Coagulopathic effects and therapy of brodifacoum toxicosis in dogs

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.

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.

Continued Anticoagulant Rodenticide Exposure of Red-tailed Hawks (Buteo jamaicensis) in the Northeastern United States with an Evaluation of Serum for Biomonitoring

Prior studies (2006-2016) in birds of prey admitted to a wildlife clinic in Massachusetts, USA, revealed widespread exposure to second-generation anticoagulant rodenticides (SGARs) among red-tailed hawks (Buteo jamaicensis, RTHAs). Continued monitoring of species for which historic data are available can reveal trends in exposure that aid in evaluating the effectiveness of risk-mitigation measures. While the majority of exposure-monitoring studies utilize liver tissue collected postmortem, antemortem modalities, such as serum analysis, may be desirable for risk assessments in certain populations. However, the sensitivity of serum for detecting anticoagulant rodenticides (ARs) is not well studied. Paired liver and serum samples from 43 RTHAs were evaluated from 2017 to 2019. In liver tissue, 100% of birds were positive for ARs, with the SGARs brodifacoum, bromadiolone, and difethialone identified most frequently; 91% of birds had liver residues of 2 to 4 ARs. These findings represent the highest exposure both to ARs overall and to multiple ARs in RTHAs compared to previous studies. All birds diagnosed with AR toxicosis (n = 14) were positive for ARs in serum; however, all subclinically exposed birds (n = 29) were negative in serum. These data show that exposure to SGARs remains widespread in RTHAs in this geographic area. In addition, although serum analysis is not sensitive for detecting sublethal exposures in RTHAs, it can potentially support a diagnosis of AR toxicosis in conjunction with other consistent signs. Environ Toxicol Chem 2020;39:2325-2335. © 2020 SETAC.

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.

Helicobacter pylori antibiotic eradication coupled with a chemically defined diet in INS-GAS mice triggers dysbiosis and vitamin K deficiency resulting in gastric hemorrhage

Infection with Helicobacter pylori causes chronic inflammation and is a risk factor for gastric cancer. Antibiotic treatment or increased dietary folate prevents gastric carcinogenesis in male INS-GAS mice. To determine potential synergistic effects, H. pylori-infected male INS-GAS mice were fed an amino acid defined (AAD) diet with increased folate and were treated with antibiotics after 18 weeks of H. pylori infection. Antibiotic therapy decreased gastric pathology, but dietary folate had no effect. However, the combination of antibiotics and the AAD diet induced anemia, gastric hemorrhage, and mortality. Clinical presentation suggested hypovitaminosis K potentially caused by dietary deficiency and dysbiosis. Based on current dietary guidelines, the AAD diet was deficient in vitamin K. Phylloquinone administered subcutaneously and via a reformulated diet led to clinical improvement with no subsequent mortalities and increased hepatic vitamin K levels. We characterized the microbiome and menaquinone profiles of antibiotic-treated and antibiotic-free mice. Antibiotic treatment decreased the abundance of menaquinone producers within orders Bacteroidales and Verrucomicrobiales. PICRUSt predicted decreases in canonical menaquinone biosynthesis genes, menA and menD. Reduction of menA from Akkermansia muciniphila, Bacteroides uniformis, and Muribaculum intestinale were confirmed in antibiotic-treated mice. The fecal menaquinone profile of antibiotic-treated mice had reduced MK5 and MK6 and increased MK7 and MK11 compared to antibiotic-free mice. Loss of menaquinone-producing microbes due to antibiotics altered the enteric production of vitamin K. This study highlights the role of diet and the microbiome in maintaining vitamin K homeostasis.

Determination of anticoagulant rodenticides in faeces of exposed dogs and in a healthy dog population

Background

Exposure to anticoagulant rodenticides (ARs) in dogs is among the most common causes of poisoning in small animal practice, but information about toxicokinetic of these rodenticides in dogs is lacking. We analysed blood and faeces from five accidentally exposed dogs and 110 healthy dogs by reversed phase ultra-high performance liquid chromatography-tandem mass spectrometry. The aim of the study was to estimate elimination of brodifacoum, bromadiolone and difenacoum after acute exposure, calculate the half-lives of these rodenticides in dogs, estimate faecal elimination in a litter of puppies born, and further to identify the extent of AR exposure in a healthy dog population.

Results

Three dogs were included after single ingestions of brodifacoum; two dogs ingested bromadiolone and one dog ingested difenacoum. Maximum concentrations in faeces were found after day 2–3 for all ARs. The distribution half-lives were 1–10 days for brodifacoum, 1–2 days for bromadiolone and 10 days for difenacoum. Brodifacoum and difenacoum had estimated terminal half-lives of 200–330 days and 190 days, respectively. In contrast, bromadiolone had an estimated terminal half-life of 30 days. No clinical signs of poisoning or coagulopathy were observed in terminal elimination period. In blood, the terminal half-life of brodifacoum was estimated to 8 days. Faeces from a litter of puppies born from one of the poisoned dogs were examined, and measurable concentrations of brodifacoum were detected in all samples for at least 28 days after parturition. A cross-sectional study of 110 healthy domestic dogs was performed to estimate ARs exposure in a dog population. Difenacoum was detected in faeces of one dog. Blood and faecal samples from the remaining dogs were negative for all ARs.

Conclusions

Based on the limited pharmacokinetic data from these dogs, our results suggest that ARs have a biphasic elimination in faeces using a two-compartment elimination kinetics model. We have shown that faecal analysis is suitable and reliable for the assessment of ARs exposure in dogs and a tool for estimating the AR half-lives. Half-lives of ARs could be a valuable indicator in the exposed dogs and provides important information for veterinarians monitoring AR exposure and assessment of treatment length in dogs.

Acute toxicity and clotting times of anticoagulant rodenticides to red-toothed (Odonus niger) and black (Melichthys niger) triggerfish, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides)

Anticoagulant rodenticides (ARs) are used in rat eradication efforts on island wildlife refuges. AR bait pellets can get into coral reef areas during broadcasting and lead to exposure of non-target organisms, such as marine fishes. The objective of this study was to determine the sensitivity of representative saltwater fishes, Red-toothed triggerfish (Odonus niger) and Black triggerfish (Melichthys niger), and common freshwater fishes, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides) to first generation ARs, diphacinone (DPN) and chlorophacinone (CPN), as well as a second-generation AR, brodifacoum (BROD). Acute toxicity of ARs was evaluated by single dose, intraperitoneal injections. The median lethal dose (LD50) ranges were 137-175 μg DPN/g, 155-182 μg CPN/g, and 36-48 μg BROD/g for Red-toothed triggerfish and 90-122 μg DPN/g, 125-164 μg CPN/g, and 50-75 μg BROD/g for black triggerfish. Laboratory surrogate test fish species fathead minnow and largemouth bass were of similar sensitivity toward AR-induced toxicity compared to triggerfish based on LD50 values. Sublethal effects on elevated clotting time occurred in dose-dependent fashion in all fish tested. Fish appear to have low sensitivity to AR chemicals as compared to other taxa, in particular mammals and birds, based on across-taxa comparisons of species sensitivity distributions of whole body, single dose acute lethality (LD50 values). The sensitivity of fish to waterborne exposures of ARs has yet to be fully evaluated and indeed may prove more hazardous to fish.

Intravenous vitamin K1 normalises prothrombin time in 1 hour in dogs with anticoagulant rodenticide toxicosis

Four dogs with anticoagulant rodenticide toxicosis were treated with intravenous vitamin K₁ in lieu of plasma transfusion due to client cost constraints. Two dogs experienced a suspected anaphylactoid reaction, necessitating cessation of the treatment in one dog. Prothrombin time was rechecked 1 h after treatment in the remaining three dogs and all results were within the normal reference range. All four dogs were discharged from hospital within 48 h of presentation. Intravenous vitamin K₁ rapidly reverses the coagulopathic state in dogs with anticoagulant rodenticide toxicosis. It is a viable alternative therapy to plasma transfusion if circumstances preclude its use; however, patients must be monitored for anaphylactoid reactions.

Quantitative method for analysis of six anticoagulant rodenticides in faeces, applied in a case with repeated samples from a dog

Background

Accidental poisoning with anticoagulant rodenticides is not uncommon in dogs, but few reports of the elimination kinetics and half-lives in this species have been published. Our objectives were to develop and validate a new method for the quantification of anticoagulant rodenticides in canine blood and faeces using reversed phase ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) and apply the method on a case of anticoagulant rodenticide intoxication.

Results

Sample preparation was liquid–liquid extraction. Six anticoagulant rodenticides were separated using a UPLC^® BEH C₁₈-column with a mobile phase consisting of 5 mM ammonium formate buffer pH 10.2 and methanol. MS/MS detection was performed with positive electrospray ionization and two multiple reaction monitoring transitions. The limits of quantification were set at the levels of the lowest calibrator (1.5–2.7 ng/mL or ng/g). The method was successfully applied to a case from a dog accidentally poisoned with anticoagulant rodenticide. Coumatetralyl and brodifacoum concentrations were determined from serial blood and faecal samples. A terminal half-life of at least 81 days for coumatetralyl in blood was estimated, which is longer than previous reported in other species. A slow elimination of brodifacoum from the faeces was found, with traces still detectable in the faeces at day 513.

Conclusions

This study offers a new method of detection and quantification of six frequently used anticoagulant rodenticides in canine faeces. Such drugs might cause serious health effects and it is important to be able to detect these drugs, to initiate proper treatment. The very long elimination half-lives detected in our study is important to be aware of in assessment of anticoagulant rodenticide burden to the environment.

An apparent case of brodifacoum toxicosis in a whelping dog

A 7-y-old Weimaraner bitch was presented to emergency service after 3 h of active labor with no puppies produced. Hemoabdomen and hemothorax were present at the time of surgery; prothrombin time (PT) and activated partial thromboplastin time (aPTT) were both found to be within normal ranges. Surgical cesarean section was performed; 4 dead puppies and 5 live puppies were delivered. Because hemostasis was difficult to achieve, a hysterectomy was performed; however, the dog died as the operation was being completed. At autopsy, the pleural cavity contained 1.5 L of unclotted blood; the peritoneal cavity was relatively normal, and no obvious hemorrhage was associated with the surgical sites. All 4 dead fetuses were opened, and their pleural cavities were filled with unclotted blood. An anticoagulant screen was performed, and brodifacoum was identified in the liver of the bitch. This case is unusual in that the PT and aPTT were within reference intervals, but brodifacoum was present in sufficient amounts to potentially result in this dog bleeding to death, and also is suspected to have crossed the placenta and caused hemothorax and death in 4 of 9 puppies in utero.

Comparison of albumin, colloid osmotic pressure, von Willebrand factor, and coagulation factors in canine cryopoor plasma, cryoprecipitate, and fresh frozen plasma

OBJECTIVE

To compare albumin concentrations, coagulation factors activity, and colloid osmotic pressure (COP) of cryoprecipitate (CRYO) and cryopoor plasma (CPP) to that of source fresh frozen plasma (FFP).

DESIGN

Prospective in vitro study.

SETTING

University teaching hospital.

ANIMALS

Ten healthy, non-Greyhound dogs enrolled in an academic teaching hospital blood donor program.

INTERVENTIONS

Fresh blood was obtained from canine blood donors and separated into FFP and packed red blood cells. The source FFP was further separated into CRYO and CPP. Albumin and fibrinogen concentrations, COP, activities of coagulation factors II, V, VII, VIII, IX, X, and von Willebrand factor (vWf) were assessed for each FFP, CRYO, and CPP.

MEASUREMENTS AND MAIN RESULTS

The mean albumin concentration and COP in CPP were significantly higher compared with those found in FFP, with 31.7 g/L (±6) in CPP compared to 28.9 g/L (±0.5) in FFP (P < 0.001) and 14.5 mm Hg (±0.7) in CPP compared to 12.7 mm Hg (±0.3) in FFP (P = 0.03), respectively. CRYO had significantly higher concentrations of fibrinogen (median 3.46 g/L, 95% CI 2.65-4.27), and higher activities of factor VIII (mean activity 427.0%, ±95.4) and vWf (mean activity 504.7%, ±41.39) as compared to the other products. The activities of vitamin K dependent factors II, VII, and X were similar in CPP compared to FFP, although factor IX activity was lower in CPP. There was no significant difference in factor II or VII activities between the 3 products.

CONCLUSIONS

The mean albumin concentration and COP were highest in CPP, suggesting that CPP may be a potential alternative to FFP for oncotic support and albumin replacement. CRYO contained higher activities of vWf and factor VIII than other products and could be used to treat vWf deficiency and hemophilia A. As vitamin K dependent coagulation factors II, VII, and X in CPP were similar to FFP, CPP may be an option for replacement of most of vitamin K dependent factors.

Recovery of brodifacoum in vomitus following induction of emesis in dogs that had ingested rodenticide bait

AIM

To assess the benefit of inducing emesis in dogs that have ingested rodenticide bait containing brodifacoum (BDF), by determining the amount of BDF in bait recovered from the vomitus relative to the estimated amount consumed.

METHODS

Between 2014 and 2015 samples of vomitus from seven dogs that ingested rodenticide baits containing BDF were submitted by veterinarians in New Zealand. All seven dogs had been given apomorphine by the veterinarian and vomited within 1 hour of ingesting the bait. Some or all of the bait particles were retrieved from each sample and were analysed for concentrations of BDF using HPLC. Based on estimations of the mass of bait consumed, the concentration of BDF stated on the product label, and the estimated mass of bait in the vomitus of each dog, the amount of BDF in the vomited bait was calculated as a percentage of the amount ingested.

RESULTS

For five dogs an estimation of the mass of bait ingested was provided by the submitting veterinarian. For these dogs the estimated percentage of BDF in the bait retrieved from the vomitus was between 10-77%. All dogs were well after discharge but only one dog returned for further testing. This dog had a normal prothrombin time 3 days after ingestion.

CONCLUSIONS AND CLINICAL RELEVANCE

The induction of emesis within 1 hour of ingestion can be a useful tool in reducing the exposure of dogs to a toxic dose of BDF. The BDF was not fully absorbed within 1 hour of ingestion suggesting that the early induction of emesis can remove bait containing BDF before it can be fully absorbed.

Upper Airway Obstruction Secondary to Anticoagulant Rodenticide Toxicosis in Five Dogs

Five dogs were presented with clinical signs compatible with upper airway obstruction, including stridor, stertor, coughing, gagging, and varying degrees of respiratory distress. All dogs had radiographic findings of soft tissue opacity in the area of the pharynx, larynx, or trachea, and several had narrowing of the tracheal lumen. Coagulation abnormalities (prolonged prothrombin time, activated partial thromboplastin time) were present in the four dogs that underwent testing. Four of five dogs were treated for the coagulopathy, presumably due to anticoagulant rodenticide toxicosis, and survived to discharge.Upper airway obstruction is an unusual presentation for anticoagulant rodenticide toxicosis in dogs. Raising the index of suspicion for this treatable condition may help clinicians to identify this sooner.

Anticoagulant rodenticide screening in dogs: 123 cases (1996-2003)

OBJECTIVE

To identify dogs with anticoagulant rodenticide (AR) screens submitted, determine whether detected concentrations of the anticoagulants correlated with severity of clinical signs for dogs with positive results on AR screens, and identify the most common disease processes present and the prognosis for those with negative AR screens.

DESIGN

Retrospective case series.

ANIMALS

123 dogs.

PROCEDURES

History, signalment, clinical signs, physical examination findings, PCV, total solids concentration, prothrombin time, activated partial thromboplastin time, platelet count, AR concentrations, duration of hospitalization, blood products administered, final diagnosis, and outcome were recorded from medical records of dogs that underwent AR toxicology screenings.

RESULTS

75 of 123 (60.9%) dogs tested positive for AR. Dogs tested positive for brodifacoum, diphacinone (also called diphenadione), and chlorophacinone. Dogs with positive AR screenings weighed significantly less, received significantly more fresh frozen plasma, had significantly longer initial prothrombin time, and were significantly more likely to survive, compared with those with negative screens. Anticoagulant rodenticide concentrations ranged from trace amounts to 1,120 parts per billion and were not correlated with any recorded parameter. The most common conditions diagnosed in the 48 dogs with negative screens included neoplasia in 15 (31.3%), immune-mediated disease in 7 (14.6%), and gastrointestinal bleeding in 5 (10.4%) dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

AR concentrations were not correlated with severity of clinical signs or the degree of prolongation of coagulation times in this series of patients. Patients with severe coagulopathies but negative results of AR screening had a poor prognosis, with neoplasia as the most common diagnosis. Anticoagulant rodenticide intoxication had the best prognosis, with a survival rate of 98.7% in this study.

Unilateral Subconjunctival and Retrobulbar Hemorrhage Secondary to Brodifacoum Toxicity in a Dog

An 8-year-old spayed female mixed-breed dog was presented for an acute onset of bleeding around the left eye. Mild exophthalmos and massive subconjunctival hemorrhage on the globe and nictitating membrane were present in the left eye. Retrobulbar hemorrhage was suspected, and pain was implied on opening of the mouth because the patient resisted and vocalized. No other abnormalities were found on ophthalmic or physical examination. Further questioning of the owner confirmed potential brodifacoum ingestion, and prothrombin time and partial thromboplastin time were both markedly elevated. Treatment with oral vitamin K1was implemented, and the subconjunctival hemorrhage was significantly improved within a few days of instituting treatment. All clinical signs of coagulopathy were completely resolved within 4 weeks of presentation. Coagulopathy secondary to brodifacoum ingestion can manifest as severe unilateral bulbar and nictitating membrane subconjunctival hemorrhage and exophthalmos due to retrobulbar hemorrhage without other clinical signs.

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.

Haemorrhage in seven cats with suspected anticoagulant rodenticide intoxication

Clinical features were evaluated in seven adult cats (six males, one female) with haemorrhage and presumptive anticoagulant rodenticide intoxication. Haemorrhage appeared as thoracic haemorrhage, otic bleeding, haematoma, melena, haematochezia, and petechiation. The most common other presenting signs were lethargy, anorexia, and tachypnoea or dyspnoea. Six cats were anaemic, four cats were mildly thrombocytopenic (58000-161000/ microL), and three had slightly decreased plasma protein or albumin values. The prothrombin time (30.3->100 s, reference range: 16.5-27.5 s) and activated partial thromboplastin time values (32.6->100 s; reference range: 14-25 s) were markedly prolonged in all cats. All cats received vitamin K(1)subcutaneously or orally (3.7-5 mg/kg body weight initially) and depending on severity of signs five cats were transfused with fresh whole blood. Plasma coagulation times improved in all cats and returned to normal in 1-5 days. Rodenticide poisons represent an important but relatively rare cause of haemorrhage in cats and can be effectively treated.

Brodifacoum toxicosis in two neonatal puppies

Eight out of a litter of 13 puppies were either born dead or died within 48 hours of birth. Three puppies that died shortly after birth were necropsied. Two puppies had hemorrhage in the thoracic and peritoneal cavities, intestinal serosa, and meninges. The third puppy was smaller than the other two puppies but did not have detectable hemorrhage. Brodifacoum, a second-generation coumarin anticoagulant, was detected in livers from the two puppies with hemorrhage. The dam did not have clinical signs of coagulopathy before or subsequent to whelping. The owners were confident that the dog had not been exposed to rodenticide for at least 4 weeks before whelping. A presumptive diagnosis of in utero brodifacoum toxicity was made. To the authors' knowledge this is the first time a second-generation coumarin anticoagulant has been detected in the liver of a newborn animal. This case is also unique because the dam was unaffected, suggesting that fetuses are more susceptible to brodifacoum toxicity than adult animals.

Rodenticides

Rodenticides are second only to insecticides in the prevalence of pesticide exposure. Hundreds of rodenticide products currently exist, yet only a handful of them are involved in most toxicoses of companion animals. The most commonly reported toxicoses in the United States are those caused by anticoagulant rodenticides, bromethalin, cholecalciferol, strychnine, and zinc phosphide. The pathophysiologic findings, diagnosis, and treatment of each of these five rodenticides are discussed.

Plasma superwarfarin levels and vitamin K1 treatment in dogs with anticoagulant rodenticide poisoning

The plasma concentration, plasma half-life (t1/2), and mean residence time (MRT) of rodenticide anticoagulants were determined in 21 dogs in which a preliminary diagnosis of anticoagulant rodenticide poisoning had been made. Brodifacoum, difethialone, and difenacoum were detected by high-performance liquid chromatography (HPLC) in the plasma of 13, 3, and 2 dogs, respectively. At presentation the plasma concentration ranged from below the detection limit (10 ng/L) to 851 ng/L. Toxin could not be detected in 3 dogs, despite these animals showing characteristic coagulation disturbances and a positive response to therapy with vitamin K1. In 7 dogs the estimated t1/2 of brodifacoum ranged from 0.9 to 4.7 (median 2.4) days with a MRT of 1.9 to 3.7 (median 2.8) days. In 2 dogs the individual t1/2 of difethialone was 2.2 and 3.2 days and the MRT was 2.3 and 2.8 days, respectively. Two dogs died during emergency treatment. Treatment in the remaining 19 dogs consisted of the administration of vitamin K1 and supportive therapy. The dose of vitamin K1 was reduced in a stepwise manner as long as the prothrombin time remained within physiological limits. The variation in initial plasma concentrations of the anticoagulants combined with the results of treatment support the idea that an individual therapeutic approach is warranted.

Evaluation of a prothrombin time optimized for the dog on plasmas with defined coagulation factor deficiency due to coumarin intoxication

The sensitivity of the standard prothrombin time (PT) was low when measured on 56 plasmas with a reduced activity of the coagulation factors mainly of the prothrombin complex (factors II, VII and/or X) taken from eight dogs at different times of vitamin K1 therapy after coumarin intoxication. This was demonstrable by use of three different Ca-thromboplastins. With the standard test only plasmas with an excessive decrease of coagulation factor activity (sum of activity decrease of the single factors in relation to the respective reference range [SAD] > 100%) were detectable with sufficient reliability. In contrast, by using a method optimized for dogs (1:20 sample predilution, fibrinogen substitution) and respecting the species specific features of coagulation physiology, pathological PT-values were measured in up to 70% of the samples (dependent on the Ca-thromboplastin) with slight reductions of single factor activity (SAD: 11-25%). Significant differences concerning the sensitivity were seen additionally between the different Ca-thromboplastins. Human placenta thromboplastin in particular, but also rabbit brain thromboplastin, were more sensitive than a preparation of recombinant human tissue factor. The correlation between the PT and the SAD was closer when using the optimized method (r = 0.919-0.954) compared to the standard test (r = 0.771-0.862). In contrast to the standard test, the PT optimized for dogs is, therefore, a reliable screening test to recognize a slight reduction in prothrombin complex. It is especially suitable for monitoring of vitamin K1 therapy after coumarin intoxication.