged from 4 to 7809 ng/g (mean 490 ± 169 ng/g). Among common bird species with AR residues, BR was most prevalent in robins (Erithacus rubecula) (44%) and dunnocks (Prunella modularis) (41%). Mean BR concentration was highest in great tits (Parus major) (902 ± 405 ng/g). The occurrence and concentrations of BR residues were about 30% higher in birds collected close to bait stations compared to birds collected further away. The results demonstrate that several ground feeding songbird species are exposed to ARs used on farms. If BR was present in liver tissue, concentrations were variable, which may imply a combination of primary and secondary exposure of songbirds. Exposure was mostly restricted to the immediate surroundings of farms where bait was used, which might limit the transfer to the wider environment. Efforts should be made to reduce the access for birds to AR bait to prevent high exposure.

Linking landscape composition and biological factors with exposure levels of rodenticides and agrochemicals in avian apex predators from Germany

Intensification of agricultural practices has resulted in a substantial decline of Europe's farmland bird populations. Together with increasing urbanisation, chemical pollution arising from these land uses is a recognised threat to wildlife. Raptors are known to be particularly sensitive to pollutants that biomagnify and are thus frequently used sentinels for pollution in food webs. The current study focussed on anticoagulant rodenticides (ARs) but also considered selected medicinal products (MPs) and frequently used plant protection products (PPPs). We analysed livers of raptor species from agricultural and urban habitats in Germany, namely red kites (MIML; Milvus milvus), northern goshawks (ACGE; Accipiter gentilis) and Eurasian sparrowhawks (ACNI; Accipiter nisus) as well as white-tailed sea eagles (HAAL; Haliaeetus albicilla) and ospreys (PAHA; Pandion haliaetus) to account for potential aquatic exposures. Landscape composition was quantified using geographic information systems. The highest detection of ARs occurred in ACGE (81.3%; n = 48), closely followed by MIML (80.5%; n = 41), HAAL (38.3%; n = 60) and ACNI (13%; n = 23), whereas no ARs were found in PAHA (n = 13). Generalized linear models demonstrated (1) an increased probability for adults to be exposed to ARs with increasing urbanisation, and (2) that species-specific traits were responsible for the extent of exposure. For MPs, we found ibuprofen in 14.9% and fluoroquinolones in 2.3% in individuals that were found dead. Among 30 investigated PPPs, dimethoate (and its metabolite omethoate) and thiacloprid were detected in two MIML each. We assumed that the levels of dimethoate were a consequence of deliberate poisoning. AR and insecticide poisoning were considered to represent a threat to red kites and may ultimately contribute to reported decreased survival rates. Overall, our study suggests that urban raptors are at greatest risk for AR exposure and that exposures may not be limited to terrestrial food webs.

Temporal Persistence of Bromadiolone in Decomposing Bodies of Common Kestrel (Falco tinnunculus)

Bromadiolone is a second generation anticoagulant rodenticide (SGAR) used to control pest rodents worldwide. SGARs are frequently involved in secondary poisoning in rodent predators due to their persistence and toxicity. This study aims to evaluate the persistence of bromadiolone in liver at different stages of carcass decomposition in experimentally-dosed common kestrels (Falco tinnunculus) to understand the possibility of detecting bromadiolone in cases of wildlife poisoning and the potential risk of tertiary poisoning. Twelve individuals were divided into the bromadiolone-dose group (dosed with 55 mg/kg b.w) and the control group. Hepatic bromadiolone concentrations found in each stage of decomposition were: 3000, 2891, 4804, 4245, 8848, and 756 ng/g dry weight at 1–2 h (fresh carcass), 24 h (moderate decomposition), 72 h, 96 h (advanced decomposition), seven days (very advanced decomposition), and 15 days (initial skeletal reduction) after death, respectively. Liver bromadiolone concentrations in carcasses remained relatively stable over the first four days and raised on day 7 of decomposition under the specific conditions of this experiment, presenting a risk of causing tertiary poisoning. However, at the initial skeletal reduction stage, liver bromadiolone concentration declined, which should be considered to interpret toxicological analyses and for proper diagnosis. This experimental study provides for the first time some light to better understand the degradation of SGARs in carcasses in the wild.

Heavy rainfall provokes anticoagulant rodenticides' release from baited sewer systems and outdoor surfaces into receiving streams

Prevalent findings of anticoagulant rodenticide (AR) residues in liver tissue of freshwater fish recently emphasized the existence of aquatic exposure pathways. Thus, a comprehensive wastewater treatment plant and surface water monitoring campaign was conducted at two urban catchments in Germany in 2018 and 2019 to investigate potential emission sources of ARs into the aquatic environment. Over several months, the occurrence and fate of all eight ARs authorized in the European Union as well as two pharmaceutical anticoagulants was monitored in a variety of aqueous, solid, and biological environmental matrices during and after widespread sewer baiting with AR-containing bait. As a result, sewer baiting in combined sewer systems, besides outdoor rodent control at the surface, was identified as a substantial contributor of these biocidal active ingredients in the aquatic environment. In conjunction with heavy or prolonged precipitation during bait application in combined sewer systems, a direct link between sewer baiting and AR residues in wastewater treatment plant influent, effluent, and the liver of freshwater fish was established. Moreover, study results confirmed insufficient removal of anticoagulants during conventional wastewater treatment and thus indirect exposure of aquatic organisms in receiving streams via tertiary treated effluents and combined sewer overflows. Nevertheless, further research is required to determine the ecological implications and risks for aquatic organisms as well as fish-eating predators from chronic AR exposure at environmentally relevant concentrations.

Accumulation of diastereomers of anticoagulant rodenticides in wild boar from suburban areas: Implications for human consumers

We studied the prevalence of anticoagulant rodenticides (ARs) in liver and muscle tissues of wild boar captured in the urban area of Barcelona, the suburban area of Collserola Natural Park and the rural area of Santa Quiteria, next to Cabañeros National Park, in Spain. The objective was to assess the influence of both urbanisation and wild boar (Sus scrofa) trophic opportunism on the accumulation of these compounds. We have also evaluated the risk for human consumers of this game meat. Wild boars from Barcelona city showed the highest prevalence of ARs detection (60.8%), followed by the adjoining suburban area of Collserola N.P. (40%) and the rural distant area of Santa Quiteria (7.7%). Liver bioaccumulated ARs (45.2%) more frequently than muscle (11.9%). A significant proportion (13.7%) of wild boar captured in Barcelona city exceeded 200 ng/g of total ARs in liver, a threshold for adverse effects on blood clotting. For difenacoum, there was a predominance of cis isomer, while for brodifacoum and bromadiolone cis and trans isomers appeared in a similar proportion. According to the scarce available information on ARs toxicity in humans, the risk of acute poisoning from game meat consumption seems to be low. However, repeated exposure through liver consumption should be considered in further risk assessments because of the high concentration detected in some samples (up to 0.68 mg/kg).

Comparative biological properties of the four stereoisomers of difethialone, a second-generation anticoagulant rodenticide, in rats: development of a model allowing to choose the appropriate stereoisomeric ratio

The current management of rodent pest populations is based on second-generation anticoagulant rodenticides (SGAR). These molecules, of which difethialone is part, are much more efficient than the first generation. Nevertheless, this efficiency comes with a major drawback, SGARs are tissue persistent that increases the exposure of rodent predators to them. According to its chemical structure, difethialone has four stereoisomers, whose specific inhibition potency and pharmacokinetic have never been described and might be useful to design new eco-friendly rodenticides. The study aimed to investigate the ability to inhibit anticoagulant target enzyme (VKORC1) and the pharmacokinetics in rats of the four difethialone stereoisomers in rats. We show that stereoisomers are all highly efficient to inhibit VKORC1 activity, but they have distinct initial half-life with 6.0 h, 25.4 h, 69.3 h, and 82.3 h for, respectively, E4-trans, E2-cis, E1-trans, and E3-cis stereoisomer. These results open the way of the development of eco-friendly and efficient rodenticide by mixing some of these stereoisomers. Preferential incorporation of the E4-trans stereoisomer (high inhibitory VKORC1 potency, relatively shorter liver half-life) into difethialone rodenticides baits might result in a more eco-friendly product than current commercially available difethialone formulations. In addition, we put forward modelling to help design bait according to the circumstance of use (presence of non-target species, food competition, etc.) by modulating the theorical AUC and and the theorical concentration of the product at the death of the rodent pest. Thus, this modeling might allow to diminish the use of laboratory animal in assay.

Frequent detection of anticoagulant rodenticides in raptors sampled in Taiwan reflects government rodent control policy

Anticoagulant rodenticides (ARs) are known to cause extensive secondary exposure in top predators in Europe and North America, but there remains a paucity of data in Asia. In this study, we collected 221 liver samples from 21 raptor species in Taiwan between 2010 and 2018. Most birds were recovered from rescue organizations, but some free-ranging individuals were obtained from bird-strike prevention measures at airports. ARs were detected in 10 species and more than half of the total samples. Common rodent-eating Black-winged Kites (Elanus caeruleus) had the highest prevalence (89.2%) and highest average sum concentration (0.211 ± 0.219 mg/kg), which was similar between free-ranging birds at airports and injured birds from rescue organizations. Scavenging Black Kites (Milvus migrans) and snake-eating Crested Serpent-eagles (Spilornis cheela) had the second highest prevalence or sum concentration, respectively. Seven different AR compounds were detected, of which brodifacoum was the most common and had the highest average concentration, followed by flocoumafen and bromadiolone. The frequency of occurrence in the three most numerous species (Black-winged Kite, Crested Goshawk [Accipiter trivirgatus], and Collared Scops-owl [Otus lettia]) was significantly higher in autumn than summer, which is consistent with the timing of the Taiwanese government's supply of free ARs to farmers. Regional differences in the detection of individual compounds also tended to reflect differences in human population density and use patterns (in agriculture or urban-dominated environments). Clinical poisoning was confirmed in Black Kites with sum concentrations as low as 0.026 mg/kg; however, further study of interspecific differences in AR sensitivity and potential population effects are needed. In addition, continued monitoring remains important given the Taiwanese government has modified their farmland rodent control policy to gradually reduce free AR supplies since 2015.

Potential Health Risk to Humans Related to Accumulation of Brodifacoum and Bromadiolone in the Wheat Grown on Rodenticide Contaminated Soil

The aim of this study was to determine in a model experiment the potential residues of bromadiolone and brodifacoum in the wheat grown on soil treated with these rodenticides and to compare them with the respective acceptable daily intake (ADI) in order to obtain information lacking in the scientific literature. The study focused on the level of residues of chronic rodenticides Broder G, with the active ingredient brodifacoum, and DERATION G, with the active ingredient bromadiolone, in wheat (Triticum spp.). The preparations were used in the form of granular bait. In the wheat grown on the soil treated with 100 g.m−2 of the preparation BRODER G, the brodifacoum residues ranged from 0.012 to 0.0218 mg.kg−1, while the treatment of soil with 500 g.m−2 resulted in residues ranging between 0.0344 and 0.0436 mg.kg−1. When using the preparation DE-RATION G, bromadiolone residues ranged between 0.012 and 0.018 mg.kg−1 after the treatment of soil with 100 g.m−2 and between 0.030 and 0.0428 mg.kg−1 after the treatment with 500 g.m−2. We observed that the acceptable daily intake was exceeded significantly in all of the cases and the residual levels depended on the rodenticide dose. In the case of brodifacoum, the ADI was exceeded more than 700-fold at a dose of 100 g.m−2 and more than 1400-fold at a dose of 500 g.m−2 of soil. With bromadio-lone, the ADI was exceeded 150-fold at a dose of 100 g.m−2 and more than 350-fold at a dose of 500 g.m−2. This indicates the risk to consumers from such crops.

The stereoisomerism of second generation anticoagulant rodenticides: a way to improve this class of molecules to meet the requirements of society?

Second generation anticoagulant rodenticides (SGAR) are generally highly efficient for rodent management even towards warfarin-resistant rodents. Nevertheless, because of their long tissue-persistence, they are very associated with non-target exposure of wildlife and have been identified as 'Candidates for Substitution' by the European Union's competent authority. A promising way to reduce ecotoxicity issues associated to SGAR could be the improvement of SGAR based on their stereoisomery, and due to this improvement, positioning about SGAR might be reconsidered. © 2018 Society of Chemical Industry.

First evidence of anticoagulant rodenticides in fish and suspended particulate matter: spatial and temporal distribution in German freshwater aquatic systems

Anticoagulant rodenticides (ARs) have been used for decades for rodent control worldwide. Research on the exposure of the environment and accumulation of these active substances in biota has been focused on terrestrial food webs, but few data are available on the impact of ARs on aquatic systems and water organisms. To fill this gap, we analyzed liver samples of bream (Abramis brama) and co-located suspended particulate matter (SPM) from the German Environmental Specimen Bank (ESB). An appropriate method was developed for the determination of eight different ARs, including first- and second-generation ARs, in fish liver and SPM. Applying this method to bream liver samples from 17 and 18 sampling locations of the years 2011 and 2015, respectively, five ARs were found at levels above limits of quantifications (LOQs, 0.2 to 2 μg kg^-1). For 2015, brodifacoum was detected in 88% of the samples with a maximum concentration of 12.5 μg kg^-1. Moreover, difenacoum, bromadiolone, difethialone, and flocoumafen were detected in some samples above LOQ. In contrast, no first generation AR was detected in the ESB samples. In SPM, only bromadiolone could be detected in 56% of the samples at levels up to 9.24 μg kg^-1. A temporal trend analysis of bream liver from two sampling locations over a period of up to 23 years revealed a significant trend for brodifacoum at one of the sampling locations.

Urbanization and cattle density are determinants in the exposure to anticoagulant rodenticides of non-target wildlife

The persistence and toxicity of second generation anticoagulant rodenticides (SGARs) in animal tissues make these compounds dangerous by biomagnification in predatory species. Here we studied the levels of SGARs in non-target species of wildlife and the environmental factors that influence such exposure. Liver samples of terrestrial vertebrates (n = 244) found dead between 2007 and 2016 in the region of Aragón (NE Spain) were analysed. The presence of SGARs was statistically analysed with binary or ordinal logistic models to study the effect of habitat characteristics including human population density, percentage of urban surface, livestock densities and surface of different types of crops. SGARs residues were detected in 83 (34%) of the animals and levels >200 ng/g were found in common raven (67%), red fox (50%), red kite (38%), Eurasian eagle-owl (25%), stone marten (23%), Eurasian buzzard (17%), northern marsh harrier (17%), and Eurasian badger (14%). The spatial analysis revealed that the presence of SGARs residues in wildlife was more associated with the use of these products as biocides in urban areas and cattle farms rather than as plant protection products in agricultural fields. This information permits to identify potential habitats where SGARs may pose a risk for predatory birds and mammals.

A review: poisoning by anticoagulant rodenticides in non-target animals globally

Worldwide use of anticoagulant rodenticides (ARs) for rodents control has frequently led to secondary poisoning of non-target animals, especially raptors. In spite of the occurrence of many incidents of primary or secondary AR-exposure and poisoning of non-target animals, these incidents have been reported only for individual countries, and there has been no comprehensive worldwide study or review. Furthermore, the AR exposure pathway in raptors has not yet been clearly identified. The aim of this review is therefore to comprehensively analyze the global incidence of primary and secondary AR-exposure in non-target animals, and to explore the exposure pathways. We reviewed the published literature, which reported AR residues in the non-target animals between 1998 and 2015, indicated that various raptor species had over 60% AR- detection rate and have a risk of AR poisoning. According to several papers studied on diets of raptor species, although rodents are the most common diets of raptors, some raptor species prey mainly on non-rodents. Therefore, preying on targeted rodents does not necessarily explain all causes of secondary AR-exposure of raptors. Since AR residue-detection was also reported in non-target mammals, birds, reptiles and invertebrates, which are the dominant prey of some raptors, AR residues in these animals, as well as in target rodents, could be the exposure source of ARs to raptors.

Anticoagulant rodenticide exposure in an Australian predatory bird increases with proximity to developed habitat

Anticoagulant rodenticides (ARs) are commonly used worldwide to control commensal rodents. Second generation anticoagulant rodenticides (SGARs) are highly persistent and have the potential to cause secondary poisoning in wildlife. To date no comprehensive assessment has been conducted on AR residues in Australian wildlife. My aim was to measure AR exposure in a common widespread owl species, the Southern Boobook (Ninox boobook) using boobooks found dead or moribund in order to assess the spatial distribution of this potential threat. A high percentage of boobooks were exposed (72.6%) and many showed potentially dangerous levels of AR residue (>0.1 mg/kg) in liver tissue (50.7%). Multiple rodenticides were detected in the livers of 38.4% of boobooks tested. Total liver concentration of ARs correlated positively with the proportions of developed areas around points where dead boobooks were recovered and negatively with proportions of agricultural and native land covers. Total AR concentration in livers correlated more closely with land use type at the spatial scale of a boobook's home range than at smaller or larger spatial scales. Two rodenticides not used by the public (difethialone and flocoumafen) were detected in boobooks indicating that professional use of ARs contributed to secondary exposure. Multiple ARs were also detected in recent fledglings, indicating probable exposure prior to fledging. Taken together, these results suggest that AR exposure poses a serious threat to native predators in Australia, particularly in species using urban and peri-urban areas and species with large home ranges.

Investigating spatial patterns of mercury and rodenticide residues in raptors collected near the Charlotte, NC, USA, metropolitan area

Raptor population growth is dynamic and trends vary across species and by location in the United States. For those species that are declining, it is important to identify potential causes including chemical contaminants. Sampling wild raptors is problematic due to their small population sizes and role as a top predator. Therefore, we obtained liver samples (n = 56) from carcasses of several raptor species, including common species like red-tailed hawks, red-shouldered hawks, barred owls, great horned owls, and osprey that arrived dead or were euthanized from a non-profit rehabilitation center in Charlotte, North Carolina. Raptors were found or collected in South Carolina, North Carolina, and Virginia, but most samples were located near the metropolitan region of Charlotte, NC. We analyzed livers for total mercury residue (mg/kg, dry weight) and five anti-coagulant rodenticides (μg/kg wet weight). Mercury was analyzed using a direct mercury analyzer approach and rodenticides were quantified by LC-MS. Mercury residues were high in piscivorous birds (15.09 mg/kg for osprey and 6.93 mg/kg for great blue herons, dry weight) and relatively high in red-shouldered hawks and one eastern screech owl tested. Six of our samples exceeded a health threshold of 1 mg/kg (wet weight) including three osprey and one each of great blue heron, red-shouldered hawk, and eastern screech owl. Brodifacoum was the only rodenticide consistently detected in our samples. Brodifacoum detections exceeded 75% in barred owls, great horned owls, and red-shouldered hawks. Sixty-nine percent of owl samples were within (or exceeded) a threshold of brodifacoum residue associated with a 10-20% risk of acute toxicity. Correlations between residues and human population density were not significant for either mercury or brodifacoum. Our data suggest that mercury residues for most raptors were not of significant concern with the exception of osprey and possibly red-shouldered hawks. Rodenticide exposures associated with a risk of acute toxicity appear to be common and warrant further investigation.

Start-up financing of professional pest control in pig farming in North Rhine-Westphalia in Germany

Background

Due to the risk of spreading epizootic diseases through rodents, pest control is mandatory in pig farming in European countries. However, there is limited research focused on rodent control practices, usage of anticoagulant rodenticides, and the acceptance of Pest Control Operators (PCOs) in pig farming in Germany. Therefore, the present study aims to investigate current control practices in pig holdings and to analyze the potential of a financial support on the implementation of professional pest control.

Results

Data were collected from monitoring records of PCOs and personal interviews with farmers and PCOs. 33 of 47 farmers, who were offered the possibility to outsource rodent control to PCOs supported by financial contribution of the North Rhine-Westphalian Animal Disease Fund (TSK) for a period of 2 years, joined the project.Despite the widespread opinion that the professional would not be beneficial - the authors figured out that farmers could financially benefit in time saved and by improved rodent control measures from the work of the PCOs. Costs of pest control measures per operation on average did not differ significantly between costs incurred by employment of PCOs (1.310 € per year) and calculated costs that arise by farmers themselves (1.217 € per year).All PCOs used Difenacoum and Brodifacoum against pest infestations. In doing so, the infestation with rodents was reduced and most of the participating farmers assessed the project as successful and employ the PCOs permanently. However, mapping the farm locations to resistance areas of the Rodenticide Resistance Action Committee (RRAC) shows that Brodifacoum was frequently used in areas which are marked as areas that are at low risk or rather have no risk for resistance. The environmental risks, however, are increased in these areas.

Conclusion

The instrument of temporal start-up financing professional pest control allows ensuring the continuous engagement of PCOs after the project period. This could possibly lead to long-term effects on the individual farm hygiene and on disease prevention. Nevertheless, important research questions with regard to the application of anticoagulant rodenticides of farmers and PCOs in livestock farming and with regard to risk mitigation measures were generated, meriting further investigation.

Elevated difenacoum metabolism is involved in the difenacoum-resistant phenotype observed in Berkshire rats homozygous for the L120Q mutation in the vitamin K epoxide reductase complex subunit 1 (Vkorc1) gene

BACKGROUND

Soon after difenacoum began to be used, resistance to this rodenticide was detected in rats in northeast Hampshire and northwest Berkshire in England. Resistance to difenacoum has been reported to be stronger in rats from Berkshire than in rats from Hampshire. Surprisingly, after the discovery of the vitamin K epoxide reductase complex subunit 1 (Vkorc1) gene, rats from Berkshire and Hampshire were all shown to be homozygous for the L120Q mutation in Vkorc1.

RESULTS

This study aimed to evaluate the resistance of Berkshire rats to confirm their extreme resistance and determine mechanisms supporting this resistance. For this purpose, we created a quasicongenic rat F7 strain by using a Berkshire rat as a donor to introduce the L120Q mutation in Vkorc1 into the genetic background of an anticoagulant-susceptible recipient strain. The use of F7 rats enabled demonstration of (i) the level of resistance to difenacoum conferred by the L120Q mutation, (ii) co-dominance of the L120 and Q120 alleles, (iii) the extreme resistance of Berkshire rats compared with Q120/Q120 rats as a consequence of additional resistance mechanisms, and (iv) the involvement of cytochrome P 450 (CYP450) enzymes in this extreme resistance.

CONCLUSION

This study demonstrated that elevated CYP450 oxidative metabolism leading to accelerated difenacoum detoxification is involved in the Berkshire phenotype. © 2017 Society of Chemical Industry.

Long-term increase in secondary exposure to anticoagulant rodenticides in European polecats Mustela putorius in Great Britain

As a result of legal protection and population recovery, European polecats (Mustela putorius) in Great Britain are expanding into areas associated with greater usage of second-generation anticoagulant rodenticides (SGARs). We analysed polecat livers collected from road casualties from 2013 to 2016 for residues of five SGARs. We related variation in residues to polecat traits and potential exposure pathways, by analysing stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) in their whiskers. 54 of 68 (79%) polecats had detectable residues of at least one SGAR. Bromadiolone (71%) was the most frequently detected compound, followed by difenacoum (53%) and brodifacoum (35%). Applying historical limits of detection to allow comparison between these new data and previous assessments, we show that in the 25 years from 1992 to 2016 inclusive, the rate of detection of SGARs in polecats in Britain has increased by a factor of 1.7. The probability of SGAR detection was positively related to increasing values of δ¹⁵N, suggesting that polecats feeding at a higher trophic level were more likely to be exposed. Total concentrations of SGARs in polecats with detectable residues were higher in polecats collected in arable compared to pastoral habitats, and in the west compared to the east of Britain. The number of compounds detected and total concentrations of SGARs increased with polecat age. There was no evidence of regional or seasonal variation in the probability of detecting SGARs, suggesting that the current risk of exposure to SGARs does not vary seasonally and has increased (from that in the 1990s) throughout the polecat's range. We recommend quantification of current practices in rodenticide usage, particularly in the light of recent regulatory changes, to enable assessment and mitigation of the risks of secondary exposure to rodenticides in non-target wildlife.

Multi-residue determination of anticoagulant rodenticides in vertebrate wildlife and domestic animals using Ultra (High) Performance Liquid Chromatography Tandem Mass Spectrometry

Anticoagulant rodenticide (AR) products are used globally to control rodent pests in domestic, urban, agricultural and industrial environments. However, there is a substantial volume of evidence that non-target vertebrate wildlife i.e. predators and scavengers in particular and other animals, are vulnerable to contamination via direct or indirect routes of exposure. The determination of multiple AR residues in liver tissue samples that can range from remnants of a small bird of prey liver to an intact liver from a large mammal is complicated as residue levels encountered can vary considerably too. So, the utilisation of ultra-sensitive systems has to be carefully considered in order to allow routine application of the method to all sample compositions presented for analysis. The UHPLC–MSMS method described now:

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permits quantitative analysis of ultra-low levels of multiple-residues (0.0025–1 mg kg⁻¹) in a single experiment.

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uses the same U(H)PLC column for the determination of AR and multiple-pesticide residue in similar specimens.

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allows higher sample throughput due to shaking rather than tumbling of samples during the extraction procedure.

Cis-bromadiolone diastereoisomer is not involved in bromadiolone Red Kite (Milvus milvus) poisoning

Anticoagulant rodenticides (ARs) are widely used pesticides to control rodent populations. Bromadiolone, a second generation anticoagulant rodenticide (SGARs), is authorized in France to control the population of water voles (Arvicola scherman). The persistence of SGARs in rodents is responsible for secondary exposure or poisoning of predators and scavengers, and is of ecological concern for the conservation of endangered species. Commercial formulations are a mixture of two diastereoisomers of bromadiolone: 70-90% is trans-bromadiolone and 10-30% is cis-bromadiolone. Both diastereoisomers have been shown to inhibit coagulation function with the same potency. On the other hand, cis-bromadiolone has been shown to be less tissue-persistent than trans-bromadiolone in rats. This difference led to residue levels in rats with substantially weakened proportion in cis-bromadiolone compared to the composition of baits. In this study, a multi-residue LC-MS/MS method for the quantification of the diastereoisomers of SGARs was used to investigate their proportions in field samples of predators. In 2011, 28 red kites (Milvus milvus) were found dead within a few months of bromadiolone application in grassland to control water vole outbreaks. In this study, we report the concentrations of the two diastereoisomers of bromadiolone measured in the livers of thirteen red kites. Exposure to bromadiolone was apparent in all the kites with hepatic concentrations of trans-bromadiolone ranging from 390 to 870ng/g (89 to 99% of summed SGARs). However, cis-bromadiolone was not detected in 5 of 13 red kites and was present at very low concentrations (below 2.2ng/g) in 8 of 13 kites, demonstrating that cis-bromadiolone is not involved in this red kite poisoning event. 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 rodent outbreaks.

Adaptative evolution of the Vkorc1 gene in Mus musculus domesticus is influenced by the selective pressure of anticoagulant rodenticides

Anticoagulant rodenticides are commonly used to control rodent pests worldwide. They specifically inhibit the vitamin K epoxide reductase (VKORC1), which is an enzyme encoded by the Vkorc1 gene, involved in the recycling of vitamin K. Therefore, they prevent blood clotting. Numerous mutations of Vkorc1 gene were reported in rodents, and some are involved in the resistant to rodenticides phenotype. Two hundred and sixty‐six mice tails were received from 65 different locations in France. Coding sequences of Vkorc1 gene were sequenced in order to detect mutations. Consequences of the observed mutations were evaluated by the use of recombinant VKORC1. More than 70% of mice presented Vkorc1 mutations. Among these mice, 80% were homozygous. Contrary to brown rats for which only one predominant Vkorc1 genotype was found in France, nine missense single mutations and four double mutations were observed in house mice. The single mutations lead to resistance to first‐generation antivitamin K (AVKs) only and are certainly associated with the use of these first‐generation molecules by nonprofessionals for the control of mice populations. The double mutations, probably obtained by genetic recombination, lead to in vitro resistance to all AVKs. They must be regarded as an adaptive evolution to the current use of second‐generation AVKs. The intensive use of first‐generation anticoagulants probably allowed the selection of a high diversity of mutations, which makes possible the genetic recombination and consequently provokes the emergence of the more resistant mutated Vkorc1 described to date.

A negative association between bromadiolone exposure and nestling body condition in common kestrels: management implications for vole outbreaks

BACKGROUND

Vole outbreaks have been extensively described, along with their impacts on humans, particularly in agricultural areas. The use of rodenticides is a common legal practice to minimise crop damage induced by high vole density for biocidal use. However, rodenticides can have negative direct and indirect impacts on non-target species that feed on voles. We studied whether the use of a second-generation anticoagulant rodenticide (SGAR), bromadiolone, can be detected in the blood of fledglings of wild common kestrels Falco tinnunculus in two areas of central Spain, exploring its possible indirect effects.

RESULTS

We found that 16.9% of fledglings had a detectable concentration of bromadiolone in their blood, with an average concentration of 0.248 ± 0.023 ng mL^-1 . Fledglings with bromadiolone in their blood, regardless of the concentration, had 6.7% lower body mass than those without detectable bromadiolone.

CONCLUSION

The use of bromadiolone was detectable in the blood of alive non-target species. Detected bromadiolone in blood may reduce the body condition of nestlings, potentially reducing their fitness. The source of bromadiolone found in nestlings needs to be determined in future studies to derive accurate management advice. However, we urge the discontinuation of official SGAR distribution to farmers and their use in agrarian lands to minimise damage of voles on crops, particularly where common kestrels breed, and encourage the use of alternative effective practices. © 2016 Society of Chemical Industry.

Use of anticoagulant rodenticides by pest management professionals in Massachusetts, USA

Secondary exposure to chemical rodenticides, specifically second-generation anticoagulant rodenticides (SGARs), poses a threat to non-target wildlife including birds of prey. Federal regulations in the United States currently limit homeowner access to SGARs as a way of minimizing this threat. With legal access to SGARs, pest management professionals (PMPs) represent a potential linkage to non-target exposure. There is limited research focused on rodent control practices, chemical rodenticide preferences, level of concern and awareness, or opinions on rodenticide regulations as they relate to PMPs. An online survey was sent to PMP companies across Massachusetts, USA, between October and November 2015. Thirty-five responses were obtained, a 20 % response rate. The preferred rodent control method among responding PMP companies was chemical rodenticides, specifically the SGAR bromadiolone. Respondents varied in their level of concern regarding the impact of chemical rodenticides on non-target species and showed a low level of awareness regarding SGAR potency and half-life. All responding companies reported using integrated pest management (IPM) strategies, with nearly all utilizing chemical rodenticides at some point. Enhanced education focused on SGAR potency, bioaccumulation potential, exposure routes, and negative impacts on non-target wildlife may improve efforts made by PMPs to minimize risk to wildlife and decrease dependence on chemical rodenticide use. Future studies evaluating use of anticoagulant rodenticide (ARs) by PMPs and the association with AR residues found in non-target wildlife is necessary to determine if current EPA regulations need to be modified to effectively reduce the risk of SGARs to non-target wildlife.

Management of Rodent Populations by Anticoagulant Rodenticides: Toward Third-Generation Anticoagulant Rodenticides

Second-generation anticoagulant rodenticides (SGARs) have been used since the 1980s for pest management. They are highly efficient even in warfarin-resistant rodents. Nevertheless, because of their tissue persistence, nontarget poisoning by SGARs is commonly described in wildlife. Due to this major problem, a new generation of anticoagulants must be developed to limit this risk. This study proposes a method of developing a new generation of anticoagulant rodenticides by revisiting the old SGARs based on the concept of stereochemistry. Each current SGAR is a mixture of diastereomers. Diastereomers of each compound were purified, and their biologic properties were compared by determining their ability to inhibit vitamin K epoxide reductase (VKOR) activity involved in the activation of vitamin K-dependent clotting factors and their toxicokinetic properties. Systematically, for each SGAR, both diastereomers are as effective in inhibiting VKOR activity. However, their toxicokinetic properties are very different, with one of the two diastereomers always more rapidly cleared than the other one. For all SGARs except flocoumafen, the less persistent diastereomer is always the less predominant isomer present in the current mixture. Therefore, the development of baits containing only the less persistent diastereomer would avoid the ecotoxicological risk associated with their use without decreasing their efficacy.