Diagnosis of Taxus (Yew) Poisoning in a Horse

Diagnostic Pathology of Equine Toxicoses

This article is intended to highlight toxicosis-associated pathology in horses that might be observed by a clinician in the living animal and at gross necropsy. When the clinician is aware of these pathologic changes (particularly when coupled with a suggestive environmental or herd history), then collaboration with a diagnostic laboratory can begin to help identify specific toxicants. Proper sampling and communication with the diagnostic laboratory will vastly improve the likelihood of a specific diagnosis; postmortem sampling and specimen submission are reviewed in the last section of this article.

Toxic Garden and Landscaping Plants

Many popular ornamental shrubs are not only beautiful but also toxic when ingested in sufficient quantities. Common toxic landscaping shrubs in North America include yew (Taxus spp), oleander (Nerium oleander), and rhododendrons and azaleas (Rhododendron spp). Horses are often exposed when plant trimmings are placed within reach or discarded in pastures. Occasionally clippings or fallen leaves contaminate hay. Some plants are unpalatable unless dried and mixed with hay or lawn clippings but others are ingested more readily. In many cases, disease can be severe and treatment unrewarding; therefore, client education is critical to preventing serious and potentially fatal poisonings.

Poisonous Plants of the Indian Himalaya: An Overview

Indian Himalayan region (IHR) supports a wide diversity of plants and most of them are known for their medicinal value. Humankind has been using medicinal plants since the inception of civilization. Various types of bioactive compounds are found in plants, which are directly and indirectly beneficial for plants as well as humans. These bioactive compounds are highly useful and being used as a strong source of medicines, pharmaceuticals, agrochemicals, food additives, fragrances, and flavoring agents. Apart from this, several plant species contain some toxic compounds that affect the health of many forms of life as well as cause their death. These plants are known as poisonous plants, because of their toxicity to both humans and animals. Therefore, it is necessary to know in what quantity they should be taken so that it does not have a negative impact on health. Recent studies on poisonous plants have raised awareness among people who are at risk of plant toxicity in different parts of the world. The main aim of this review article is to explore the current knowledge about the poisonous plants of the Indian Himalayas along with the importance of these poisonous plants to treat different ailments. The findings of the present review will be helpful to different pharmaceutical industries, the scientific community and researchers around the world.

Pericardial Disease, Myocardial Disease, and Great Vessel Abnormalities in Horses

Pericardial, myocardial, and great vessel diseases are relatively rare in horses. The clinical signs are often nonspecific and vague, or related to the underlying cause. Physical examination usually reveals tachycardia, fever, venous distension or jugular pulsation, a weak or bounding arterial pulse, ventral edema, and abnormal cardiac auscultation such as arrhythmia, murmur, or muffled heart sounds. The prognosis depends on the underlying cause and the disease progression, and ranges from full recovery to poor prognosis for survival. This article focuses on the etiology, diagnosis, prognosis, and treatment of pericarditis, pericardial mass lesions, myocarditis, cardiomyopathy, and great vessel aneurysm or rupture.

Yew (Taxus) intoxication in free-ranging cervids

Wild ruminants, including deer species (cervids) have incorrectly been regarded as refractory to yew (Taxus) intoxication. This assumption has been based upon anecdotal observations of individual deer browsing on yew over time without apparent adverse effect. A single case of yew intoxication was reported in a free-ranging Norwegian moose (Alces alces) in 2008. The current report describes five additional cases of yew toxicosis in moose, seven in roe deer (Capreolus capreolus) and two in reindeer (Rangifer tarandus tarandus), all in Norway. The animals were found dead during the winter, close to or within gardens containing yew plants showing signs of browsing. Gross findings included lung congestion and edema, thoracic and pericardial effusion, bilateral heart dilatation, epi- and endocardial hemorrhage, and enlarged (congested) spleen. Yew plant remnants were detected in the rumen of all animals with the exception of a single moose. Histology revealed multifocal acute myocardial degeneration and necrosis with hemorrhage in roe deer, but not in the two other species. A qualitative high performance liquid chromatography-ion trap mass spectrometry analysis was used to tentatively identify five major Taxus alkaloids (taxines) in crude yew extracts and in heart and liver samples from the moose cases. All five major taxines were detected with good signal/noise ratio in tissue samples from the four moose with visible ruminal yew content, whereas lower levels of taxines were detected in the moose without visible ruminal yew content. Possible differences in interspecies tolerance to taxines and role of individual protective adaptation are discussed.

Diagnostic approach to catastrophic musculoskeletal injuries in racehorses

Catastrophic musculoskeletal injuries are the most common cause of euthanasia or spontaneous death in racehorses, and the most common cause of jockey falls with potential for serious human injury. Horses are predisposed to the vast majority of these injuries by preexisting lesions that can be prevented by early diagnosis and adequate bone injury management. A thorough examination of the musculoskeletal system in racehorses often determines the cause of these injuries and generates data to develop injury prevention strategies. We describe the diagnostic approach to musculoskeletal injury, review the methodology for the examination of racehorse limbs, and provide anatomy and pathology tools to perform an organized and thorough postmortem examination of the musculoskeletal system in equine athletes.

Poisonous or non-poisonous plants? DNA-based tools and applications for accurate identification

Plant exposures are among the most frequently reported cases to poison control centres worldwide. This is a growing condition due to recent societal trends oriented towards the consumption of wild plants as food, cosmetics, or medicine. At least three general causes of plant poisoning can be identified: plant misidentification, introduction of new plant-based supplements and medicines with no controls about their safety, and the lack of regulation for the trading of herbal and phytochemical products. Moreover, an efficient screening for the occurrence of plants poisonous to humans is also desirable at the different stages of the food supply chain: from the raw material to the final transformed product. A rapid diagnosis of intoxication cases is necessary in order to provide the most reliable treatment. However, a precise taxonomic characterization of the ingested species is often challenging. In this review, we provide an overview of the emerging DNA-based tools and technologies to address the issue of poisonous plant identification. Specifically, classic DNA barcoding and its applications using High Resolution Melting (Bar-HRM) ensure high universality and rapid response respectively, whereas High Throughput Sequencing techniques (HTS) provide a complete characterization of plant residues in complex matrices. The pros and cons of each approach have been evaluated with the final aim of proposing a general user's guide to molecular identification directed to different stakeholder categories interested in the diagnostics of poisonous plants.

Veterinary Forensic Toxicology

Veterinary pathologists working in diagnostic laboratories are sometimes presented with cases involving animal poisonings that become the object of criminal or civil litigation. Forensic veterinary toxicology cases can include cases involving animal cruelty (malicious poisoning), regulatory issues (eg, contamination of the food supply), insurance litigation, or poisoning of wildlife. An understanding of the appropriate approach to these types of cases, including proper sample collection, handling, and transport, is essential so that chain of custody rules are followed and proper samples are obtained for toxicological analysis. Consultation with veterinary toxicologists at the diagnostic laboratory that will be processing the samples before, during, and after the forensic necropsy can help to ensure that the analytical tests performed are appropriate for the circumstances and findings surrounding the individual case.

Alkaloid-Containing Plants Poisonous to Cattle and Horses in Europe

Alkaloids, nitrogen-containing secondary plant metabolites, are of major interest to veterinary toxicology because of their occurrence in plant species commonly involved in animal poisoning. Based on epidemiological data, the poisoning of cattle and horses by alkaloid-containing plants is a relatively common occurrence in Europe. Poisoning may occur when the plants contaminate hay or silage or when forage alternatives are unavailable. Cattle and horses are particularly at risk of poisoning by Colchicum autumnale (meadow saffron), Conium maculatum (poison hemlock), Datura stramonium (jimson weed), Equisetum palustre (marsh horsetail), Senecio spp. (ragwort and groundsel) and Taxus baccata (European yew). This review of poisonous alkaloid-containing plants describes the distribution of these plants, conditions under which poisoning occurs, active toxic principles involved and subsequent clinical signs observed.

Characterization of cardiac lesions in calves after ingestion of Japanese yew (Taxus cuspidata)

Plants of the genus Taxus are common ornamental shrubs that contain cardiotoxic alkaloids. Gross lesions consistent with heart failure are frequently reported in fatal cases; however, microscopic lesions in the heart have not been well characterized. The current report describes 2 related outbreaks in which 7 of 30, 250-kg calves died after confirmed exposure to clippings of Japanese yew (Taxus cuspidata). Three calves died 24 hr after initial exposure, with no significant gross or histologic lesions. Leaves of the yew plant were identified within the rumen contents, and Taxus alkaloids were confirmed by gas chromatography-mass spectrometry. Following the initial diagnosis, the yew clippings were burned. Two days later, the remaining calves were reintroduced to the enclosure. Within 24 hr, 3 additional calves began to show clinical signs of depression (3/3) or labored breathing (1/3), and by the fourth day, these 3 calves and an additional calf were found dead. Partially burnt yew leaves were found during close inspection of the enclosure. Two of 3 calves submitted for necropsy were severely autolyzed; the third had pulmonary edema and mild fibrinous pleural effusion. Histologic lesions in the latter included multifocal cardiac myocyte hypereosinophilia, sarcolemma fragmentation, pyknosis, karyolysis, myocyte loss, and a mild interstitial lymphoplasmacytic infiltrate with edema. Moderate fibrinosuppurative interstitial pneumonia was the only other significant finding. Cardiac changes were attributed to damage from the initial exposure to Taxus 6 days prior to death.

Plant poisoning in domestic animals: epidemiological data from an Italian survey (2000-2011)

An Italian epidemiological study based on the human Poison Control Centre of Milan (Centro Antiveleni di Milano (CAV)) data related to domestic animal poisoning by exposure to plants, was carried out in collaboration with the Veterinary Toxicology Section of the University of Milan. It encompasses a 12-year period, from the beginning of 2000 to the end of 2011. Calls related to toxic plants accounted for 5.7 per cent of total inquiries (2150) received by CAV. The dog was the most commonly poisoned species (61.8 per cent of calls) followed by the cat (26 per cent). Little information was recorded for other species. Most exposures (73.8 per cent) resulted in mild to moderate clinical signs. The outcome was reported in only 53.7 per cent of cases, and fatal poisoning accounted for 10.6 per cent of these cases. Glycoside, alkaloid, oxalate, toxalbumin, saponin, terpene and terpenoid-containing plants were recorded and found to be responsible for intoxication. Cycas revoluta, Euphorbia pulcherrima, Hydrangea macrophylla, Nerium oleander, Rhododendron species and Prunus species were the plants most frequently involved. Epidemiological data from this Italian survey provide useful information on animal exposure to plants and confirm the importance of plants as causative agents of animal poisoning.

Eight cases of fatal and non-fatal poisoning with Taxus baccata

This paper describes two fatalities, three non-fatal intentional and three accidental oral ingestions of yew (Taxus baccata) leaves. In all cases the post-mortem external examinations showed no signs of violence. Internal examinations revealed small green, needle-like particles on the tongue, in the esophagus and in the stomach. Yew leaves were also identified in the stomach contents, whereas Taxus leaves were cut into small pieces and then ingested in one case. The analytical method used was based on a liquid-liquid-extraction under alkaline conditions followed by LC-MS/MS analysis (QTRAP 5500). Chromatographic separation was achieved by HPLC on a Kinetex C18 2.6u (100×3) mm. The analytical method allows the simultaneous identification and quantification of the commercially available yew alkaloids taxoids (m/z): paclitaxel (854.2→105.0/286.1), 10-deacetyltaxol (10-DAT: 812.2→105.0/286.1), baccatin III (BAC III: 604.0→105.0/327.0), 10-deacetylbaccatin III (10-DAB III: 562.1→105.0/327.0), cephalomannine [taxol B] (562.1→105.0/327.0) and of 3,5-dimethoxyphenol (3,5-DMP: 155.0→111.9/122.9) also encompassing the qualitative analysis of the alkaloidal diterpenoids (Q1→194.0/107.0); reference mass spectra obtained from a yew leaves extract: monoacetyltaxine (MAT: 568.4), taxine B (584.2), monohydroxydiacetyltaxine (MHDAT: 626.4), triacetyltaxine (TAT: 652.4), monohydroxytriacetyltaxine (MHTAT: 668.4). In both fatalities, paclitaxel, 10-DAT and cephalomannine were not identified in urine, cardiac and femoral blood but all taxoids and 3,5-DMP were present in stomach content and excreted into the bile. In urine, highest 3,5-DMP concentration was 7500 μg/L and 23,000 μg/L after enzymatic hydrolysis, respectively. In intentional and accidental poisonings, when electrocardiogram (ECG) examinations revealed ventricular tachycardia and/or prolonged QRS intervals, taxines were identified in plasma/serum, even after the ingestion of a few number of yew leaves, when 3,5-dimethoxyphenol was not even found. According to the data from one near-fatal intentional poisoning, elimination half-life of MAT, TAXIN B, MHDAT and MHTAT in serum was calculated with 11-13 h and taxines were detected up to t=+122 h post-ingestion of approximately two handfuls of yew leaves.

Myocardial fibrosis associated with previous ingestion of yew (Taxus sp.) in a Holstein heifer

Twenty-six 5-month-old Holstein calves were accidentally exposed to discarded branches of yew bushes ( Taxus sp.). Several calves were found dead approximately 24 hr after exposure; however, a few calves died several days after exposure. One calf died 18 days after the initial exposure to Taxus sp. and was examined on the farm via necropsy. Gross lesions included ascites, and dilated and flaccid myocardial ventricles. Sections of formalin-fixed heart were submitted to the Indiana Animal Disease Diagnostic Laboratory for histopathologic examination; fresh rumen contents were submitted for toxicologic testing. Histologically, large areas of myocardium were replaced by fibrous connective tissue, suggesting previous myocardial necrosis. Taxus alkaloids were identified in the rumen contents using gas chromatography–mass spectrometry. Based on the clinical history, the gross and histologic lesions, the identification of Taxus alkaloids in the rumen contents, and lack of exposure to other known cardiotoxic agents, yew toxicity was considered the cause of death in this calf. Ingestion of taxines is known to cause acute and subacute toxicity in human beings and animals; however, a chronic clinical course and severe histologic lesions have not been previously associated with yew toxicity. Although only 1 calf was examined, this case suggests that yew toxicity can result in a prolonged clinical course in cattle and can cause histologic myocardial lesions.

Fatal poisoning with Taxus baccata: quantification of paclitaxel (taxol A), 10-deacetyltaxol, baccatin III, 10-deacetylbaccatin III, cephalomannine (taxol B), and 3,5-dimethoxyphenol in body fluids by liquid chromatography-tandem mass spectrometry

This method development was to confirm the fatal ingestion of toxic yew plant material in postmortem samples (stomach content, urine, femoral blood, cardiac blood, bile, and brain tissue) collected from a 22-year-old man who committed suicide by ingesting yew leaves. The analytical method was based on a liquid-liquid extraction under alkaline conditions followed by LC-MS-MS analysis. Chromatographic separation was achieved by HPLC on a Kinetex C18 2.6u (100 × 3 mm) coupled to a QTRAP 5500 system. The method allows the simultaneous identification and quantification of the yew alkaloids taxoids paclitaxel (taxol A), 10-deacetyltaxol, baccatin III, 10-deacetylbaccatin III, cephalomannine (taxol B), and 3,5-dimethoxyphenol; the alkaloidal diterpenoids monoacetyltaxine, taxine B, monohydroxydiacetyltaxine, triacetyltaxine, and monohydroxytriacetyltaxine were also identified. The initial hypothesis of yew tree (Taxus baccata) poisoning was confirmed. The quantitative evaluation revealed taxoid concentrations ranging from 4.5 to 132 µg/L (stomach content), 1 to 200 µg/L (urine), <0.5 to 12 µg/L (cardiac blood), <0.5 to 7.3 µg/L (femoral blood), and 4.9 to 290 µg/L (bile). In brain tissue, none of these taxoids could be detected (<0.5 µg/L). In urine, after enzymatic hydrolysis, the concentration of 3,5-dimethoxyphenol (3,5-DMP) was 23,000 µg/L. The alkaloidal diterpenoids were found in all postmortem samples. The newly developed LC-MS-MS method enables the identification of alkaloidal and non-alkaloidal diterpenoids and 3,5-dimethoxyphenol in human body fluids and tissues for the confirmation of accidental or intentional poisonings with yew plant material.

Monitoring of aglycons of yew glycosides (3,5-dimethoxyphenol, myrtenol and 1-octen-3-ol) as first indicator of yew presence

The toxicity of yew (Taxus spp) is well known from ancient times and is mainly due to taxins acting as inhibitors of calcium and sodium transport across the cell membrane of cardiac myocytes. The confirmation of yew taxins in body fluids can be carried out by liquid chromatography-tandem mass spectrometry (LC-MS/MS). However, before selecting this precise but expensive technique, an orientation test should be done to ascertain yew presence as toxic agent in the organism. As the 3,5-dimethoxyphenol (3,5-DMP), myrtenol and 1-octen-3-ol appear as glycosidically bound volatile compounds and are very yew specific, the detection of 3,5-DMP and the measurement of 1-octen-3-ol / myrtenol concentration ratio constitute reliable indicators of yew presence in forensic cases. The detection of these compounds is easily performed by gas chromatography-mass spectrometry (GC-MS) (SIM) after an enzymatic hydrolysis (β-glucosidase) allowing the release of volatile compounds from yew glycosides.

Degradation of yew, ragwort and rhododendron toxins during composting

Recent concerns have been raised that plants such as ragwort (Senecio jacobaea), yew (Taxus baccata) and rhododendron (Rhododendron ponticum) that are toxic to livestock may be included in compost windrows but may not be fully detoxified by the composting process. This study investigates the decomposition during composting of toxic pyrrolizidine alkaloids present in ragwort, taxines (A and B) present in yew, and grayanotoxins (GTX I, II, and III) present in rhododendron during composting. Plant samples were contained within microporous bags either towards the edge or within the centre of a pilot-scale compost heap. They were destructively harvested at regular intervals over 1200 degrees C cumulative temperature (about three months). Samples were analysed for levels of toxins by liquid chromatography time of flight mass spectrometry (LC-TOF-MS). Pyrrolizidine alkaloids and taxines were shown to degrade completely during the composting process. While GTX I showed significant reductions, concentrations of GTX III remained unchanged after 1200 degrees C cumulative temperature. However, estimates of exposure to grazing livestock coming into contact with source-segregated green waste compost containing up to 7% rhododendron suggest that GTX III poses no appreciable risk.

Taxus sp. intoxication in three Francois' langurs (Trachypithecus francoisi)

Three Francois' langurs (Trachypithecus francoisi) were found dead, without previous clinical signs, over a 48-hour period at a zoological institution after transfer to a new exhibit. A hybrid yew shrub (Taxus baccata X T. cuspidata) was found in close proximity to the exhibit perimeter fence. Despite clinical suspicion of yew intoxication, thin-layer chromatography performed on gastric contents was negative. However, microscopic examination of gastric contents revealed multiple yew fragments, and taxine alkaloids were detected by gas chromatography and mass spectrometry of the gastric contents to confirm yew intoxication. Acute death of the animals prevented treatment. The fourth langur in the collection survived, most likely because of its low rank in the troop's hierarchy, with a suspected small amount or none of the plant ingested. To the authors' knowledge, this case report is the first yew intoxication documented in a nonhuman primate species. Taxus spp. intoxication is an often fatal condition reported in domestic animals and humans. In comparison with these species, mortality appeared delayed in the Francois' langurs, most likely because of their unique gastrointestinal anatomy, with both foregut and colonic fermentation. Plant intoxication should be a differential diagnosis when multiple acute deaths are observed after recent introduction to a new enclosure.

A comparative study of five fatal cases of Taxus poisoning

The study presents five fatal cases of poisoning with Taxus spp., all of which were suicides of young people aged between 16 and 26 years. Yew leaves were consumed in four fatalities, whereas a mash from Taxus was ingested in one case. No relevant concentrations of alcohol, narcotic drugs, and pharmaceuticals were determined in postmortem toxicological screening. At forensic autopsy, a widely dilated pupil was found in two decedents. Furthermore, autopsy showed unspecific findings of intoxication in all cases: acute blood congestion of lungs, liver, kidney, and brain as well as dilated cardiac ventricles. No signs of violence could be found in any of the fatalities. Yew leaves were identified in four cases in the stomach and duodenum. 3,5-Dimethoxyphenol, the aglycon of the Taxus ingredient taxicatine, was determined as toxicological evidence for the absorption of yew ingredients. Taxus intoxication could be confirmed by 3,5-dimethoxyphenol concentrations in cardiac blood between 31 and 528 ng/ml for all cases. 3,5-Dimethoxyphenol was also detected in stomach contents as well as in urine, liver, kidneys, and brain samples. Based on the different concentrations of 3,5-dimethoxyphenol determined in the cardiac blood samples, it was concluded that the form of ingestion plays a decisive role in the process of poisoning. Finally, a toxic range for Taxus poisoning based on 3,5-dimethoxyphenol as marker substance is proposed as orientation.

Quantitative determination of taxine B in body fluids by LC–MS–MS

A new specific and sensitive LC-MS-MS method for the detection of taxine B and isotaxine B, the main toxic pseudo-alkaloids from yew (Taxus sp.), in biological samples (blood, urine, gastric content) was developed. Biological samples were prepared for LC-MS-MS by means of solid-phase extraction (SPE) procedure and yielded a recovery of 86%. Chromatographic separation was achieved using an RP(18) column. Detection of taxine B and isotaxine B was performed using multiple reaction monitoring with m/z 584.2 as precursor ion, i.e. [M+H](+), of both isomers and m/z 194.3 and m/z 107.1 as product ions after collision-induced dissociation. Docetaxel was applied as internal standard. The method was fully validated for the analysis of blood samples. Linearity was proven in the range from 0.1-500 ng/g. The limit of detection and the limit of quantitation are 0.4 and 2 ng/g, respectively. The method was applied to the determination of taxine B and isotaxine B in four fatal cases (two humans, two horses) with suspected yew intoxication. Blood levels were 105, 168, 174 and 212 ng/g.