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.
Gastric impaction and obstruction of the small intestine associated with persimmon phytobezoar in a horse. Signs of mild colic, intermittent lethargy, and weight loss of 6 weeks' duration in a 2-year-old Quarter Horse gelding were attributed to persimmon (Diospyros virginiana) phytobezoar formation. Diagnosis of the phytobezoar was facilitated by gastric endoscopy. Signs of gastrointestinal tract obstruction were associated with a large phytobezoar in the lumen of the stomach, gastric ulceration, and obstruction of the small intestine (as a consequence of fragmentation of the primary bezoar). Conservative treatment, using mineral oil and dioctyl sodium sulfosuccinate, was unsuccessful. A celiotomy ...
[Hypocalcemia in a four-week-old foal]. Intake of Rumex, a plant genus of the Polygonaceae family, probably led through the assimilation of oxalic acid, to hypocalcaemia in a four-week old foal. This foal was presented with muscle rigidity and a stiff gait. Both the total and ionized calcium concentrations were low, 1.38 mmol/l and 0.54 mmol/l respectively. The foal was treated with a total of 150 ml of a 20% calcium solution IV. The foals neuromuscular signs resolved within a few hours after receiving calcium solution.
Black walnut induced laminitis. A 5-y-old Paint horse gelding was evaluated for acute laminitis after exposure to black walnut shavings. The gelding's feet were previously soaked in an ice bath continuously for approximately 24 h. Treatment consisted of anti-inflammatory and vasodilator therapy. Serial radiographs revealed progressive palmar deviation of the third phalanx and subsolar abscesses in both forefeet. The gelding developed purulent discharge from the right coronary band and the hoof wall detached circumfrentially. Euthanasia was elected after 54 days. Continual exposure of the gelding's feet to ice water temperatu...
[Accident report: animal nutrition in veterinary medicine–actual cases: houndstongue (Cynoglossum officinale) in pasture–a health hazard for horses]. Meteorism and colics were observed in horses after grazing on young pasture. The botanical analysis of a sample as taken by the owner revealed a great diversity of grasses, herbs and legumes. Houndstongue (Cynoglossum officinale) in its rosette stage was identified in amounts of 1% of the total sample, although this cannot be regarded as representative for the composition of the green fodder. This plant has been reported to be highly toxic for horses and other species, mainly during the early growth stadium due to its contents of pyrrolizidin alkaloids with a strong hepatotoxic activity. In th...
[Rhinopneumonia or mycotoxin intoxication? Neurologic phenomena in horses from a riding school]. In the course of several days most of the 40 riding-school horses turned out in paddocks developed ataxia of variable severity. Five of these horses showed severe ataxia and tremors, became paralyzed and were euthanized. Eleven privately-owned horses which were stabled on the same premises showed no clinical signs. The most likely diagnosis seemed to be the 'neurological form of EHV1', although the signs were not entirely typical. A few weeks later a second outbreak occurred among the riding-school horses and one of the privately-owned horses also showed signs of ataxia. In the meantime it had...
Mortality supposedly due to intoxication by pyrrolizidine alkaloids from Heliotropium indicum in a horse population in Costa Rica: a case report. This article describes a case of massive mortality among horses which was probably due to intoxication by pyrrolizidine alkaloids from Heliotropium indicum. Over 4 years more than 75% of a population of about 110 horses on a farm in Costa Rica died after showing nervous neurological symptoms. Two clinical manifestations were encountered, an acute and a chronic one, both with a fatal outcome. Pathological findings in 2 horses coincided with those reported in the literature for intoxication by pyrrolizidine alkaloids and were not specific for VEE. However Venezuelan equine encephalitis (VEE) was...
Use of phenytoin to treat digitalis-induced cardiac arrhythmias in a miniature Shetland pony. Two miniature Shetland ponies showing clinical signs of Digitalis purpurea (foxglove) poisoning were examined. One animal died shortly afterwards, but the second was treated successfully with the anti-arrhythmic agent, phenytoin, and was discharged after 16 days.
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...