Topic:Poisoning
Poisoning in horses refers to the ingestion, inhalation, or absorption of toxic substances that can adversely affect their health. These substances may include plants, chemicals, medications, or environmental toxins. Poisoning can lead to a range of clinical signs, from mild gastrointestinal upset to severe neurological or systemic effects, depending on the toxin involved. Common toxic substances for horses include certain plants like oleander and yew, heavy metals such as lead and arsenic, and specific pesticides or herbicides. This page compiles peer-reviewed research studies and scholarly articles that investigate the causes, effects, diagnosis, and management of poisoning in horses.
Cynoglossum officinale (hound’s-tongue)–a cause of pyrrolizidine alkaloid poisoning in horses. The death of 10 horses was attributed to feeding dried grass hay containing hound's-tongue, Cynoglossum officinale. Affected horses developed weight loss, icterus, photosensitization, and hepatic encephalopathy. Histologic examination of the liver of 3 of the horses revealed megalocytosis, biliary hyperplasia, and fibrosis characteristic of pyrrolizidine alkaloid poisoning. Hound's-tongue was found to contain large quantities (0.6% to 2.1%, dry matter basis) of toxic pyrrolizidine alkaloids, which, when fed to a pony for 20 days, caused liver fibrosis and biliary hyperplasia.
Illness in horses following spraying with amitraz. Sickness occurred in 3 of 4 horses within 24 h of being sprayed with an 0.025% w/v aqueous suspension of amitraz. The latter consisted of a portion of an amitraz aqueous suspension made up some 3 weeks previously, to which some freshly prepared spray fluid had been added. It seemed likely that the amitraz in the older solution had broken down to the highly toxic N-3, 5- dimethylphenyl N-methyl formamadine derivative and that this was in fact the main cause of the untoward effects observed. The horses displayed typical clinical signs of tranquillisation, depression, ataxia, muscular incoordinat...
Practical toxicologic diagnosis. Strychnine toxicosis is characterized by inducible tetanic seizures and metaldehyde poisoning by fine fasciculations progressing to generalized tremors and seizures. Intoxication with 1080 causes seizures, random running movements, vomiting, defecation, urination, acidosis and hyperglycemia. Intoxication with rodenticides causing coagulopathy is characterized by hemorrhage into body cavities but not necessarily external hemorrhage. Anticholinesterase insecticides cause salivation, urination and defecation, while chlorinated hydrocarbon insecticides cause CNS disturbances. Ethylene glycol intox...
Effect of monensin on the morphology of mitochondria in rodent and equine striated muscle. Heart, diaphragm, and rear limb muscle from ponies and rats treated with monensin were examined by light and electron microscopy. In both species, mitochondrial aberrations were observed in selected muscle cells. The aberrations consisted of loss of matrix substance (vacuolization) usually accompanied by swelling. Vacuolated mitochondria were characterized by an almost total loss of matrix substance with retention of the rudimentary cristae form. In ponies, most vacuolated mitochondria were observed in heart muscle though some also were found in the diaphragm. In rats, most vacuolated mitochon...
The toxicity of Datura stramonium (thorn apple) to horses. Meal contaminated by Datura stramonium seeds at the rate of 0.5% by weight was fed to two horses. Both horses showed clinical signs of depression, anorexia, weight loss, rapi heart and respiration rates, mydriasis, polyuria, polydipsia and diarrhoea. Both recovered with treatment. Maize screenings contaminated by the seeds had been used in the manufacture of the meal.
Outbreak of ragwort (Senecio jacobea) poisoning in horses. Five out of 20 horses (25 per cent) on one farm died from an acute hepatic encephalopathy typical of ragwort toxicosis. Circumstantial evidence implicated pasture rather than hay as the principal source of the toxic alkaloids. Plasma levels of gamma glutamyl transferase (GGT) were determined on three occasions in all surviving ragwort-exposed horses. Elevated GGT levels were a useful early indicator of hepatic damage although not all horses with this biochemical sign developed clinical disease.
Fatal acorn poisoning in a horse: pathologic findings and diagnostic considerations. Acorn poisoning was diagnosed in an 11-year-old Quarter Horse with signs of severe colic, tachycardia, hyperpnea, abdominal borborygmus, rectal tenesmus, and hemorrhagic diarrhea. The diagnosis was based on history and predisposing factors, clinical signs, laboratory data, acorn husks in the feces, the urinary gallic acid equivalent concentration, and necropsy findings. The most striking pathologic changes were gastrointestinal and mesenteric edema, ulcerative enterocolitis, and nephrosis.
Some effects of chronic mercuric chloride intoxication on renal function in a horse. Chronic mercuric chloride intoxication in an aged horse given 0.8 mg Hg/kg/day for 14 weeks was manifest by signs of progressive respiratory difficulty and renal disease. The effects were not self-limiting after mercury was withdrawn, and the animal was destroyed six weeks later. Renal function changes included heavy glycosuria, modest proteinuria, phosphaturia, reduced urine osmolality, gradually increasing urine production, reduced glomerular filtration rate, and terminally, azotemia. The condition bore similarities to the Fanconi syndrome in man. Urinary gamma-glutamyl transpeptidase, alkal...
Experimental lead toxicosis in ponies: comparison of the effects of smelter effluent-contaminated hay and lead acetate. Grass hay produced in the Coeur d'Alene River Basin of northern Idaho was fed to a group of 4 ponies. The hay contained Pb in concentration of 423 +/- 82 mg/kg and Cd in concentration of 10.8 +/- 1.4 mg/kg, resulting in daily exposures of the ponies to approximately 7.4 mg of Pb/kg and 0.19 mg of Cd/kg/day. The results in this group of ponies were compared with those from a group fed noncontaminated grass hay and given a daily dose of 10 mg of Pb/kg of body weight, in the form of lead acetate. Clinical toxicologic signs, hematologic changes, and blood and tissue Pb concentrations were similar ...
Hemolytic anemia in horses after the ingestion of red maple leaves. Signs of acute hemolytic anemia developed in 4 adult horses from 2 Georgia farms 3 to 4 days after the ingestion of wilted leaves from cut red maple trees (Acer rubrum). Clinical findings included weakness, polypnea, tachycardia, depression, icterus, cyanosis, and brownish discoloration of the blood and urine. Blood changes included methemoglobinemia, free plasma hemoglobin, decreased pcv, and Heinz bodies in erythrocytes. These findings plus hemoglobinuria suggested intravascular hemolysis. Three of the 4 horses diet 5 to 7 days after ingestion of the leaves. Gross pathologic changes included...
Toxicity of Cassia occidentalis in the horse. Three Shetland ponies were given a single oral dose of ground Cassia occidentalis seeds in aqueous suspension. The clinical signs observed resembled those seen in naturally occurring and experimental cases in cattle. The syndrome was characterized by an afebrile course, incoordination, recumbency and death. Elevations of blood alkaline phosphatase, CPK, LDH, and SGOT were observed. Although muscle lesions were not seen grossly, microscopic lesions included segmental necrosis of skeletal muscle fibers. The findings were regarded as sufficiently characteristic of C. occidentalis poisoning to be ...
Acute hemolytic anemia, methemoglobinemia, and heinz body formation associated with ingestion of red maple leaves by horses. From June 1975 through June 1979, acute hemolytic anemia developed in 11 horses from 7 New York farms. Of the 7 horses that died, 6 had methemoglobinemia. In the 4 horses that recovered, methemoglobinemia was not observed. but Heinz body formation was seen in 3 of the 4. On 2 of the premises involved, frank methemoglobinemia was observed concurrently with Heinz body formation, suggesting a relationship between the pathogenesis of methemoglobinemia and Heinz body formation in the hemolytic process. In addition to the 11 cases described, 22 clinically similar cases were reported to us during the...
Field outbreaks of leukoencephalomalacia in horses consuming maize infected by Fusarium verticillioides (= F. moniliforme) in South Africa. Four outbreaks of leukoencephalomalacia in horses in widely separated areas in South Africa are reported. The clinical signs and pathological lesions observed in each outbreak are briefly described. Mouldy home-grown maize from which Fusarium verticillioides (Sacc.) Nirenberg (= F. moniliforme Sheldon) was isolated in every instance, was involved in the outbreaks. Clinical signs and pathological lesions were identical to those seen in experimentally produced cases of F. verticillioides poisoning in horses.
Toxic effects of lasalocid in horses. Lasalocid was given to horses in a series of sequentially increasing single oral doses ranging between 5 and 30 mg/kg of body weight, with an appropriate washout period between treatments. One of the 5 horses died after a dosage of 15 mg/kg, 1 of 3 horses died after 21 mg/kg, 1 of 3 horses died after 22 mg/kg, and 1 of 2 horses died after 26 mg/kg. The LD50 of lasalocid for horses was estimated to be 21.5 mg/kg. Monensin was given to horses in a similar manner at dosages of 1, 2, and 3 mg/kg of body weight. One of the 2 horses died after a dosage of 2 mg/kg and 1 horse died after a dosage of 3...