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.
Physiological, biochemical and haematological effects on horses of a phenylbutazone paste. Five matched pairs of horses were used to investigate the biochemical, haematological and general clinical effects of a new dosage schedule of a phenylbutazone paste administered under controlled feeding conditions. One group of horses received a loading dose (8.8 mg/kg) on day 1, followed by doses of 3.3 mg/kg daily on days 2 to 8, 10 and 12 with no treatment on days 9 and 11. The second group received equivalent doses of a placebo paste. Bodyweight, skin temperature, respiratory rate, glutamate dehydrogenase activity, packed cell volume, mean corpuscular volume and neutrophil count were alte...
The induction of equine laminitis with an aqueous extract of the heartwood of black walnut (Juglans nigra). An aqueous extract of the heartwood of black walnut (Juglans nigra) was given via stomach tube to 10 horses. Eight developed Obel grade 3 or 4 laminitis within 12 hr. Limb edema and mild sedation were the only other clinical signs observed. One horse was euthanized due to severe signs. The other 7 recovered within 6 days. Gas chromatography/mass spectrometry of aqueous extracts of heartwood, bark and nuts of black walnut identified juglone in the bark and nuts, but not in the heartwood. It was concluded that the aqueous extract of heartwood is laminogenic to horses, but the active ingredient i...
Effect of povidone-iodine on in vitro locomotion of equine neutrophils. Incubation of equine neutrophils with povidone-iodine solutions of greater than or equal to 0.2 per cent resulted in total inhibition of migration under agarose. This was caused by the cytotoxic effects of the solutions as shown by pyknosis and cell lysis. Lower concentrations of povidone-iodine, however, did not adversely affect neutrophil viability or locomotion.
Characterization of experimentally induced equine leukoencephalomalacia (ELEM) in ponies (Equus caballus): preliminary report. An isolate of Fusarium moniliforme (M-1225 Cairo #1) was cultured on autoclaved corn and fed daily to 5 ponies at a rate of 2.5 g corn/kg body wt. One pony developed clinical signs of toxicity after 28 days and was sacrificed. The remaining 4 ponies developed no clinical sign of toxicity even after extended exposure. Hematology, serum chemistry, cerebrospinal fluid (CSF), and liver and brain pathology were evaluated as possible diagnostic and prognostic indicators. Hematology was not informative. Aspartate aminotransferase and gamma-glutamyltranspeptidase activities were elevated only in the c...
[The clinical pharmacology of glycerol guaiacolate ether in the horse–a review]. The physical and chemical properties, administration, biotransformation, pharmacological effects, clinical applications, side-effects, toxicity and contraindications of glyceryl guaiacolate ether in the horse are reviewed.
A retrospective study of proliferative interstitial lung disease of horses in Florida. Proliferative and fibrosing interstitial lung disease was diagnosed in 20 horses submitted for necropsy between 1982 and 1985. Most of the horses were foals ranging from 3 days to 6 months in age. Six adult horses were affected. The macroscopic and microscopic characteristics of the lesions consisted of proliferative interstitial pneumonia and were similar to those of atypical interstitial pneumonia of ruminants. Based on morphologic features of the lesions, a toxic etiology is suspected for the induction of this naturally acquired primary equine lung disorder, but could not be specifically di...
The effects of natural exposure to high levels of zinc and cadmium in the immature pony as a function of age. To study the effects of environmental exposure to zinc and cadmium in immature foals, five pregnant ponies were raised within 2.9 km of the New Jersey Zinc Smelter in Palmerton, Pennsylvania. The mares and their foals were kept outdoors on timothy hay and orchard grass. The foals were examined daily for signs of illness and blood samples were taken monthly for estimation of serum zinc, copper, and ceruloplasmin levels. The foals were sacrificed at 2.5, 4.5, 8.5, 13.5, and 18.5 months of age. Necropsy revealed generalized osteochondrosis in joints of the limbs and cervical vertebrae, lymphoid h...
[Flunixin and its use in horses]. Flunixin is a non-steroidal anti-inflammatory agent, with a potent analgesic activity and a slight toxicity. It is largely used in horses, in the form of meglumine salt, for the treatment of inflammatory diseases or colics, and often identified in dopage cases. Physical and chemical properties of the drug, its pharmacological and toxicological properties, and its use in equine species are depicted.
Renal toxicity of non-steroidal anti-inflammatory drugs. Non-steroidal anti-inflammatory drugs represent the most heavily prescribed and used class of drugs in human medicine. Most are derivatives of either salicylates, propionic acid, indoleacetic acid, anthranilic acid, pyrazolone, or oxicams. They depress the synthesis of prostaglandins from arachidonic acid by reversible inhibition of the enzyme cyclooxygenase. In the kidney, prostaglandins PGE2 and PGI2 modulate the vasoconstrictor effects of angiotensin II, norepinephrine, and vasopressin. In the presence of volume contraction, anesthesia, or disease states associated with high levels of these...
Dimethyl sulfoxide (DMSO): a review. Dimethyl sulfoxide (DMSO) is a very simple compound that has stimulated much controversy in the scientific and popular literature. Fig. 1 It is an aprotic solvent. Therapeutic and toxic agents that are not soluble in water are often soluble in DMSO. DMSO has a very strong affinity for water; on exposure to air, pure DMSO is rapidly diluted. DMSO's physiologic and pharmacologic properties and effects are incompletely understood. Properties that are considered to be particularly important to its therapeutic and toxic effects include: its own rapid penetration and enhanced penetration of other su...
Dietary exposure to cadmium and health effects: impact of environmental changes. Cadmium exposure, metabolism, and effects are described especially in relation to dietary intakes. Data on dietary intakes in several countries have been complied from studies using the duplicate diet method or fecal analysis. These two methods seem to give more accurate data than estimates based on cadmium concentrations in food classes and food consumption (composite method). The present data on absorption and retention of ingested cadmium indicate that normally less than 5% is ingested, but absorption may increase in women who have iron deficiency. Earlier estimates of the critical concentr...
Some dynamic and toxic effects of theophylline in horses. A single intravenous administration of theophylline as aminophylline at 10 mg/kg to four mares induced a diuresis in which maximal urine production was more than seven times the control volume. The diuretic effect was maximal within the first hour post-administration, and lasted approximately 6 h. Theophylline resulted in dose-related tachycardia, polypnoea and nervous symptoms (tactile, visual and auditory hypersensitivity, muscle tremor, sweating) in normal mares, but had only minor effects on arterial and central venous blood pressures, intrapleural pressure, red blood cell variables and pl...
Experimentally induced phenylbutazone toxicosis in ponies: description of the syndrome and its prevention with synthetic prostaglandin E2. Phenylbutazone (PBZ) toxicosis was induced in 9 ponies to further define the clinical and pathologic changes occurring with this syndrome. Six additional ponies were treated with PBZ and a synthetic prostaglandin E2 to determine the role of prostaglandins in the pathogenesis of PBZ toxicosis. Ponies given only PBZ exhibited CNS depression, anorexia, weight loss, diarrhea, cyanotic mucous membranes, and oral ulcers. Total serum protein concentration gradually decreased during the 10-day treatment period. Marked mucosal atrophy, focal erosions, and ulcers characterized the lesions in the aliment...
Reserpine toxicosis in a horse. A single injection of reserpine in an adult horse was believed to induce toxicosis for several days. Clinical signs included erratic, colic-like behavior followed by depression, bradycardia, miosis, ptosis, and paraphimosis. Diarrhea was not observed and may have been due to the effect of xylazine given with the reserpine. The horse was supported with IV fluids and intensive nursing care. Gradual improvement was noted 72 hours after the horse received the drug. Qualitative analysis via high-performance liquid chromatography was positive for reserpine. Methamphetamine is the recommended antidot...
Unusual compound of small molecular weight in the serum of horses with acute grass sickness. An unusual compound of small molecular weight has been detected in serum from horses with acute grass sickness by solvent extractions and thin-layer chromatography. The substance has not been detected in the serum of normal horses or cases of equine colic and apparently disappears from grass sickness serum after two to three days of clinical illness. Although this compound is found in sera which are known to possess in vivo neurotoxicity, this property could not be demonstrated in either the total chloroform extract which contains the compound or in the hydrophilic serum components remaining a...
Bilateral laryngeal paralysis in the horse. Four two-year-old Thoroughbreds suffered an acute gastrointestinal illness shortly after dosing with mineral oil which was thought to have been contaminated with an organophosphate compound. Three weeks later all four were noted to be dyspnoeic and endoscopic examination showed that they had developed bilateral laryngeal paralysis. Two of the horses died during severe bouts of dyspnoea six and eight months later and the third was killed shortly thereafter. Examination of the left and right recurrent laryngeal nerves from these horses showed a severe loss of myelinated fibres distally, especial...
Clinical pharmacology and therapeutic uses of non-steroidal anti-inflammatory drugs in the horse. Weak organic acids possessing anti-inflammatory, analgesic and antipyretic properties--commonly known as aspirin-like drugs--have been used in equine medicine for almost 100 years. These non-steroidal anti-inflammatory drugs (NSAIDs) may be classified chemically into two groups; the enolic acids such as phenylbutazone and carboxylic acids like flunixin, meclofenamate and naproxen. All NSAIDs have similar and possibly identical modes of action accounting for both their therapeutic and their toxic effects. They block some part of the cyclo-oxygenase enzyme pathway and thereby suppress the synthe...
Experimental cantharidiasis in the horse. Crystalline cantharidin in an alfalfa cake or in aqueous suspension was given to 8 horses at a dosage level of 450 to 489 micrograms/kg of body weight (group 1) and 2 horses at a dosage level of 720 micrograms/kg (group 2) via nasogastric tube. Both group 2 horses and 1 group 1 horse died. Horses were evaluated at 6-hour intervals for 36 hours and then again at postcantharidin hours 48. Data evaluation consisted of a comparison of the nonsurvival and survival data to one another and their respective base-line values at each sampling period, irrespective of the route of administration and dosag...
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.