First evidence of widespread anticoagulant rodenticide exposure of the Eurasian otter (Lutra lutra) in Germany

Anticoagulant rodenticide exposure in endangered American badgers (Taxidea taxus) and fishers (Pekania pennanti) from British Columbia, Canada, 1998 to 2018

Anticoagulant rodenticide (AR) concentrations in livers of 69 samples of two mustelid species, collected 1998 to 2018 from locations in British Columbia, Canada are presented. The American badger Taxidea taxus is endangered in Canada, and fisher Pekania pennanti populations are at-risk. Using a high performance liquid chromatography method, we measured liver concentrations of the following second generation ARs (SGARs): brodifacoum, bromadiolone, difethialone and the first generation (FGAR) compounds: warfarin, diphacinone and chlorophacinone in 59 badgers and 10 fishers. Of the 59 badgers analyzed, 69 % (n = 41) contained residues of one or more ARs. The mean total AR exposure was 201 ng/g (wet weight) (range: 4.0-214 ng/g) with an average of three compounds detected (range 1-6) per individual. Male badgers had twice the concentration levels as females (182 ± 300 ng/g versus 93 ± 170 ng/g). The SGARs bromadiolone (n = 33) and brodifacoum (n = 21) were the most common ARs detected. Four badgers had AR levels >1000 ng/g and eight had >500 ng/g in their livers. The highest average concentrations were from badgers collected in the East Kootenay region (FGAR: 165 ± 210 ng/g, SGAR: 295 ± 517 ng/g). Six female badgers were lactating and all were exposed to rodenticides. We found no spatial relationship between development and exposure levels in badgers. In Fishers, one juvenile female was exposed to warfarin (5 ng/g) and bromadiolone (528 ng/g), and an adult female tested positive for brodifacoum (13 ng/g). Regardless of the lower incidences of exposure, finding such high levels of SGARs was surprising given that fishers are a shy forest carnivore species.

Exploring anticoagulant rodenticide exposure and effects in eagle owl (Bubo bubo) nestlings from a Mediterranean semiarid region

Anticoagulant rodenticides (ARs) are widely used for pest control, resulting in their pervasive presence in the environment and posing significant toxicological risks to a range of predatory and scavenging species. Our study mainly aimed to evaluate AR exposure and effects in nestlings of eagle owl (Bubo bubo) from the Region of Murcia (southeastern Spain). We analysed ARs in blood samples (n = 106) using high-performance liquid chromatography-triple quadrupole (HPLC-TQ), assessed the influence of potential anthropogenic (presence of livestock farms, landfills and human population density) and environmental (land uses and proximity to watercourses) variables, and measured prothrombin time (PT) and plasma biochemical parameters as biomarkers of effects. Our results showed the presence of AR residues in 91.5% of the nestlings, with 70.8% exhibiting multiple ARs (up to six compounds in a single individual). Second-generation ARs (SGARs) were the most prevalent compounds. The analysis of biochemical parameters indicated that the sampled individuals were in good physiological condition. Although PT was positively correlated with total AR concentration (ΣARs), the relationship was not significant (Rho = 0.04; p = 0.49). Regarding environmental factors, higher ΣARs were associated with the most urbanised study site and the presence of landfills, likely due to the increased availability of rodent prey. The prevalence of two SGARs (brodifacoum and difenacoum) was linked to closer proximity to riverbeds, suggesting a contamination pathway associated with inland aquatic ecosystems, where these AR compounds may concentrate due to water scarcity. This study underscores the widespread exposure of eagle owls to ARs and highlights the importance of effective monitoring and management of these pollutants to protect conservation-concern wildlife in Mediterranean semiarid regions.

First evidence of the suitability of hair for assessing wildlife exposure to anticoagulant rodenticides (ARs)

Anticoagulant rodenticides (ARs) are potent pesticides acting as vitamin K epoxide reductase inhibitors causing haemorrhaging or external bleeding from orifices and/or skin lesions in intoxicated rodents. However, their non-selective mode of action makes them particularly harmful for non-target wildlife, which may be exposed to ARs via ingestion of AR-containing baits (primary exposure), feeding on AR-intoxicated rodents and carrions (secondary exposure), consuming AR-contaminated necrophagous species (tertiary exposure), and exposure to surface waters receiving baited sewer systems and ARs from outdoor-placed traps after heavy rain events. In the present study, we assessed the suitability of hairs as a non-invasive matrix for monitoring the possible exposure of mammals to ARs with a focus on the first-generation anticoagulant rodenticides (FGARs) warfarin, coumatetralyl, and chlorophacinone and the second-generation anticoagulant rodenticides (SGARs) brodifacoum, bromadiolone, difenacoum, flocoumafen, and difethialone. The Red fox (n = 24) was selected as the species representing the potentially exposed non-target wildlife in a littoral area of Northern Italy along the Adriatic coast (Cavallino-Treporti municipality). Half (n = 12) of the analysed hair samples were positive for at least one of the targeted ARs, with a higher prevalence of SGARs (n = 11; 46%) compared to FGARs (n = 1; 4%). The most frequently quantified ARs were brodifacoum (25%), difethialone (13%), and flocoumafen (13%), with concentrations ranging from 0.08 ng g-1 (difethialone) to 0.96 ng g-1 (brodifacoum). These data documented that a relevant part of the Red foxes living in the study area were exposed to ARs and, most importantly, provided the first evidence that hair residues can be used as a non-invasive matrix for assessing the possible exposure of mammals to ARs.

Trends in extraction techniques for the determination of organic micropollutants in liver tissues of vertebrates

Determining organic micropollutants in liver samples of apex species is of foremost importance for biomonitoring studies, as it can provide evidence of environmental pollution and exposure of living organisms to chemicals. This review aims to provide a 4-year overview and summarize the trends in the extraction methodologies to determine both polar and non-polar organic micropollutants in liver samples from organisms of higher trophic levels. The dominant extraction techniques including ultrasound-assisted extraction (UAE), pressurized liquid extraction (PLE), Soxhlet, and QuEChERS, as well as additional steps and/or modifications applied in the reviewed studies, are presented and critically discussed. The latest trends in these methods as well as a comparison between them considering elapsed time, robustness, cost, and environmental fingerprint are also provided.

Exposure to anticoagulant rodenticides in steppe polecat (Mustela eversmanii) and European polecat (Mustela putorius) in central Europe

Poisoning caused by coumarin-type anticoagulant rodenticides (ARs) stands as the predominant method for controlling rodents globally. ARs, through secondary poisoning, pose a significant threat to predators due to their lethal and sublethal effects. We examined the concentration of accumulated ARs in liver samples of mostly road-killed steppe polecats (Mustela eversmanii) and European polecats (M. putorius) collected throughout Hungary between 2005 and 2021. The steppe polecat samples were found mainly from Eastern Hungary, while European polecats from Western Hungary. We measured the concentration of six residues by HPLC-FLD. Our analysis revealed the presence of one first-generation and four second-generation ARs in 53% of the steppe polecat (36) and 39% of the European polecat (26) samples. In 17 samples we detected the presence of at least two AR compounds. Although we did not find significant variance in AR accumulation between the two species, steppe polecats displayed greater prevalence and maximum concentration of ARs, whereas European polecat samples exhibited a more diverse accumulation of these compounds. Brodifacoum and bromadiolone were the most prevalent ARs; the highest concentrations were 0.57 mg/kg and 0.33 mg/kg, respectively. The accumulation of ARs was positively correlated with human population density and negatively correlated with the extent of the more natural habitats in both species. To the best of our knowledge, this is the first study to demonstrate anticoagulant rodenticide exposure in steppe polecats globally, and for European polecats in Central European region. Although the extent of AR accumulation in European polecat in Hungary appears comparatively lower than in many other European countries, the issue of secondary poisoning remains a serious problem as these ARs intrude into food webs. Reduced and more prudent usage of pesticides would provide several benefits for wildlife, included humans. However, we advocate a prioritization of ecosystem services through the complete prohibition of the toxicants.

A strategy to improve rodent control while reducing rodenticide release into the environment

In addition to having a negative impact on the health of people and domestic animals, rodents often cause enormous damage to the environment by disrupting natural biodiversity. The negative impacts of rodents in urban and rural areas have required intensive use of rodentcides in spite of the proven risk of secondary poisoning of non-target predators and scavengers. Continuous and intensive use of rodenticides has led to environmental pollution through their retention in the environment. Commensal rodents are predominantly managed with anticoagulant rodenticides, which are very persistent in the environment and move up the food chain and accumulate in the bodies of predators and scavengers. Generally, the use of anticoagulant rodenticides continues, and there is a need to take appropriate measures to reduce their harmful impact. The efficacy of second generation anticoagulants (bromadiolone, difenacoum and brodifacoum), combined either mutually or with chlorophacinone at reduced doses (0.001 % and 0.0008 %), in controlling brown rats (Rattus norvegicus) was tested in a four-day no-choice feeding test. Combinations of second generation anticoagulants were more effective than the combination of chlorophacinone and second generation anticoagulants. The results indicate that combinations of different anticoagulants at multifold lower doses than the standard may provide a successful tool for brown rat control and a more environment-friendly method of rodent control and protection of non-target animals.

Toxicology of chemical biocides: Anticoagulant rodenticides - Beyond hemostasis disturbance

The use of anticoagulant rodenticides (ARs) is one of the most commonly employed management methods for pest rodents. ARs compete with vitamin K (VK) required for the synthesis of blood clotting factors in the liver, resulting in inhibition of blood coagulation and often animal death due to hemorrhage. Besides rodents (target species), ARs may affect non-target animal species and humans. Out of hemostasis disturbance, the effects of ARs may be related to the inhibition of proteins that require VK for their synthesis but are not involved in the coagulation process, to their direct cytotoxicity, and their pro-oxidant/proinflammatory activity. A survey of the cellular and molecular mechanisms of these sublethal/asymptomatic AR effects is given in this review. Data from field, clinical, and experimental studies are presented. Knowledge of these mechanisms might improve hazard characterization and identification of potential ecotoxicological risks associated with ARs, contributing to a safer use of these chemicals.

Farmers' Attitudes in Connection with the Potential for Rodent Prevention in Livestock Farming in a Municipality in North Rhine-Westphalia, Germany

Rodents in livestock farming constitute a threat to the one health approach. In the present observational case study, livestock farmers worked together with a pest controller within a pilot project. The aim of the study was to assess determinants associated with rodent-prevention potential. The study started in March 2019 on 24 livestock farms in a municipality in North Rhine-Westphalia/Germany. At the beginning of the project a survey on the determinants expected to be related to prevention potential was conducted. To determine the potential for rodent prevention, an expert person, who was not involved in the project before, assessed the on-site conditions of the farms after 1.5 years of project duration in 2020. The potential for rodent prevention was good for about half of the farms. There were significant differences in the willingness to make changes at the project's start between farms with a high and a low potential for rodent prevention after 1.5 years. There is a general need for action to provide farmers with more practical information on rodent control. This is aggravated by the insufficient advisory services offered to farmers. This study confirms the importance of implementing preventive measures in the control of rodents to ensure that anticoagulant rodenticides are handled responsibly to reduce the impact on non-target species.