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Topic:Toxic plants
Toxic plants are a concern in equine management as they pose health risks to horses when ingested. These plants contain various compounds that can lead to adverse effects ranging from mild discomfort to severe illness or death. Horses may encounter toxic plants in pastures, hay, or during foraging. Common toxic plants include ragwort, yew, and oleander, each containing specific toxins that affect equine physiology differently. Understanding the identification, distribution, and toxicological impact of these plants is important for prevention and management. This page compiles peer-reviewed research studies and scholarly articles that explore the identification, toxic mechanisms, and management strategies of toxic plants in relation to equine health.
Hepatotoxicity associated with pyrrolizidine alkaloid (Crotalaria spp) ingestion in a horse on Easter Island. Since 1984, a significant number of privately owned and feral horses on Easter Island have died of a syndrome consisting of progressive anorexia, weight loss, obtundation, and other central nervous system abnormalities. A single horse experiencing clinical signs of the reported syndrome was identified, examined and necropsied. Clinical signs included inappetence, emaciation, ataxia and icterus. Gross necropsy findings included hepatic enlargement and mottling, ascites and gastric impaction. Histopathological lesions included hepatic hemorrhage and necrosis, periportal megalocytosis, portal fib...
Datura seed intoxication in two horses. A sunflower-based feed supplement grossly contaminated with the seed of a Datura sp. resulted in severe signs of poisoning in 2 horses. One horse died peracutely of acute gastric dilatation and rupture following ingestion of the contaminated feed. The 2nd horse developed unresponsive paralytic ileus that led to euthanasia. Examination of the feed and gastrointestinal contents of both horses showed a high proportion of the characteristic Datura sp. seeds. The clinical signs and pathology in both cases were consistent with intoxication by the parasympatholytic alkaloid components of Datura sp.
[Poisoning of horses by the bark of the false acacia (Robinia pseudoacacia)]. The present study describes the poisoning due to Robinia pseudoacacia in two horses. One of the horses showed mainly intestinal symptoms such as decreased intestinal motility and obstipation of the pelvic flexure. In the second animal central nervous symptoms were predominant. It showed intermittent phases of somnolence alternating with phases of excitation and head pressing. In addition mydriasis and a lacking menace response could be observed. Sensation to the head and the spinal reflexes were reduced. Symptomatic treatment was initiated in both animals and recovery occurred within 2 days.
A screening test for subclinical liver disease in horses affected by pyrrolizidine alkaloid toxicosis. To evaluate various biochemical tests as indicators of subclinical liver disease in horses exposed to pyrrolizidine alkaloid toxicosis. Methods: A clinical pathology field study. Methods: Twenty-two clinically normal horses from four properties in the Kimberley region of Western Australia. Methods: Serum samples from each horse were assayed for gamma glutamyltransferase, alkaline phosphatase and aspartate aminotransferase activities, and for serum bile acid concentration, albumin and total protein. Serum protein electrophoresis was performed and their amino acid profiles determined. Bromosulph...
An attempt to reproduce ‘mal seco’ in horses by feeding them Festuca argentina. 'Mal seco' is an almost invariably fatal disease of horses in Argentina and Chile, which resembles grass sickness, a dysautonomia of horses in Europe. The aetiology of mal seco remains unknown. An attempt to reproduce the disease was made by feeding horses with Festuca argentina, a plant considered to be toxic to animals and which was consistently found in the diet of nine horses suffering from mal seco. Three horses were fed with F argentina ad libitum for 28 days. The plant was infected with an endophytic fungus, whose morphological characteristics were in agreement with descriptions of Acre...
Diagnosis of oleander poisoning in livestock. Since mid-1989, 37 cases of oleander poisoning in livestock have been diagnosed at the California Veterinary Diagnostic Laboratory System. The most frequent source for oleander exposure was plant clippings. Sudden death was the most common presenting complaint. Other signs reported included diarrhea, pulmonary edema, tachycardia, cardiac arrhythmias, colic, and lethargy. In the past, a presumptive diagnosis of oleander poisoning could be based only on matching clinical signs with evidence of consumption of oleander. A new 2 dimensional Thin-layer chromatography analysis of ingesta for oleandri...
Pyrrole detection and the pathologic progression of Cynoglossum officinale (houndstongue) poisoning in horses. Houndstongue (Cynoglossum officinale), a noxious weed that contains pyrrolizidine alkaloids (PAs), infests pastures and fields in the western United States and Europe. The purpose of this study was to develop techniques to better diagnose PA poisoning and describe the progression of gross and microscopic lesions caused by houndstongue intoxication. Six horses were gavaged daily with a suspension of houndstongue containing 5 or 15 mg/kg total PA for 14 days. Two horses were treated similarly with ground alfalfa as controls. Liver biopsy samples and serum biochemical and hematologic values were ...
Toxicity of Palicourea marcgravii: combined effects of fluoroacetate, N-methyltyramine and 2-methyltetrahydro-beta-carboline. Feeding experiments carried out with cattle and horses could prove the toxic effects of P. marcgravii (Rubiaceae) in all cases. The typical symptoms of "sudden death", however, are observed in ruminants only. This difference could not be explained so far. Apart from fluoroacetate, two more substances also have influence the toxic effects and have been isolated from P. marcgravii for the first time: N-methyltyramine and 2-methyltetrahydro-beta-carboline (2-Me THBC). Structure elucidation of these compounds is mainly accomplished by 1H-NMR, 13C-NMR and MS techniques. Due to the small quantity of...
Recent acute and subacute mycotoxicoses recognized in France. Successful investigation and prevention of mycotoxic problems requires close collaboration between scientists from several disciplines ranging from agronomists and technologists required during production of food and feeds, to toxicologists and pathologists examining the effects of mycotoxins on animals and man. Zootoxic metabolites following fungal infection result from four general mechanisms: (i) secondary fungal metabolism (mycotoxins, eg, aflatoxins); (ii) bioconversion of vegetal compounds (eg, dicoumarol); (iii) plant reactions (phytoalexins, eg, coumestrol); and (iv) plant-fungus assoc...
[Ryegrass cramps in horses]. To elaborate the diagnosis of rye-grass intoxication in a stallion demonstrating a neurotoxic syndrome characterized by ataxia and incoordination, a number of diagnostic tests were performed. Results of both, blood chemistry and haematology gave no indication for organ-specific or systemic lesions. Chemical analysis of the hay fed to the horse revealed the presence of the mycotoxin lolitrem B in concentrations consistent with those described in sheep and cattle with similar symptoms. Thus, it was concluded that the animals demonstrated the rye-grass-stagger(RGS)-syndrome.
Outbreak of vesicular dermatitis among horses at a midwestern horse show. Dermatitis consisting of blisters on the nose and other parts of the body was reported among horses at a Midwestern horse show. Some horses also had jaundice, hematuria and anorexia. An outbreak investigation was initiated, and of 239 horses for which information could be obtained, 58 (24%) were found to have been affected. Median duration of illness was 5 days, and all horses recovered. Age, sex, water source, grain source, and stabling location were not associated with illness. The use of wood shavings bedding obtained at the show grounds was the factor most strongly associated with the deve...
Tropane alkaloids and toxicity of Convolvulus arvensis. Horses in a few, localized northern Colorado pastures exhibited weight loss and colic. At post mortem, intestinal fibrosis and vascular sclerosis of the small intestine was identified. The pastures where the affected horses grazed were overrun by field bindweed (Convolvulus arvensis). Bindweed from the pasture was found to contain the tropane alkaloids tropine, pseudotropine, and tropinone and the pyrrolidine alkaloids cuscohygrine and hygrine. Laboratory mice readily ate C. arvensis and exhibited a variety of abnormal clinical signs depending on the amount eaten. Similar alkaloids have been f...
Endogenous toxins and mycotoxins in forage grasses and their effects on livestock. Plant toxins are the chemical defenses of plants against herbivory. Grasses have relatively few intrinsic toxins, relying more on growth habit to survive defoliation and endophytic fungal toxins as chemical defenses. Forage grasses that contain intrinsic toxins include Phalaris spp. (tryptamine and carboline alkaloids), sorghums (cyanogenic glycosides), and tropical grasses containing oxalates and saponins. Toxic effects of these grasses include neurological damage (Phalaris staggers), hypoxia (sudangrass), saponin-induced photosensitization (Brachiaria and Panicum spp.), and bone demineraliza...
Isolation and identification of two potent neurotoxins, aspartic acid and glutamic acid, from yellow star thistle (Centaurea solstitialis). Horses grazing for prolonged periods on yellow star thistle (YST), a plant which grows wild in western parts of the United States, develop an extrapyramidal disorder known as nigropallidal encephalomalacia (NPE). Attempts have been made to identify, isolate, and characterize the toxins responsible for the disease in animals. Using the organotypic tissue culture system on mouse cortical explants as a specific assay method for neurotoxicological evaluation, it has been possible to isolate and characterize two potent neuroexcitotoxic compounds, aspartic and glutamic acids, the former being the ma...
Aggregate risk study of exposure to endophyte-infected (Acremonium coenophialum) tall fescue as a risk factor for laminitis in horses. Loline and ergot alkaloids found in endophyte-infected (Acremonium coenophialum) tall fescue (EITF) cause vasoconstriction of equine vessels in vitro. An aggregate risk study was used to evaluate the association between horses exposed to EITF and development of laminitis. Veterinary teaching hospitals participating in the Veterinary Medical Data Base were grouped by whether equine accessions were likely to have been at high, moderate, or low risk for exposure to EITF. From 1980-1990, there were 185,781 accessions, of which 5,536 had diagnosis of laminitis. Proportion of equine accessions with ...
Isolation of a compound from Eupatorium adenophorum (Spreng.) [Ageratina adenophora (Spreng.)] causing hepatotoxicity in mice. Regular ingestion of Eupatorium adenophorum [Ageratina adenophora (Spreng.)] or Crofton weed causes chronic pulmonary disease in horses mainly in Australia, New Zealand, and the Himalayas. The disease is characterized by pulmonary interstitial fibrosis, emphysema, alveolar epithelisation and reduced tolerance to exercise. Horses apparently are the only animals affected and there are numerous reports of farms losing all their horses. The disorder was produced experimentally in horse feeding trials, and it was shown that characteristic lesions occurred in the lungs. In studies with laboratory an...
Crotalaria juncea intoxication in horses. Twenty horses died 30 d after being fed a diet containing 40% of tritured Crotalaria juncea seeds. Before death, they had staggering, dyspnea and fever. At necropsy the most evident lesions were areas of lung parenchyma consolidation and enlarged and congested livers. Histopathological examination revealed diffuse fibrosing alveolitis with hyaline membranes, suggesting a blood-borne insult, and passive congestion in the liver with compression of the hepatocyte trabecules. To confirm the diagnosis, guinea pigs were given 60% of a commercial diet + 40% tritured C juncea seeds. After 4 mo of feed...
Torsion in quadrupeds and its impact on mammalian joints. Congenital and acquired torsion occur in the limbs of domestic animals. Congenital abnormalities are of clinical significance in foals; they are also seen in calves whose dams have ingested certain toxic plants that contain teratogenic agents. Acquired torsional deformities are most common in foals, but are also observed in adult horses, dogs, and llamas. Acquired rotational deformities are almost always associated with angular limb deformities. The clinical consequence of torsional deformities is the early development of degenerative joint disease.
An unusual manifestation of nettle rash in three horses. Three horses with an apparent neurological disorder resulting from nettle rash showed signs of ataxia, distress and muscle weakness, and two of them had urticaria. In each case the condition resolved within four hours, with no long term problems or recurrence.
Suspected red maple (Acer rubrum) toxicosis with abortion in two Percheron mares. Horses develop severe and often fatal hemolytic anemia after ingesting dried leaves from red maple (Acer rubrum) trees. Toxicosis appears related to an unknown oxidant present in the dried or wilted leaves. This case report describes 2 horses that aborted and developed fatal hemolytic anemia after consuming wilted leaves from red maple (Acer rubrum). While an absolute diagnosis was not confirmed due to lack of proper antemortem and postmortem examinations, red maple toxicosis appeared a reasonable diagnosis based on clinical signs and laboratory findings. Other differentials include equine inf...
Pyrrolizidine alkaloidosis in a two month old foal. A foal, small and jaundiced from birth, succumbed after two months to chronic hepatic damage which was characterised by fibrosis, biliary ductular hyperplasia and the presence of pleomorphic hepatocytes containing either a single large nucleus or multiple nuclei. The fixed liver contained sulfur-bound pyrroles, which are derived from pyrrolizidine alkaloids. During pregnancy the pasture was heavily infested with the pyrrolizidine alkaloid-containing plant, Senecio madagascariensis. The hepatic disease affecting the foal appears to have been initiated by consumption of the alkaloids by the mare...
Hoary alyssum (Berteroa incana) toxicity in a herd of broodmare horses. A herd of pregnant horses exposed to hoary alyssum through ingested hay developed acute and severe gastrointestinal toxicity accompanied by intravascular hemolysis. Postmortem lesions were consistent with these signs. Three horses had late-term abortions.
