Assessment of ruminal degradation, oral bioavailability, and toxic effects of anticoagulant rodenticides in sheep

Difference in coagulation systems of large animal species used in cardiovascular research: a systematic review

Preclinical testing using animal models is indispensable in cardiovascular research. However, the translation to clinical practice of these animal models is questionable since it is not always clear how representative they are. This systematic review intends to summarize the interspecies differences in the coagulation profile of animal models used in cardiovascular research. It aims to guide future research in choosing the optimal animal species. A literature search of PubMed, Embase, Web of Science (Core Collection) and Cochrane Library was performed using a search string that was well defined and not modified during the study. An overview of the search terms used in each database can be found in the appendix. Articles describing coagulation systems in large animals were included. We identified 30 eligible studies of which 15 were included. Compared to humans, sheep demonstrated a less active external pathway of coagulation. Sheep had a higher platelet count but the platelet activatability and response to biomaterials were lower. Both sheep and pigs displayed no big differences in the internal coagulation system compared to humans. Pigs showed results very similar to those of humans, with the exception of a higher platelet count and stronger platelet aggregation in pigs. Coagulation profiles of different species used for preclinical testing show strong variation. Adequate knowledge of these differences is key in the selection of the appropriate species for preclinical cardiovascular research. Future thrombogenicity research should compare sheep to pig in an identical experimental setup.

Acute hemorrhage and death in calves following chlorophacinone exposure

Three calves were submitted to the Iowa State University Veterinary Diagnostic Laboratory for diagnostic evaluation following an abrupt increase in morbidity and mortality in a calf herd associated with epistaxis and widespread hemorrhage. Each of the submitted calves had moderate-to-severe hemorrhage within various tissues and body cavities, including the thymus, subcutaneous region of the neck, mediastinum, lungs, pericardial sac, heart, spleen, perirenal fat, urinary bladder, and skeletal muscle, including the diaphragm. An anticoagulant rodenticide screen was performed on the livers of each calf. Significant concentrations of chlorophacinone were detected at 4.2, 3.6, and 2.9 ppm in liver. Multiple piles and an open pail of white powdery material were present within the facility in which the calves were housed and were identified as the sources of chlorophacinone. Acute hemorrhage and death occurred in fourteen 1.5-mo-old, crossbred calves following ingestion of the vitamin K antagonist chlorophacinone.

Anticoagulant rodenticide ingestion: Who will develop coagulopathy?

Introduction:

Development of coagulopathy after anticoagulant rodenticide ingestion varies among patients. This study aimed to identify factors that were associated with coagulopathy after anticoagulant rodenticide ingestion.

Methods:

This was a retrospective cohort study, conducted in the Hong Kong Poison Information Centre. All patients who reported rodenticide exposure and presented to the Accident and Emergency Department from 1 January 2010 to 31 December 2019 were recruited. Coagulopathy was defined as International Normalized Ratio of 1.3 or above.

Results:

One hundred sixty-nine patients were included in the final analysis. The median age was 44 years old. Forty-nine patients developed coagulopathy (International Normalized Ratio ⩾1.3). Univariate analysis (at p < 0.05) showed that age (p = 0.003), ingestion of first-generation anticoagulant rodenticide (p = 0.017), ingestion of more than one pack (p < 0.001), intentional ingestion (p = 0.002), hypoalbuminemia (p < 0.001), elevated alanine aminotransferase level (p = 0.041) and abnormal estimated glomerular filtration rate (p = 0.005) on presentation, and co-ingestion with paracetamol (p = 0.018) were associated with coagulopathy after anticoagulant rodenticide ingestion. Among these, ingestion of more than one pack (p < 0.001; odds ratio = 19.8; 95% confidence interval = 6.78–65.7), ingestion of first-generation anticoagulant rodenticide (p = 0.006; odds ratio = 5.2; 95% confidence interval = 1.96–15.2), hypoalbuminemia (p < 0.001; odds ratio = 22.4; 95% confidence interval = 6.17–99.0) and elevated alanine aminotransferase level on presentation (p = 0.039; odds ratio = 7.11; 95% confidence interval = 1.58–33.1) were statistically significant in the multivariate analysis.

Conclusion:

Ingestion of more than one pack and ingestion of first-generation anticoagulant rodenticides were significantly associated with the development of coagulopathy after anticoagulant rodenticide ingestion. Patients who developed hypoalbuminemia or elevated alanine aminotransferase level as a result of anticoagulant rodenticide ingestion were also significantly associated with the development of coagulopathy.

Biomarkers Potency to Monitor Non-target Fauna Poisoning by Anticoagulant Rodenticides

The widespread use of pesticides to control agricultural pests is a hot topic on the public scene of environmental health. Selective pest control for minimum environmental impact is a major goal of the environmental toxicology field, notably to avoid unintended poisoning in different organisms. Anticoagulant rodenticides cause abnormal blood coagulation process; they have been widely used to control rodents, allowing inadvertent primary and secondary exposure in domestic animals and non-target predatory wildlife species through direct ingestion of rodenticide-containing bait or by consumption of poisoned prey. To report toxic effect, the most common approach is the measurement of liver or plasma residues of anticoagulant rodenticides in dead or intoxicated animals showing clinical symptoms. However, one major challenge is that literature currently lacks a hepatic or plasma concentration threshold value for the differentiation of exposure from toxicity. Regarding the variation in pharmacology properties of anticoagulant rodenticides inter- and intra-species, the dose-response relationship must be defined for each species to prejudge the relative risk of poisoning. Beyond that, biomarkers are a key solution widely used for ecological risk assessment of contaminants. Since anticoagulant rodenticides (AR) have toxic effects at the biochemical level, biomarkers can serve as indicators of toxic exposure. In this sense, toxicological knowledge of anticoagulant rodenticides within organisms is an important tool for defining sensitive, specific, and suitable biomarkers. In this review, we provide an overview of the toxicodynamic and toxicokinetic parameters of anticoagulant rodenticides in different animal species. We examine different types of biomarkers used to characterize and differentiate the exposure and toxic effects of anticoagulant rodenticide, showing the strengths and weaknesses of the assays. Finally, we describe possible new biomarkers and highlight their capabilities.

Permanent Bilateral Carotid Filters for Stroke Prevention in Atrial Fibrillation

Purpose of Review

A novel permanent carotid filter device for percutaneous implantation was developed for the purpose of stroke prevention. In this review, we cover rationale, existing preclinical and clinical data, and potential future directions for research using such a device.

Recent Findings

The Vine™ filter was assessed for safety in sheep and in 2 observational human studies, the completed CAPTURE 1 (n = 25) and the ongoing CAPTURE 2 (planned n = 100). CAPTURE 1 has shown high procedural and long-term implant safety. A control group was not available for comparison.

Summary

A mechanical filter for permanent stroke prevention can be implanted bilaterally in the common carotid artery safely and efficiently. A randomized trial is planned for 2021 (n = 3500, INTERCEPT) to demonstrate superiority of a filter + anticoagulation strategy over anticoagulation alone in patients at high risk for ischemic stroke.

Accidental chlorophacinone exposure of lactating ewes: Clinical follow-up and human health dietary implications

Anticoagulant rodenticides are widely used for rodent control in agricultural and urban settings. Their intense use can sometimes result in accidental exposure and even poisoning of livestock. Can milk, eggs or meat derived from such accidently exposed animals be consumed by humans? Data on the pharmacokinetics of chlorophacinone in milk of accidently exposed ewes were used to estimate the risk associated with its consumption. Three days after accidental ingestion, chlorophacinone was detected in plasma of 18 ewes, with concentrations exceeding 100 ng/mL in 11 animals. Chlorophacinone was detected in milk on day 2 post-exposure and remained quantifiable for at least 7 days in milk of these 11 ewes. Concentrations in milk were much lower than in plasma and decreased quickly (mean half-life of 2 days). This study demonstrated dose-dependent mammary transfer of ingested chlorophacinone. Variation in prothrombin time (PT) on Day 3 suggested that some of the ewes that ingested chlorophacinone may have been adversely affected, but PT did not facilitate estimation of the quantity of chlorophacinone consumed. Using safety factors described in the literature, consumption of dairy products derived from these ewes after a one-week withdrawal period would pose low risk to consumers.

Local context and environment as risk factors for acute poisoning in animals in northwest Italy

Animal and bait poisoning data for northwest Italy collected between 2012 and 2017 were described and analyzed to estimate the risk of exposure to hazardous substances by animals. In about 4% of animals necropsied (n = 356/9512), the cause of death was poisoning and domestic pets (9.5%) and synanthropic animals (12.2%) appear to be the most involved. Furthermore, 294 out of 728 baits (40.4%) were positive for toxic substances and/or inert hazardous material. Application of a mixed-effects Poisson regression model and local cluster analysis evidenced increased risk of exposure to poisoning with altimetry (>600 m.a.s.l.) and municipality (PR = 1.6, 95%CI 1.2-2.1 for poisoning, PR = 2.2, 95%CI 1.2-4.2 for poisoning by insecticides and PR = 2.9, 95%CI 1.4-6.2 for poisoning by metaldehyde). Since the mountainous areas in the region are mostly devoted to pasture and extensive farming, the high frequency of animal and bait poisoning events may be related to farmers' need to protect their livestock and crops against foxes, wolves, rodents or wild boars. Summarizing, the type of land use and context may influence the frequency and type of toxin chosen to kill animals considered a nuisance for hunting, farming, agriculture and apiculture. Despite bans and limitations, the use of harmful substances is not perceived as an environmental threat but rather as routine pest control. Animal and bait poisoning constitute a public health concern because it is potentially harmful to humans and the environment. Our findings may inform risk communication strategies, as well as prevention and control measures for the reduction of illegal and non-targeted species poisoning.

Long term performance evaluation of small-diameter vascular grafts based on polyvinyl alcohol hydrogel and dextran and MSCs-based therapies using the ovine pre-clinical animal model

The functional and structural performance of a 5cm synthetic small diameter vascular graft (SDVG) produced by the copolymerization of polyvinyl alcohol hydrogel with low molecular weight dextran (PVA/Dx graft) associated to mesenchymal stem cells (MSCs)-based therapies and anticoagulant treatment with heparin, clopidogrel and warfarin was tested using the ovine model during the healing period of 24 weeks. The results were compared to the ones obtained with standard expanded polyetetrafluoroethylene grafts (ePTFE graft). Blood flow, vessel and graft diameter measurements, graft appearance and patency rate (PR), thrombus, stenosis and collateral vessel formation were evaluated by B-mode ultrasound, audio and color flow Doppler. Graft and regenerated vessels morphologic evaluation was performed by scanning electronic microscopy (SEM), histopathological and immunohistochemical analysis. All PVA/Dx grafts could maintain a similar or higher PR and systolic/diastolic laminar blood flow velocities were similar to ePTFE grafts. CD14 (macrophages) and α-actin (smooth muscle) staining presented similar results in PVA/Dx/MSCs and ePTFE graft groups. Fibrosis layer was lower and endothelial cells were only detected at graft-artery transitions where it was added the MSCs. In conclusion, PVA/Dx graft can be an excellent scaffold candidate for vascular reconstruction, including clinic mechanically challenging applications, such as SDVGs, especially when associated to MSCs-based therapies to promote higher endothelialization and lower fibrosis of the vascular prosthesis, but also higher PR values.

VIGILANCE POISON: Illegal poisoning and lead intoxication are the main factors affecting avian scavenger survival in the Pyrenees (France)

A specific surveillance program has been set up to monitor avian scavenger populations in the French Pyrenean Mountains, hosting a high proportion of the French populations. The two main purposes of the study were to identify all causes of death and to investigate poisoning cases. All 170 birds found dead during the 7-year program were submitted to full necropsy, X-Ray, parasitological investigations and consistent analytical toxicology screenings (Cholinesterase inhibitors, anticoagulant rodenticides, organochlorine insecticides, Pb, Cd). Over the study period, 8 Bearded Vultures, 120 Griffon Vultures, 8 Egyptian Vultures and 34 Red kites were eventually collected. Mortality events were often multifactorial, but poisoning was by far the most common cause of death (24.1%), followed by trauma/fall (12%), bacterial diseases and starvation (8%) and electrocution (6%). Illicit use of banned pesticides was identified as a common cause of poisoning (53% of all poisoning cases) and lead poisoning was also identified as a significant toxicant issue (17% of all poisoning cases). Lead isotopic signature could be associated primarily with ammunition. Last, a positive association between trauma and lead contamination was detected, indicating that lead could be a significant contributor to different causes of death. These results urge for severe restrictions on the use of lead ammunition to prevent scavengers from detrimental exposure.

Bioaccumulation of chlorophacinone in strains of rats resistant to anticoagulants

BACKGROUND

Anticoagulants are the only available compounds in the EU to control rat populations. Resistance to anticoagulant rodenticides (antivitamin K or AVK) is described and widespread across Europe. The present objective was to determine whether resistance was associated with an increased potential for bioaccumulation of AVK in the liver. Rats were selected from three major resistant genetically identified strains across Europe: Y139C (Germany), Y139F (France) and L120Q (United Kingdom). The rats were housed in individual cages and fed chlorophacinone wheat bait (50 mg kg(-1) ). Animals were assigned to groups for euthanasia either on day 1, 4, 9 or 14 (resistant rats) or on days 1 and 4 (susceptible rats).

RESULTS

Chlorophacinone accumulated from day 1 to day 4 in all strains (maximum 160 µg liver(-1)) and remained stable thereafter. There was no significant difference between strains. Extensive metabolism of chlorophacinone was also found, and was similar (in nature and proportion of metabolites) across strains (3 OH-metabolites identified). Only the survival time differed significantly (L120Q > Y139C = Y139F > susceptible).

CONCLUSIONS

Accumulation of chlorophacinone occurs from day 1 to day 4, and an equilibrium is reached, suggesting rapid elimination. Resistant and susceptible rats accumulate chlorophacinone to the same extent and only differ in terms of survival times. Resistant rats may then be a threat for non-target species for prolonged periods of time.

Are water vole resistant to anticoagulant rodenticides following field treatments?

The anti-vitamin Ks (AVKs) are widely used to control rodent populations. They inhibit Vitamin K regeneration by the Vitamin K Epoxide Reductase (VKOR) and cause a fatal hemorrhagic syndrome. Because of repeated use, some populations of commensal rodents have expressed resistance to these compounds. In Franche-Comté (France), the water vole exhibits cyclic population outbreaks. A second generation AVK, bromadiolone, has been used for the last 20 years to control vole populations. The aim of this study is to determine whether these repeated treatments could have led to the development of resistance to AVKs in water vole populations. We conducted enzymatic and genetic studies on water voles trapped in treated and non treated plot. The results indicate that voles from the most heavily treated area exhibit enzymatic changes in VKOR activity hence arguing for resistance to AVKs and that an intronic haplotype on the vkorc1 gene seems to be associated with these enzymatic changes.

Prevalence of anticoagulant rodenticide poisoning in humans and animals in France and substances involved

INTRODUCTION

Anticoagulant rodenticides have been used for over 50 years to control rodent populations. Since their first introduction, resistance developed in rodents, and second-generation products, more active but also more toxic, have been marketed. These compounds are currently being reviewed under European Regulations.

METHODS

The purpose of this work is to describe anticoagulant poisoning based on retrospective data from French human and animal poison control centers. Cases from 2004 to 2007 were collected.

RESULTS

Overall, the proportion of anticoagulant exposure reported to the Lyon poison control center appeared very limited and mostly occurred in young children, with no or very limited clinical severity. Some cases also occurred after intentional use of anticoagulants in adults. Circumstances of exposure are predominantly accidental in man (77%). In animals, both domestic and wild species, anticoagulant exposure seems more common, and often more accompanied by clinical signs. Among domestic species, dogs represent over 60% of the cases: in wildlife hares and rabbits account for almost 50% of the submitted cases, followed by predators and scavengers.

CONCLUSION

Rodenticides involved are representative of the market share of anticoagulants, for human and domestic animal exposures. In wildlife, bromadiolone and chlorophacinone are by far the most important products, being the only ones registered for field use. There is no report of mortality in the human data, and less than 1% of all exposure cases in domestic animals were fatal.

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

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

Organochlorine pesticides, PCBs, heavy metals and anticoagulant rodenticides in tissues of Eurasian otters (Lutra lutra) from upper Loire River catchment (France)

In this study, tissues of the Eurasian otter (Lutra lutra) from a naturally expanding population along upper Loire River (France) catchment were used for contaminants analyses. nine organochlorine pesticides, 16 PCB congeners, five heavy metals (lead, cadmium, mercury, copper and arsenic) and three anticoagulant rodenticides were quantified in livers of road-traffic killed otters. Organochlorine compounds and heavy metals were found in 100% of the samples, and occasional contamination by anticoagulant rodenticides was confirmed. Total organochlorine pesticides reached a maximum of 9.4 mg kg(-1) lipid weight. Higher data were observed for other contaminants, especially total PCBs and mercury. Maximal total PCBs values reached 64.8 mg kg(-1) lipid weight, and maximal measured mercury concentration was 8.2 mg kg(-1) fresh weight. Considering the expansion noted in the study area, global contamination does not seem to threat the short-term species conservation. Nevertheless, important values at some individual scale were noticed, suggesting high inter-individual variations in populations.

Residues in Brandt's voles (Microtus brandti) exposed to bromadiolone-impregnated baits in Mongolia

In 2002, hundreds of non-target wildlife deaths occurred in Mongolia following aerial applications of bromadiolone, an anticoagulant rodenticide, to control eruptive Brandt's vole (Microtus brandti) populations. To clarify whether secondary poisoning could have contributed to these deaths, a field study was undertaken in Mongolia to measure bromadiolone residues in voles following exposure to two concentrations (50 and 500 mg/kg) of bromadiolone-treated wheat. The two treatments produced different total burdens (2.65 microg+/-0.53SE and 13.70 microg+/-3.82SE, respectively) and liver burdens (1.74 microg+/-0.33SE and 8.81 microg+/-2.33SE, respectively) of bromadiolone in voles (both p<0.05). Total burdens of bromadiolone in voles found dead above ground were higher than those of live-trapped voles (32.35 microg+/-17.98SE versus 5.18 microg+/-1.40SE, respectively; p<0.05). These results are valuable for future assessments of secondary poisoning risk to scavengers and predators from large-scale bromadiolone poisoning operations of the type undertaken in Mongolia.

Animal poisoning in Europe. Part 3: Wildlife

This review article is the third in a series on animal poisoning in Europe and represents a collation of published and non-published wildlife poisoning data from Belgium, France, Greece, Italy and Spain over the last 10 years. Birds, particularly waterfowl and raptors, were more commonly reported as victims of poisoning than wild mammals. In addition to specific but important toxicological disasters, deliberate primary or secondary poisonings are of concern to all countries. Metals (particularly lead arising from sporting/hunting activities) and pesticides (mainly anticholinesterases and anticoagulants) are frequent causes of poisoning, and often have fatal consequences. A more unified and consistent approach throughout European countries to improve the reporting and the analytical confirmation of wildlife poisoning would help to reduce the number of cases of malicious or negligent animal poisoning.

Pesticides and the intoxication of wild animals

Pesticides are widely used to control agricultural pests. Unfortunately, because of their biological activity, they may have detrimental effects on nontarget species. Acute toxicity, resulting in death, is reported worldwide. Although chronic and indirect effects may be even more hazardous for animal populations on a long-term basis, they are usually evaluated as parts of research programs. The purpose of this paper was to review the wildlife-poisoning surveillance systems and their results regarding the circumstances of exposure of wild animals, the pesticides involved and the species exposed. Most data are retrieved from the British and French pesticide poisoning surveillance systems in wildlife, with some data from other European structures.

Persistence of bromadiolone anticoagulant rodenticide in Arvicola terrestris populations after field control

This paper documents the exposure pattern of a population of small mammals to bromadiolone over time in a field-scale follow up. This is the first assessment of the field-scale effect of such control operation on the availability of bromadiolone-exposed A. terrestris prey to nontarget predator species. It indicates that an important risk of poisoning of nontarget species does exist during large-scale field control operations with bromadiolone, which is contradictory to results obtained from laboratory experiments in the early 1980s and consistent with the secondary poisoning hazards due to repeated exposure regularly reported during the past 20 years.