Topic:Toxicology
Toxicology in horses involves the study of substances that can cause adverse effects when introduced to the equine body. This field examines the sources, mechanisms, and outcomes of exposure to toxic agents, which may include plants, chemicals, drugs, and environmental toxins. Understanding toxicology is essential for identifying and managing poisoning cases in horses. Research in this area often focuses on the identification of toxic compounds, their metabolic pathways, and the clinical symptoms associated with exposure. This page compiles peer-reviewed research studies and scholarly articles that explore the detection, effects, and management of toxic substances in equine health.
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 ...
Ivermectin: activity against larval Strongylus vulgaris and adult Trichostrongylus axei in experimental infections in ponies. Activity of ivermectin, administered IM at the dosage rate of 200 micrograms/kg of body weight, was evaluated in controlled tests against migrating larvae of Strongylus vulgaris and adult Trichostrongylus axei in experimental infections in 6 ponies raised worm-free. Ponies were given 2,190 or 2,400 infective 3rd-stage larvae of S vulgaris at 7 days before treatment and 22,000 or 22,750 infective 3rd-stage larvae of T axei at 42 or 45 days before treatment. Three ponies were given ivermectin plus vehicle, and 3 ponies were given the vehicle only; the ponies were euthanatized 7 or 9 days after t...
Acute vitamin D2 (ergocalciferol) toxicosis in horses: case report and experimental studies. Acute accidental vitamin D2 (ergocalciferol) toxicosis was diagnosed in a 6-month-old foal with extensive lesions of soft tissue mineralization. In an experimental study, three 18-month-old horses were given ergocalciferol per os at a rate of 9,300, 22,200, or 47,200 IU/kg of body weight/day for 21 days. Clinical signs or lesions were not seen in horses given the low and intermediate doses, whereas the horse receiving the highest dose developed clinical signs and lesions similar to those noted in the foal. Signs included depression, loss of appetite, weakness, limb stiffness with impaired mobi...
Gentamicin toxic nephropathy in horses with disseminated bacterial infection. Three clinical cases of toxic nephropathy in young horses were ascribed to gentamicin toxicity. Criteria for defining gentamicin-induced nephrotoxicosis were a serum urea nitrogen value greater than the pretreatment value or cylindruria, hematuria, and proteinuria in the absence of pyuria and bacteriuria. Recommended doses of gentamicin had been given in all cases. The nephropathy was reversible in 1 case in which the toxicosis was detected early and was treated by volume diuresis and drug withdrawal.
Environmental zinc and cadmium pollution associated with generalized osteochondrosis, osteoporosis, and nephrocalcinosis in horses. Several suspect causes of chronic zinc/cadmium toxicosis in horses near a zinc smelter were investigated following observations of lameness, swollen joints, and unthriftiness, particularly in foals. Two foals born and raised near the smelter were lame and had joint swellings that were attributable to severe generalized osteochondrosis. Zinc and cadmium concentrations were markedly increased in the pancreas, liver, and kidney. The serum of 1 foal, zinc and potassium concentrations were high, whereas calcium and magnesium concentrations were low. Marked nephrocalcinosis and osteoporosis were obs...
Renal cadmium and zinc concentrations in horses in Norway. Much of the recent interest in cadmium has been inspired by concern about the increasing levels of this element in the environment. Exposure to low levels of cadmium may cause chronic effects. The intake of cadmium takes place mostly via foods. Therefore it is of interest to determine the cadmium levels in domestic animals in order to evaluate possible hazards both to animals and man.
Effects of aflatoxins in young ponies. Sixteen clinically normal, healthy ponies were randomly assigned to 4 groups and given aflatoxin B1 in doses of 0.045, 0.030, 0.015, and 0 (control) mg/kg of body weight per day for 21 days (or total doses of 0.945, 0.630, 0.315, and 0 mg/kg). The animals were allowed to recover for 3 months and then were reassigned to 4 treatment groups such that each group during the 2nd trial included a pony from each of the groups of the 1st trial. The animals in the new groups were intubated and were given aflatoxin in doses of 0.4, 0.2, 0.1, and 0 (control) mg/kg/day for 5 days ( or total doses of 2.0, 1...
Effects of cytotoxic drugs on cultured equine cells in vitro. Sixteen cytotoxic drugs used in cancer chemotherapy in man were studied for cytopathic effect on equine fibrosarcoma, melanoma and normal equine lung cells in vitro. Three drugs, vincristine, melphalan and methotrexate, produced cytopathic effect
Phenylbutazone toxicosis in equidae: a biochemical and pathophysiological study. Toxic effects of phenylbutazone (PBZ) in ponies and horses were studied, using a variety of biochemical, pathophysiologic, and pathologic methods. At dosage levels of 10 to 12 mg/kg of body weight/day for 8 to 10 days, ponies frequently developed clinical signs of toxicosis characterized by hypoproteinemia. Studies using 51CrCl3 demonstrated that PBZ caused a protein-losing gastroenteropathy. The plasma loss was usually associated with gastrointestinal ulceration, but sometimes occurred without obvious lesions in mildly affected animals. Similar studies (8.2 mg/kg/day for 13 days) in Thoroughb...
Clinical toxicosis and erythrocyte cholinesterase inhibition of trichlorfon combined with mebendazole in horses. Thirty adult horses were used to compare the toxicity and cholinesterase (ChE) inhibition of various dosages of a combination anthelmintic, trichlorfon + mebendazole. Single oral doses of up to 5 times the effective dosage (39.7 mg of trichlorfon and 8.8 mg of mebendazole/kg of body weight) did not result in deaths. Horses given a placebo and horses treated at the recommended dosage rate showed few or no side effects, whereas horses given higher dosages showed dosage-related increases in the severity of clinical signs of organophosphate toxicosis. Dosage-related inhibition of erythrocyte ChE a...
A wire reclamation incinerator as a source of environmental contamination with tetrachlorodibenzo-p-dioxins and tetrachlorodibenzofurans. The authors investigated an outbreaks of unusual illnesses in humans and horses residing within 1.3 km of a wire reclamation incinerator. The study included site visits; medical and veterinary examinations; analyses of furnace ash, fly ash, soil, and biologic samples for air residues. Tetrachlorodibenzo-p-dioxins (TCDDs) and tetrachlorodibenzofurans (TCDFs) were discovered in furnace ash, fly ash, soil, horse fat, and horse liver samples.
Clinicopathological aspects of imidocarb dipropionate toxicity in horses. Six groups of four adult horses were twice injected intramuscularly at a 24 hour interval with 0, 2, 4, 8, 16 or 32 mg/kg of imidocarb dipropionate (IMDP) and monitored for 21 days. The LD50 of IMDP for 21 days after injection was two doses of 15.99 +/- 1.49 mg/kg with mortalities occurring within six days following the first injection. Increasing levels of IMDP were correlated with increasing rates of morbidity, mortality, local and systemic reactions, increasing levels of blood urea nitrogen, serum aspartate amino transferase, serum sorbitol dehydrogenase, serum creatine phosphokinase, neutr...
A comparative study of the toxicity of Fusarium verticillioides (= F. moniliforme) to horses, primates, pigs, sheep and rats. An isolate of Fusarium verticillioides (MRC826) that induced experimental leukoencephalomalacia, also caused acute toxicity when fed to pigs and administered per rumen fistula to sheep. Pigs developed severe pulmonary oedema while sheep manifested severe nephrosis and hepatosis. A less toxic isolate (F. verticillioides MRC602), fed to baboons, resulted in acute congestive heart failure or hepatic cirrhosis, depending on the dose. Both isolates were toxic to rats and caused similar lesions, namely, hepatic cirrhosis and intraventricular cardiac thrombosis.
Delayed monensin sodium toxicity in horses. Thirty-two horses were examined with a history of poor performance and unthriftiness several months after the ingestion of feed containing monensin sodium. Cardiac abnormality was diagnosed in 8 cases and suspected in 4 others. Necropsy examinations were performed on 6 cases with marked clinical symptoms and evidence of circulatory failure was found. Marked cardiac myopathy and fibrosis was a consistent feature. It is concluded that ingestion of monensin sodium by horses may cause either acute death or delayed cardiac circulatory failure as a result of specific cardiac myodegeneration.
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...
The value of zinc protoporphyrin in equine lead poisoning: a case report. A diagnosis of lead poisoning in a foal was established based on clinical signs and the presence of an elevation in the concentration of blood lead (40 microgram/dl). Additionally, ZPP was determined in whole blood and found to be significantly elevated compared to 10 normal horses not exposed to lead (634 vs 73 microgram/dl). An elevation in ZPP in man has been found to be a sensitive biochemical indicator of lead toxicity even before overt clinical signs are present. This report suggests that ZPP may be a useful screening test for evaluating biological toxicity due to lead in horses and poss...
Ultrastructural observations in ponies after treatment with monensin. Ultrastructural studies were made of myocardium, diaphragm, appendicular muscle, liver, and kidney of 3 ponies acutely poisoned with a single oral dose of monensin (4 mg/kg of body weight). These ponies developed severe signs of toxicosis and were killed 28 to 72 hours after treatment. Severe mitochondrial damage (swelling) and lipoidosis in myocardial tissues were observed in 2 of the 3 ponies; similar, but less severe, changes were observed in the 3rd pony. The hepatocytes of the 3 ponies were characterized by increased amounts of smooth endoplasmic reticulum, large numbers of lipid droplets...
Carcinogenicity of dichlorvos. Dichlorvos, 2,2-dichlorovinyl dimethyl phosphate, an organophosphate insecticide, is widely used for the control of agricultural, industrial, and domestic pests (Fig. 1) [1]. Dichlorvos is administered orally as an anthelmintic to swine, horses, cats, and dogs. It is applied by dermal application to cattle, goats, sheep, swine, and chickens to control fleas, flies, and mites. Cucumbers, radishes, lettuce, and tomatoes are treated with dichlorvos in greenhouses. Aerosols and strips are used for the control of ants, bedbugs, ticks, cockroaches, flies, mosquitoes, silverfish, spiders, and wasps. ...
Effects of copper pretreatment upon toxicity of selenium in ponies. Thirty-four adult ponies were used to determine the effects of single oral doses of copper (Cu) supplements (0, 20, and 40 mg of Cu/kg of body weight) on the toxicity of oral doses of selenium (Se) supplements (0, 2, 4, 6, and 8 mg of Se/kg of body weight) administered 24 hours after the copper was given. Signs of Se toxicosis-sweating, diarrhea, tachycardia, tachypnea, mild pyrexia, lethargy, and colic-developed in ponies given 6 and 8 mg of Se/kg of body weight without Cu pretreatment. Two of 4 ponies given 6 mg of Se/kg and both ponies given 8 mg of Se/kg without Cu pretreatment died within...
Evaluation of an analytical method for the diagnosis of cantharidin toxicosis due to ingestion of blister beetles (Epicauta lemniscata) by horses and sheep. An analytical method for cantharidin, using high performance liquid chromatography, was applied to field specimens from horses and sheep with blister beetle (Epicauta lemniscata) poisoning. Stomach content and urine proved to be valuable aids in diagnosis. One incident of cantharidin toxicosis in ruminants (sheep) was confirmed.