Anticoagulant Rodenticide Exposure Research Articles

Differential exposure to second-generation anticoagulant rodenticides in raptors from continental and insular regions of the Iberian Peninsula

The global impact of anticoagulant rodenticides (ARs) on non-target species is well-recognized. Birds of prey, as apex predators, are highly vulnerable to AR exposure and are widely used as biomonitors for priority pollutants in Europe. This study investigates differential SGAR exposure in raptors from insular versus continental regions, hypothesizing greater exposure in insular areas due to ecological factors like reduced prey diversity, intensive rodenticide use, and resistant rodent populations. We analyzed the livers of 190 common kestrels (Falco tinnunculus) and 104 common buzzards (Buteo buteo) across the Iberian Peninsula and its archipelagos using LC-MS/MS to assess their role as AR sentinels and the differences between insular and continental areas. Results revealed a high prevalence (>80%) of second-generation anticoagulant rodenticides (SGARs), with brodifacoum and bromadiolone, being the most frequent. Multiple SGAR detections were also common (≈50%). A binomial logistic regression showed that species and region significantly influence the likelihood of SGAR exposure. Kestrels had a greater probability of exceeding 100 ng/g wet weight (ww) compared to buzzards. Raptors from insular territories were ten times more likely to have higher SGAR concentrations than those from continental areas. However, the legal restriction on SGAR bait concentrations that came into effect in 2018 did not significantly impact exposure levels. This study highlights the need for targeted conservation efforts to mitigate AR exposure risk in vulnerable island ecosystems.

Comparing anticoagulant rodenticide exposure in barn owl (Tyto alba) and common kestrel (Falco tinnunculus): A biomonitoring study in an agricultural region of southeastern Spain

Second-generation anticoagulant rodenticides (SGARs) are commonly used for rodent control, affecting various non-target wildlife species. Here, blood samples from common kestrels (Falco tinnunculus, n = 70 chicks) and barn owls (Tyto alba, n = 54 chicks and 12 adults) from Southeastern Spain were analysed using HPLC-TQ. SGAR prevalence was 68.6% in kestrel chicks, 50% in barn owl chicks and 100% in adult barn owls, with multiple SGARs in both species. Prothrombin time analysis in barn owls revealed a positive correlation with blood ΣSGARs, suggesting a potential adverse effect on coagulation. Analysis of variables potentially influencing SGAR prevalence indicated that, for kestrels, it was only related to the extent of artificial surface, showing no differences across study sites. In owlets, the highest prevalence occurred in the most urbanized study site, with human population density being a key factor. This study highlights species-specific differences in SGAR exposure, likely influenced by ecological traits. Barn owls probably encounter contaminated prey near anthropized areas, with widespread SGAR use and higher presence of target rodents. Conversely, kestrels, hunting a variety of prey often near human settlements, face consistently elevated exposure from multiple sources. Understanding these variations is crucial for effective conservation and minimizing SGAR impact on non-target wildlife.

Turkey Vultures (Cathartes aura) from Southern California are Exposed to Anticoagulant Rodenticides Despite Recent Bans

ABSTRACT Secondary poisoning with anticoagulant rodenticides (ARs) has been identified as an important threat for raptor conservation worldwide. In 2019, the California State Legislature passed Assembly Bill 1788 (made effective in 2020), which prohibits or limits the use of second-generation anticoagulant rodenticides (SGARs) in the state, as a follow-up to the California Department of Pesticide Regulation’s ban on SGARS implemented in 2014. Currently, the adherence to these recent restrictions on ARs in southern California is unknown. To assess whether these bans prevented exposure of raptors and other wildlife to ARs, we investigated (1) the prevalence of exposure to eight different ARs in the blood of Turkey Vultures (Cathartes aura) before and after the 2019 ban, and (2) the distribution of resighted (encountered) wing-tagged Turkey Vultures included in this study to assess where exposure might occur. Of 27 Turkey Vultures tested for eight ARs, one out of 11 sampled in 2017 had detectable (trace) but not quantifiable levels of difethialone, and two out of 16 (12.5%) sampled in 2021 had detectable levels of diphacinone (one had 8 ppb; another indicated as positive without quantification). Overall, the prevalence of exposure to ARs was 11.1% (3 of 27), 7.4% for diphacinone and 3.7% for difethialone. Based on 93 resightings of 20 of the wing-tagged Turkey Vultures, all but one remained within the areas of Los Angeles, San Bernardino, Orange, Riverside, and San Diego Counties of southern California. Our study suggests that the exposure risk of Turkey Vultures to ARs persisted despite recent restrictions. Our small sample size and reliance on blood in live vultures rather than liver tissue in dead ones may be underestimating true ARs exposure in our study population. We propose a continued and integrated monitoring approach that includes measurements of ARs in both free-ranging (blood samples) and deceased (liver samples) Turkey Vultures for effective large-scale monitoring. This approach will assess compliance with current and future bans and regulations regarding the use of these poisons in California.

Widespread exposure to anticoagulant rodenticides among common urban mesopredators in Chicago

Anticoagulant rodenticides (ARs) are currently the most common method to control rats in cities, but these compounds also cause morbidity and mortality in non-target wildlife. Little attention has been focused on AR exposure among mesopredators despite their ecological role as scavengers and prey for larger carnivores, thus serving as an important bridge in the biomagnification of rodenticides in food webs. In this study, we sampled liver tissue from raccoons (Procyon lotor; n = 37), skunks (Mephitis mephitis; n = 15), and Virginia opossums (Didelphis virginiana; n = 45) euthanized by pest professionals and brown rats (Rattus norvegicus; n = 101) trapped in alleys in Chicago, USA to evaluate how often these species are exposed to ARs. We tested whether mesopredators had a higher prevalence of ARs and to more AR compounds compared to rats and calculated biomagnification factors (mean concentration in mesopredators/rats) as indicators of biomagnification. Of 93 sampled mesopredators, 100 % were exposed to at least one AR compound, mainly brodifacoum (≥80 %), and 79 % were exposed to multiple AR compounds. We also documented teal stomach contents consistent with the consumption of rat bait and altricial young tested positive to the same AR as their mother, suggesting mammary transfer. Of the 101 rats, 74 % tested positive to at least one AR compound and 32 % were exposed to multiple AR compounds. All mesopredator species had biomagnification factors exceeding 1.00 for brodifacoum (6.57–29.07) and bromadiolone (1.08–4.31). Our results suggest widespread exposure to ARs among urban mesopredators and biomagnification of ARs in mesopredators compared to rats. Policies that limit AR availability to non-target species, such as restricting the sale and use of ARs to licensed professionals in indoor settings, education on alternatives, and more emphasis on waste management may reduce health risks for urban wildlife and people in cities around the world.

Anticoagulant rodenticide exposure in common buzzards: Impact of new rules for rodenticide use

Rodenticides are a key component of rodent management strategies, but birds of prey are susceptible to non-target exposure. New rules on sale and use of rodenticide products were introduced across the UK in 2016 in an industry-led stewardship scheme, with the aim of reducing this risk. To determine if this intervention has achieved its aim, exposure to second generation anticoagulant rodenticides (SGARs) was measured in buzzards. Liver samples from 790 buzzards collected between 2005 and 2022 (excluding 2016 and 2017 samples) were analyzed and the percentage presence and concentrations of SGARs from pre-stewardship and post-stewardship samples were compared.There was no statistically significant decrease in the percentage of buzzards exposed to bromadiolone, difenacoum or combined SGAR residues after the introduction of stewardship. The percentage of buzzards exposed to brodifacoum increased significantly post-stewardship, from 8 % to 27 %. There were no significant decreases in the concentrations of individual SGARs post-stewardship but concentration of combined SGARs increased significantly post-stewardship. Individual buzzards were significantly more likely to be exposed to multiple SGARs post-stewardship.Rodenticide poisoning was recorded as the cause of death for 5 % of pre- and post-stewardship buzzards with detectable levels of SGARs, and 90 % of these had combined SGAR residues >0.1 mg/kg.These findings suggest that the industry-led stewardship scheme has not yet had the intended impact of reducing SGAR exposure in non-target wildlife. The study highlights a substantial increase in exposure of buzzards to brodifacoum and to multiple SGARs post-stewardship, indicating that further changes to the stewardship scheme may be necessary.

Drivers of anticoagulant rodenticide exposure in fishers (Pekania pennanti) across the northeastern United States

Studies in parts of Europe, New Zealand, and North America indicate uptake of anticoagulant rodenticides (ARs) by predatory mammals to be widespread and common, with proximity to urban and agricultural areas being an important driver of exposure. Yet, little is known regarding the patterns and drivers of AR exposure in predatory mammals within more forest-dominated landscapes. Across the forest-dominated northeastern United States (US), a region spanning Pennsylvania to Maine, we tested livers from 597 fisher (Pekania pennanti) obtained from the legal harvest for 11 anticoagulant rodenticide compounds. We used kriging to determine potential hot zones (within or among states) and used regression models to test agricultural land use, developed landscapes, and protected areas as potential drivers of exposure patterns. We detected 8 AR compounds, with 78.6% of sampled individuals testing positive for ≥1 compound. The highest rate of exposure was observed in New Hampshire and Vermont at 93.3 and 100.0% and the lowest in Maine at 52.8%. The majority of individuals (55.3%) tested positive for 2-6 different compounds rather than a single compound (23.3%) or none (21.4%), indicating repeated and chronic levels of exposure among fisher. Spatial interpolation revealed a hot region of exposure spanning southern New Hampshire, Vermont, and southeastern New York. Regression models indicated the proportion of wildland-urban intermix (low density buildings within a largely forest-dominated landscape) as a consistent and strong predictor of AR exposure, with marginal and inconsistent relationships observed between AR exposure and the amount of agricultural land use, and with no apparent benefit conferred by protected areas in the region. Given that northeastern states support the highest rural human population density in the nation, with individual homes interspersed throughout a forested matrix, residential use of ARs is implicated as potentially the main driver of exposure for forest carnivores in this region. However, surveillance of a broader suite of species, and greater knowledge of AR use in commercial forestry operations, will be necessary to understand the generality of our observations.

Potential exposure of native wildlife to anticoagulant rodenticides in Gran Canaria (Canary Islands, Spain): Evidence from residue analysis of the invasive California Kingsnake (Lampropeltis californiae)

Anticoagulant rodenticides (ARs), particularly second-generation compounds (SGARs), are extensively used in pest management, impacting non-target wildlife. The California kingsnake (Lampropeltis californiae), an invasive species in Gran Canaria, is under a control plan involving capture and euthanasia. This research aimed to detect 10 different ARs in these snakes, explore geographical and biometrical factors influencing AR exposure, and assess their potential as sentinel species for raptors, sharing similar foraging habits. Liver samples from 360 snakes, euthanized between 2021 and 2022, were analysed for ARs using LC-MS/MS. Results showed all detected rodenticides were SGARs, except for one instance of diphacinone. Remarkably, 90 % of the snakes tested positive for ARs, with over half exposed to multiple compounds. Brodifacoum was predominant, found in over 90 % of AR-positive snakes, while bromadiolone and difenacoum were also frequently detected but at lower levels. The study revealed that larger snakes and those in certain geographic areas had higher AR concentrations. Snakes in less central or more peripheral areas showed lower levels of these compounds. This suggests a correlation between the snakes' size and distribution with the concentration of ARs in their bodies. The findings indicate that the types and prevalence of ARs in California kingsnakes on Gran Canaria mirror those in the island's raptors. This similarity suggests that the kingsnake could serve as a potential sentinel species for monitoring ARs in the ecosystem. However, further research is necessary to confirm their effectiveness in this role.

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.

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

Exposure of wildlife to anticoagulant rodenticides (ARs) has been extensively documented for species directly or indirectly linked to pest rodents via the terrestrial food web. Recently, the scientific focus extended to a former blind spot, namely AR emissions to the aquatic environment, and provided clear evidence of AR residues in freshwater fish. As second-generation ARs are likely to be transferred along the aquatic food chain, a total of 122 Eurasian otter (Lutra lutra) individuals found dead in Germany between 2005 and 2021 were investigated to shed more light on resultant environmental risks. Target analytes comprised one pharmaceutical and eight biocidal anticoagulants, as well as one suspected bait impurity. Notably, all target compounds were detected in the analyzed livers of otters, a primarily piscivorous top predator and indicator species for the aquatic environment, strictly protected by conservation laws. In regions with pronounced rodent control measures, otters were frequently exposed to biocidal ARs. The elevated AR levels measured in multiple otters, compared to freshwater fish, hinted at biomagnification of second-generation ARs within the aquatic food web. The results indicated that risk mitigation measures implemented in Germany within the biocidal product authorization may not be sufficient to protect aquatic non-target wildlife from AR exposure, challenging the effectiveness of current regulatory measures.

Greater predisposition to second generation anticoagulant rodenticide exposure in red foxes (Vulpes vulpes) weakened by suspected infectious disease

Anticoagulant rodenticide (AR) exposure in wild carnivores is a current and global concern due to continuous and widespread use worldwide. We studied the prevalence of ARs in liver samples of 25 red foxes (Vulpes vulpes), 3 European badgers (Meles meles) and 2 genets (Genneta genneta) from Alicante (Spanish Levante region) obtained in 2021 and 2022. In addition to trauma, poisoning by pesticides is the most frequent cause of death in wild carnivores in this region. The present research aims to explain a possible association between the fact of suffering from an infectious disease and the increase in ARs concentrations in the affected animals.Both first- and second-generation ARs were analysed by HPLC/MS/TOF in liver samples. Apart from the cause of death, the influence of other variables such as age, sex and body weight were also assessed on AR liver concentrations. Potential health risks for individuals and populations in the study area have also been studied. Our research detected higher AR concentrations in the group of red foxes clinically diagnosed with infectious disease compared to the group of apparently healthy red foxes, mostly killed by trauma. Furthermore, our results lead us to suggest that red fox could be considered a good sentinel species for the risk of exposure to ARs in other wild mammals. All the livers analysed contained ARs and the most detected compounds in red fox were difenacoum, bromadiolone, brodifacoum, present in all the samples analysed, and flocoumafen (in 96 %). Additionally, 53 % of the animals had at least one second generation anticoagulant rodenticide (SGAR) above the threshold value reported as triggering adverse health effects (200 ng/g). Regarding this, the level of risk in red fox in this area might be classified as high and worrying. Moreover, we suggest that individuals and populations with weakened health due to other diseases (for example, infectious or parasitic diseases) might be more prone to high exposure to anticoagulant rodenticides and, very probably, would be more sensitive to suffering serious effects at lower doses of ARs.

Anthropogenic threats to owls: Insights from rehabilitation admittance data and rodenticide screening in Texas.

Owls (Strigiformes) provide myriad ecosystem services and are sentinels for ecosystem health. However, they are at continued risk from anthropogenic threats such as vehicle collisions, entanglement with human-made materials, and exposure to anticoagulant rodenticides (ARs), a widespread pesticide known to affect owls. Texas is an important region for numerous migratory and non-migratory owl species in the United States (US), yet assessments of threats owls face here are lacking preventing the development of informed conservation strategies. This study coupled assessment of admittance data from two wildlife rehabilitation centers in Texas with AR liver screening to (1) identify which species of owls are commonly admitted, (2) evaluate seasonality of admittance, and (3) assess causes of admittance for owls in Texas. Between 2010 and 2021, 1,620 owls were admitted into rehabilitation, representing eight species of which the Great-horned Owl (Bubo virginianus) was the most common. For all owls combined admittance rates were highest in the spring, driven by an influx of juveniles (n = 703, 43.40%). The leading cause of admittance amongst species was 'no apparent injury' (n = 567, 34.94%). Where clear diagnoses could be made, the leading causes of admittances were 'entrapment in human infrastructure' (n = 100, 6.11%) and 'collision with vehicles' (n = 74, 4.56%). While the admittance data did not reveal any cases of AR poisoning, liver screening demonstrated high incidences of AR exposure; of 53 owls screened for ARs, 50.94% (n = 27) tested positive with 18 showing exposure to multiple ARs. Brodifacoum was the most frequently detected AR (n = 19, 43.18%) and seven owls (25.93%) tested positive within lethal ranges. Our results suggest that owls in Texas are at risk from myriad anthropogenic threats and face high exposure rates to ARs. In doing so, our results can inform conservation strategies that mitigate anthropogenic threats faced by owls in Texas and beyond.

Anticoagulant rodenticides are associated with increased stress and reduced body condition of avian scavengers in the Pacific Northwest

Anticoagulant rodenticides (AR) have been used globally to manage commensal rodents for decades. However their application has also resulted in primary, secondary, and tertiary poisoning in wildlife. Widespread exposure to ARs (primarily second generation ARs; SGARs) in raptors and avian scavengers has triggered considerable conservation concern over their potential effects on populations. To identify risk to extant raptor and avian scavenger populations in Oregon and potential future risk to the California condor (Gymnogyps californianus) flock recently established in northern California, we assessed AR exposure and physiological responses in two avian scavenger species (common ravens [Corvus corax] and turkey vultures [Cathartes aura]) throughout Oregon between 2013 and 2019. AR exposure was widespread with 51% (35/68) of common ravens and 86% (63/73) of turkey vultures containing AR residues. The more acutely toxic SGAR brodifacoum was present in 83% and 90% of AR exposed common ravens and turkey vultures. The odds of AR exposure in common ravens were 4.7-fold higher along the coastal region compared to interior Oregon. For common ravens and turkey vultures that were exposed to ARs, respectively, 54% and 56% had concentrations that exceeded the 5% probability of toxicosis (>20 ng/g ww; Thomas et al., 2011), and 20% and 5% exceeded the 20% probability of toxicosis (>80 ng/g ww; Thomas et al., 2011). Common ravens exhibited a physiological response to AR exposure with fecal corticosterone metabolites increasing with sum ARs (ΣAR) concentrations. Both female common raven and turkey vultures’ body condition was negatively correlated with increasing ΣAR concentrations. Our results suggest avian scavengers in Oregon are experiencing extensive AR exposure and the newly established population of California condors in northern California may experience similar AR exposure if they feed in southern Oregon. Understanding the sources of ARs across the landscape is an important first step in reducing or eliminating AR exposure in avian scavengers.

Interest of the faecal and plasma matrix for monitoring the exposure of wildlife or domestic animals to anticoagulant rodenticides

Anticoagulant rodenticides (ARs), particularly second-generation compounds (SGAR), are known to be a potential threat to unintended species due to their tissue persistence. The liver is the storage tissue of ARs and is a matrix of choice in diagnosing exposure and intoxication of non-target fauna. However, it is only available on dead animals. Blood and faeces can be used on living animals. These two biological matrices were compared in terms of their relevance to exposure to ARs. In addressing this question, we compared the faecal, plasma and liver concentrations of bromadiolone, one of the SGAR frequently implicated in wildlife exposure. We studied this comparison at the individual level and at the population level, considering three influencing factors: dose, sex and time. Our findings demonstrate that faecal analyses are more valuable than plasma analyses for monitoring AR exposure of domestic and wild animals, even if faecal concentrations cannot be correlated with liver concentrations.

Preliminary Evidence of Anticoagulant Rodenticide Exposure in American Kestrels (Falco sparverius) in the Western United States

ABSTRACT Although there is extensive evidence of declines in the American Kestrel (Falco sparverius) population across North America, the cause of such declines remains a mystery. One hypothesized driver of decline is anticoagulant rodenticide (AR) exposure, which could potentially cause mortality or reduced fitness. We investigated AR exposure in wild American Kestrels in Utah, USA. We collected and tested for AR residues in liver samples (n = 8) from kestrels opportunistically encountered dead and in blood samples (n = 71) from live wild kestrels, both nestlings and adults. We found high detection rates in both tissues. Adult kestrels were more likely to exhibit exposure than juveniles sampled in nests. Three-quarters (six of eight) of tested liver samples from adult kestrels exhibited evidence of AR exposure. Additionally, liver samples (n = 19) opportunistically collected from seven species of raptors within our study area had detectable levels of AR residues, with seven of eight raptor species evidencing exposure; across all raptors, five ARs were detected in liver samples, with brodifacoum the most prevalent, being found in over half (14 of 27) of samples. Over half (7 of 12) of the blood samples from adult kestrels had detectible levels of ARs, while only one of 59 juvenile nest samples tested positive. The difference in exposure rates between adults and juveniles could indicate differential exposure pathways by age class. Based on these findings, we recommend that ARs be further investigated as a potential cause of kestrel declines. Future research could focus on expanding sampling to provide sufficient sample sizes to test for potential nonlethal effects of AR exposure (e.g., fecundity, nesting success), identifying potential exposure pathways, and developing methods for passive sampling of ARs in excreta.

Weasel exposure to the anticoagulant rodenticide bromadiolone in agrarian landscapes of southwestern Europe.

Bromadiolone is an anticoagulant rodenticide (AR) commonly used as a plant protection product (PPP) against rodent pests in agricultural lands. ARs can be transferred trophically to predators/scavengers when they consume intoxicated live or dead rodents. ARs exposure in weasels Mustela nivalis, small mustelids specialized on rodent predation, is poorly known in southern Europe. Moreover, in this species there is no information on bioaccumulation of AR diastereomers e.g., cis- and trans-bromadiolone. Trans-bromadiolone is more persistent in the rodent liver and thus, is expected to have a greater probability of trophic transfer to predators. Here, we report on bromadiolone occurrence, total concentrations and diastereomers proportions (trans- and cis-bromadiolone) in weasels from Castilla y León (north-western Spain) collected in 2010-2017, where bromadiolone was irregularly applied to control outbreaks of common voles Microtus arvalis mainly with cereal grain bait distributed by the regional government. We also tested variables possibly associated with bromadiolone occurrence and concentration, such as individual features (e.g., sex), spatio-temporal variables (e.g., year), and exposure risk (e.g., vole outbreaks). Overall bromadiolone occurrence in weasels was 22% (n = 32, arithmetic mean of concentration of bromadiolone positives = 0.072 mg/kg). An individual showed signs of bromadiolone intoxication (i.e., evidence of macroscopic hemorrhages or hyperaemia and hepatic bromadiolone concentration > 0.1 mg/kg). All the exposed weasels (n = 7) showed only trans-bromadiolone diastereomer in liver, whilst a single analyzed bait from those applied in Castilla y León contained trans- and cis-bromadiolone at 65/35%. Bromadiolone occurrence and concentration in weasels varied yearly. Occurrence was higher in 2012 (100% of weasels), when bromadiolone was widely distributed, compared to 2016-2017 (2016: 20%; 2017: 8.33%) when bromadiolone was exceptionally permitted. The highest concentrations happened in 2014 and 2017, both years with vole outbreaks. Our findings indicate that specialist rodent predators could be exposed to bromadiolone in areas and periods with bromadiolone treatments against vole outbreaks.

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.

Anticoagulant rodenticide use in oil palm plantations in Southeast Asia and hazard assessment to non-target animals.

Anticoagulant rodenticides (ARs) are used worldwide for the control of rodent pests and are the main method of control of rat pest populations in agricultural areas. The main aim of this review is to discuss the risk of ARs to non-target wildlife in oil palm areas in Southeast Asia, mainly Indonesia and Malaysia. We discussed AR use in oil palm areas and toxicities of ARs on target and non-target animals. We also reviewed published literature on wildlife species reported in oil palm areas in Southeast Asia and utilizing this information, we assessed the hazard risk of ARs to non-target wildlife in oil palm plantations. ARs are a secondary exposure hazard to rodent-consuming mammalian carnivores, such as leopard cats and civets, and rodent-consuming raptors, such as barn owls. Consumption of dead poisoned prey puts scavengers, such as water monitors, at high risk for AR exposure. Domestic livestock and granivorous birds are at high risk for AR exposure via primary exposure to toxic bait, while omnivores such as macaques and wild pigs are at moderate risk for both primary and secondary exposure to ARs. The effects of ARs on barn owls have been well studied in the field and in laboratory secondary toxicity studies. Thus, the nest-box occupancy and reproductive parameters of local barn owl populations can be monitored as an indicator of the AR exposure level in the area. CLINICAL TRIALS REGISTRATION: No clinical trials were involved in this study.

Toxicological responses to sublethal anticoagulant rodenticide exposure in free-flying hawks.

An important component of assessing the hazards of anticoagulant rodenticides to non-target wildlife is observations in exposed free-ranging individuals. The objective of this study was to determine whether environmentally realistic, sublethal first-generation anticoagulant rodenticide (FGAR) exposures via prey can result in direct or indirect adverse effects to free-flying raptors. We offered black-tailed prairie dogs (Cynomys ludovicianus) that had fed on Rozol® Prairie Dog Bait (Rozol, 0.005% active ingredient chlorophacinone, CPN) to six wild-caught red-tailed hawks (RTHA, Buteo jamaicensis), and also offered black-tailed prairie dogs that were not exposed to Rozol to another two wild-caught RTHAs for 7days. On day 6, blood was collected to determine CPN's effects on blood clotting time. On day 7, seven of the eight RTHAs were fitted with VHF radio telemetry transmitters and the RTHAs were released the following day and were monitored for 33days. Prothrombin time (PT) and Russell's viper venom time confirmed that the CPN-exposed RTHAs were exposed to and were adversely affected by CPN. Four of the six CPN-exposed RTHAs exhibited ptiloerection, an indication of thermoregulatory dysfunction due to CPN toxicity, but no signs of intoxication were observed in the reference hawk or the remaining two CPN-exposed RTHAs. Of note is that PT values were associated with ptiloerection duration and frequency; therefore, sublethal CPN exposure can directly or indirectly evoke adverse effects in wild birds. Although our sample sizes were small, this study is a first to relate coagulation times to adverse clinical signs in free-ranging birds.

Prevalence of anticoagulant rodenticide exposure in red-tailed hawks (Buteo jamaicensis) and utility of clotting time assays to detect coagulopathy.

Anticoagulant rodenticides (ARs) continue to be used across the United States as a method for controlling pest rodent species. As a consequence, wild birds of prey are exposed to these toxicants by eating poisoned prey items. ARs prevent the hepatic recycling of vitamin K and thereby impede the post-translational processing of coagulation factors II, VII, IX, and X that are required for procoagulant complex assembly. Through this mechanism of action, ARs cause hemorrhage and death in their target species. Various studies have documented the persistence of these contaminants in birds of prey but few have attempted to use affordable and accessible diagnostic tests to diagnose coagulopathy in free-ranging birds of prey. In our study free-ranging red-tailed hawks were found to be exposed to difethialone and brodifacoum. Eleven of sixteen (68%) livers tested for AR exposure had detectable residues. Difethialone was found in 1/16 (6%), and brodifacoum was detected in 10/16 (62%) liver samples that were tested for rodenticide residues. Difethialone was found at a concentration of 0.18 ug/g wet weight and brodifacoum concentrations ranged from 0.003-0.234 ug/g wet weight. Two out of 34 (6%) RTHA assessed for blood rodenticide had brodifacoum in serum with measured concentrations of 0.003 and 0.006 ug/g. The range of clotting times in the prothrombin time (PT) and Russell's viper venom time assays for control RTHA were 16.7 to 39.7 s and 11.5 to 91.8 s, respectively. One study bird was diagnosed with clinical AR intoxication with a brodifacoum levels in blood of 0.006 and 0.234 ug/g wet weight in blood and liver respectively, a packed cell volume (PCV) of 19%, and PT and RVVT times of >180 s. No correlation was found between PT and RVVT in the control or free-range RTHA, and there was no relationship found between the presence of liver anticoagulant residues and clotting times in the PT and RVVT.

Asymptomatic Anticoagulant Rodenticide Exposure in Dogs and Cats-A French and Belgian Rural and Urban Areas Study.

Anticoagulant rodenticides (ARs) are important tools for controlling rodent pests, but they also pose a health threat to non-target species. ARs are one of the most common causes of pet poisoning. However, exposure of domestic animals to subclinical doses of ARs is poorly documented. To study the random exposure of dogs and cats to ARs, feces from animals showing no clinical signs of rodenticide poisoning were collected from a network of French and Belgian veterinarians. We analyzed fresh feces from 304 dogs and 289 cats by liquid chromatography-tandem mass spectrometry. This study showed a limited prevalence of AR exposure in dogs and cats of 2.6 and 4.5% respectively. In both species, access to the outdoors is a risk factor for ARs exposure. In contrast, the sex of the animals did not affect the ARs exposure status. The observation of the ratio of cis and trans isomers suggested primary exposure in dogs, but also in some cats. While primary exposure in dogs appears to be related to the use of ARs as plant protection products, primary exposure in cats may be malicious, as warfarin, an anticoagulant formerly used as a rodenticide and now used only in humans, was found in 4 of 13 exposed cats. Secondary exposure may also occur in cats.Our study showed reduced exposure in dogs and cats, compared to wildlife, which often has high exposure, especially in areas where rodent control is important.