Toxins in horses refer to a variety of substances that can cause adverse health effects when ingested, inhaled, or absorbed through the skin. These substances can originate from plants, chemicals, feed contaminants, or environmental sources. Common toxins affecting horses include mycotoxins, heavy metals, and certain plants like ragwort and oleander. Exposure to these toxins can lead to a range of clinical symptoms, from mild discomfort to severe illness or death. Research in this area focuses on identifying toxic agents, understanding their mechanisms of action, and developing strategies for prevention and treatment. This page compiles peer-reviewed research studies and scholarly articles that explore the sources, effects, and management of toxins in equine health.
Aller WW, Edds GT, Asquith RL.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...
Pienaar JG, Kellerman TS, Marasas WF.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.
Al-Khalidi NW, Weisbrode SE, Dubey JP.Nine ponies were fed 100,000 infective Toxoplasma gondii oocysts and were given corticosteroid injections before and after feeding the T gondii oocysts. Titers to the Sabin-Feldman dye tests (1:2 to 1:16,384) developed within postinoculation days (PID) 7 to 21 and antibodies persisted to PID 133. Toxoplasma organisms were isolated from the tissues of 4 ponies (heart of 4, brain of 2, spinal cord of 3, diaphragm of 1, skeletal muscle of 1, liver of 1, kidneys of 1) killed between PID 36 and 63, but not from 5 ponies killed between PID 117 and 150. Seemingly, ponies are one of the more resistant...
McDonald GK.A six year old Percheron mare was presented with a history of spontaneous unilateral epistaxis of 24 hours duration. The blood one stage prothrombin and partial thromboplastin times were markedly prolonged. A diagnosis of moldy sweetclover poisoning was made on the basis of the history and clinical and laboratory findings. A single whole blood transfusion and four daily intravenous injections of vitamin K(3) proved to be a successful treatment.
Ray AC, Post LO, Hurst JM, Edwards WC, Reagor JC.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.
True RG, Lowe JE.Juglone, a toxic compound found in all parts of plants of the walnut tree family Jugans, was evaluated as the possible toxin involved in black walnut shaving-associated laminitis in the horse. Large amounts (up to 1 g) of this chemical administered per os inconsistently caused mild signs of laminitis in ponies. Topical application of juglone to the digits of horses caused local skin irritation but did not cause laminitis. Intravenous administration of juglone caused acute pulmonary edema in some individuals previously exposed to the compound per os or IV.
Swerczek TW.Four experiments were performed to elucidate the pathogenesis of toxicoinfectious botulism in horses and foals. Groups of horses and foals were inoculated with one of the following: (1) crude toxin of Clostridium botulinum, type B, given IV, (2) C botulinum spores, given IM, (3) C botulinum spores, given IM, in necrotic lesions, and (4) C botulinum spores, given orally with and without dexamethasone. Toxin of C botulinum in minute amounts is toxic to horses. Clostridium botulinum spores produced toxicosis only when necrotic lesions were present. When C botulinum spores were given orally, they ...
Haliburton JC, Vesonder RF, Lock TF, Buck WB.Signs and lesions characteristic of equine leucoencephalomalacia were produced in one of two donkeys given corn cultured with Fusarium moniliforme Sheldon. Gross and histopathologic lesions of the cerebrum included an extensive necrotic cavitation within one cerebral hemisphere, disruption and rarefication of the subcortical white matter, prominent perivascular hemorrhage, and some mononuclear cell perivascular cuffing. Another donkey and three rabbits fed the cultured corn did not develop characteristic signs or lesions of the toxicosis. Chick bioassay studies indicated that the cultured corn...
Ray AC, Tamulinas SH, Reagor JC.Experimental animals (rabbit, rat, goat, sheep, and pony) were given cantharidin or dried preparations of blister beetles (Epicauta lemniscata) to stimulate naturally occurring toxicosis in which beetles were ingested with alfalfa hay. A sensitive high-pressure liquid chromatographic method, involving derivatization of cantharidin with p-nitrobenzyloxyamine, was developed to detect the toxin extracts of ingesta, fluids, and tissues from these severely poisoned animals. Urine and ingesta from the upper portion of the gastrointestinal tract, containing from 1 to 20 ppm of cantharidin, were the m...
Riemann HP, Kaneko JJ, Haghighi S, Behymer DE, Franti CE, Ruppanner R.Hospitalized animals and stray dogs were serologically tested for antibodies against Toxoplasma gondii. In addition, the data were examined for the possibility of toxoplasmosis infection being associated with the clinical diagnosis and with the discharge status (alive vs. dead). Among 1056 hospitalized animals, 17 (20%) of 86 cats, 112 (14%) of 804 dogs, 34 (26%) of 133 horses and 6 (18%) of 33 cattle had serological evidence of infection with T. gondii. Only 22 (6%) of 342 young (median age = one year) stray dogs were seropositive. The difference in antibody prevalence between hospitalized an...
Dickie CW, Klinkerman DL, Petrie RJ.Two Quarter Horse foals from different premises died from enterotoxemia. Clostridium perfringens toxins alpha and beta were demonstrated in the foal's intestines by mouse protection tests. Clostridium perfringens type C was isolated from the intestines of each foal. Histologic examination revealed hemorrhage, necrosis, and massive numbers of C perfringens.
Ochoa R, de Velandia S.Clostridium perfringens type A enterotoxin seroneutralization was carried out on sera from 50 horses recovered from grass sickness and from 100 other horses with no record of having had the disease. Of the affected horses, 70% had seroneutralizating titers higher than 1:64, half of these being equal or higher than 1:128. More than 88% of the horses with no record of grass sickness had titers lower than 1:64. These data support the theory of association between C perfringens type A toxins and grass sickness.
Sutie JW.Animals normally ingest small amounts of fluorides in their diet with no adverse effect. An increased ingestion of fluoride can be harmful to animals, and grazing animals can be damaged by the consumption of high-fluoride vegetation. Cattle have been the species most commonly affected, and the symptoms of excessive fluoride ingestion in that species include; lesions in the developing dentition, skeletal lesions, lameness, chemical evidence of tissue fluoride ingestion in that species include: lesions in the developing take and decrease in production. The level of fluoride which can be tolerate...
Marasas WF, Kellerman TS, Pienaar JG, Naudé TW.When 2 horses were dosed with cultures of a Fusarium moniliforme isolate that had previously caused only hepatosis, 1 developed brain oedema and hepatosis, and the other only leukoencephalomalacia. A 3rd horse developed both leukoencephalomalacia and hepatosis after being dosed with another isolate obtained from maize which was associated with a natural outbreak of the nervous form of the disease. Since leukoencephalomalacia and hepatosis could be induced by the same culture material, it was concluded that both syndromes were manifestations of the same toxicosis. There was also some evidence t...
Walthall JC, McKenzie RA.Horses grazing manily Cenchrus ciliaris and/or Panicum maximum var. trichoglume pastures on over 30 properties in southern central Queensland developed lesions of osteodystrophia fibrosa. Horses on individual properties in coastal Queensland grazing Setaria anceps, Brachiaria mutica or Pennisetum clandestinum also developed the disease. Ill-thrift, lameness, and fibrous swellings of nasal bones, maxillae and mandibles were observed. Calcium and phosphorus levels of pasture were normal but all the above pasture species contained oxalates which were suspected of causing the disease.
Greenway JA, Puls R.Clinical sickness was observed in domestic ducks, geese, horses and swine during October 1973. All species showed upper alimentary distress with mortalities occurring in the geese. Barley derived from a common source had been fed. Examination of the barley revealed invasion by Fusarium spp and detection of a high level of dermatitic fusariotoxins.
Radvila P.The effect of heterologous and homologous antitoxin is the same if an equal amount of antitoxin is present in the organism. In man there are no circulating antibodies in the blood after the first injection of the toxoid because there is no natural immunity against the tetanus antigen. After the second injection, man develops the same immunity as animals. Large antitoxin doses protect people for a longer period than small doses. Normally 3,000 I. U. of the heterologous antitoxin protects people for 2 to 3 weeks. In man and sheep 2 ml of the adsorbed vaccine produces an earlier and longer-lastin...
Science (New York, N.Y.)May 26, 1975
Volume 188, Issue 4189 738-740 doi: 10.1126/science.1168366
Carter CD, Kimbrough RD, Liddle JA, Cline RE, Zack MM, Barthel WF, Koehler RE, Phillips PE.Tetrachlorodibenzodioxin was identified as the apparent cause of an outbreak of poisoning in humans, horses, and other animals. Exposure was related to the spraying of contaminated waste oil on riding arenas for dust control. The contamination resulted from improper disposal of a toxic industrial waste. The pathologic effects and chemical identification of tetrachlorodibenzodioxin are described.
Hooper PT.Severe spongy degeneration of the central nervous system (CNS) was seen in 11 cattle, 19 sheep, 4 pigs and 1 goat, associated with a variety of hepatic diseases, particularly those caused by hepatotoxic pyrrolizidine alkaloids. It was also seen in a milder form in 2 of 8 horses examined, 1 dog of 5 dogs examined, and in 1 rabbit only of a large number of laboratory animals examined. This paper reports results of experiments which confirmed initially that the CNS disease cold be caused by pyrrolizidine alkaloid intoxication. This was done by poisoning lambs with lasiocarpine. As the disease was...
Obuch-Woszczatyński P, Pituch H, Martirosian G, Silva J, Meisel-Mikołajczyk F, Łuczak M.Seven Bacteroides fragilis strains were cultured from samples collected from horses. From all the tested strains, as well as from the reference B. fragilis strains: enterotoxigenic NCTC 11925 and nonenterotoxigenic IPL 323 strain, DNA was isolated using Genomic DNA PREP PLUS isolation kit manufactured by A&A Biotechnology (Poland). To detect the enterotoxin (fragilysin) gene, polymerase chain reaction (PCR) was applied, using the following starters: 404 (GAG CCG AAG ACG GTG TAT GTG ATT TGT) and 407 (TGC TCA GCG CCC AGT ATA TGA CCT AGT). DNA obtained from bacterial cells was amplified in a ...
Wichtel JJ, Whitlock RH.Botulism was believed to be the cause of progressive symmetric myasthenia in 8 horses on a farm in North Carolina. One horse was found dead, 6 were euthanatized after becoming recumbent, and 1 affected horse recovered. Cecal and colonic contents of 2 horses were determined to contain Clostridium botulinum spores. Alfalfa hay that was fed to the horses contained spores and toxin.
Loch WE, Swantner LD, Anderson RR.Mean weight of 20 Quarter Horse placentas on a wet basis was 3.27 +/- 0.17 kg. These placentas contained mean dry fat-free tissue, DNA, RNA and collagen weights of 411 +/- 24 g, 11.2 +/- 0.6 g, 12.4 +/- 0.7 g and 210 +/- 15 g, respectively. In Ponies and Quarter Horses, there was a trend towards a decrease in these 4 values as gestation length increased. Analysis of placentas of Ponies fed different amounts of endophyte fungus-infected fescue seed showed that weight of dry fat-free tissue increased with increasing percentages of fescue seed in the diet. Diets containing fescue seed resulted in...
Bischoff K, Moiseff J.Feed as a cause of poisoning in horses can occur on small or large scales. It is challenging to work up cases of suspected feed contamination, but there are resources available to veterinarians and owners. Feed contamination can be chemical or biological. This article focuses on and provides examples of chemical feed contamination including misformulation, adulteration, and natural contaminants. Additionally, recommendations for feed sampling and diagnostic submission, including legal documentation, are included.
Kelly AP, Jones RT, Gillick JC, Sims LD.An outbreak of nervous disease in Standardbred horses occurred near Bendigo, in south-eastern Australia, in October 1980. Over a two week period 11 horses in four training stables were affected with gait abnormalities, depression and recumbency. Eight of the 11 died. The results of an investigation implicated Clostridium botulinum toxin as the cause. The toxin was food-borne as a contaminant of oaten chaff.
François AC, Renaud B, Kruse CJ, Marcillaud-Pitel C, Votion DM.Anne-Christine François, Benoît Renaud, Caroline-Julia Kruse, Christel Marcillaud-Pitel and Dominique-Marie Votion of the Atypical Myopathy Alert Group discuss insights from 20 years of research and surveillance on equine atypical myopathy.
Cserhalmi D, Wermer K.Our paper presents a case study of a Welsh pony mare with grazing-induced severe urticaria. The main clinical signs were eye swelling, depression and extensive urticaria. Physical examination revealed no other abnormalities. Botanical sampling revealed horseweed (Conyza canadensis) as the most abundant species and a potential allergen plant due to sesquiterpene lactones (SQL). Differential diagnosis strongly suggested that the clinical signs were the result of a hypersensitivity reaction to this plant. Former studies brought controversial data about the toxic or allergic potential of horsewee...
Mittelman NS, Engiles JB, Murphy L, Vudathala D, Johnson AL.An 8-year-old Holsteiner gelding was presented for evaluation of anorexia, obtundation, icterus, and mild colic signs of 48 hours duration. History, physical examination, and initial diagnostics were suggestive of hepatic disease and encephalopathy. Microcystin toxicosis was suspected based on historical administration of a cyanobacteria supplement, associated serum biochemistry abnormalities, and characteristic histopathological changes. Microcystin contamination was confirmed in both supplement containers fed to the horse. Fulminant hepatic failure and encephalopathy progressed resulting in ...
Sander J, Terhardt M, Janzen N.In horses, congenital defects of energy production from long-chain fatty acids have not been described so far. In contrast, inhibition of fatty acid degradation caused by the toxins hypoglycin A and methylenecyclopropylglycine from various maple species are observed frequently. These non-proteinogenic aminoacids are passed on placentally to fetuses or with collostrum or milk to newborn foals. Nevertheless, newborn foals become very rarely symptomatic. Vertical transmission apparently is not sufficient to induce clinical disease without a particular genetic constellation being present. One of t...
Kamphues J, Meyer H, Liebler EM, Johannsen A.Anamnesis and clinical signs of horses form five different stables after ingestion of ionophores are reported and techniques of feed examination are described. Within a few hours or days after feeding of new types or batches of concentrates horses fell ill. They showed colic-like symptoms with intense sweating and ataxia. Most of the sick animals died within a short time span. Samples of the concentrates were analysed and different types and amounts of ionophores were detected. In four cases contamination by monensin in concentrations of less than 5 mg to 679 mg/kg feed were found. One feed sa...
Johnstone LK, Mayhew IG.To investigate the effects of lolitrem B intoxication on renal K(+) secretion in response to increased tubular flow rates. Methods: Results are derived from a repeated measure pilot study of seven horses fed non-perennial ryegrass feed for a week prior to exposing them to perennial ryegrass seed and hay that contained an average of 2 ppm lolitrem B. At the end of the control and treatment period frusemide (1 mg/kg I/V) was administered and serial fractional excretion of K(+)(FEK(+)) and fractional excretion of Na(+)(FENa(+)) calculated. Baseline concentration of aldosterone in plasma, serum K(...
Durham AE.Outbreaks of liver disease in horses are common but the etiology of most remains unknown. Forage mycotoxins have been suspected to be a cause. Objective: To examine the association between outbreaks of liver disease and the presence of mycotoxins in forage stored on the same premises. Methods: Premises were identified where ≥4 horses were contemporaneously affected by liver disease, and a control group was formed from premises where ≥4 horses had been examined and found to have no evidence of liver disease. Methods: Forage was collected from 29 case and 12 control premises. The forage was ...
Rudolph W, Remane D, Wissenbach DK, Klein C, Barnewitz D, Peters FT.Atypical myopathy (AM) is a fatal disease in horses presumably caused by hypoglycine A (HGA) from ingested maple seeds and its active metabolite methylene cyclopropyl acetic acid (MCPA). The aim of this study was the development and validation of a rapid and simple assay for HGA and MCPA-carnitine in horse serum and its application to authentic samples. Identification and quantification were carried out by ultra high performance liquid chromatography-high resolution tandem mass spectrometry (UHPLC-HRMS/MS) with full-scan/data-dependent MS/MS. Chromatographic separation was performed by isocrat...
Sloet van Oldruitenborgh-Oosterbaan MM, Schipper FC, Goehring LS, Gremmels JF.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...
Tesfaigzi Y.Exposure of airways to environmental toxins or allergens induces proliferation of epithelial cells. Depending on the type of exposure, existing and newly formed cells can differentiate into mucus-producing cells resulting in mucous cell metaplasia (MCM). During recovery, the epithelium reduces the number of epithelial cells to return to the original state. Understanding the mechanisms involved in this resolution could be useful in deleting mucous cells and, thereby, mucous secretions. We have found that metaplastic mucous cells induced by exposure to ozone, endotoxin, cigarette smoke or allerg...
Dos-Santos MC, Yamaguchi IK, Caricatti CP, Higashi HG, Dias-da-Silva W.Equines (2 horses and 2 donkeys) immunized with whole Crotalus durissus terrificus venom or its phospholipase A2 component either presented an increased survival time determined 3 days after challenge or were totally resistant to a challenging lethal dose of 200 mg crude venom 270 days after the initial immunization or 90 days after the last booster injection. The resistance was demonstrable on the basis of a good correlation with antibody titers determined by the ELISA method but not with the flocculation and neutralization assays. Since phospholipase A2 is essentially nontoxic, it can be use...
Lapan G, Awad-Masalmeh M, Hartig A, Silber R.In this study 55 strains of Taylorella equigenitalis isolated from horses of four different studs in Austria, and a comparative strain from the Federal Republic of Germany were investigated by different methods. These investigations were carried out with the help of SDS-PAGE, immunoblotting, the analyses of genomes and by proof of plasmids. Furthermore, pathogenic mechanisms such as adhesion or the formation of toxins were investigated in vitro. On the basis of the results carried out by means of SDS-PAGE and immunoblotting all tested strains of Taylorella equigenitalis were alike, whereas by ...
Muzard J, Billiald P, Goyffon M, Aubrey N.Serotherapy is the only specific treatment for envenomation. The antibodies are obtained after the purification of serum from hyperimmunised horses and are used after fragmentation in the form of polyclonal Fab or F(ab)'2. The anti-venom sera are heterogeneous, and their protective effect is often weak. The administration of these preparations induces risks of immediate or delayed side effects: hypersensitivity reactions, anaphylactic shock and serum sickness. This observation led us to develop new forms of antibodies produced by molecular engineering, capable of specifically neutralizing the ...
Jahn P, Dobešová D, Brumarová R, Tóthová K, Kopecká A, Friedecký D.Equine atypical myopathy (AM also referred to as multiple acyl-CoA dehydrogenases deficiency [MADD]) is thought to be caused by toxins metabolized from hypoglycin A (HGA) and méthylènecyclopropylglycine (MCPrG). HGA is contained in the seeds and seedlings of the sycamore tree (Acer pseudoplatanus); MCPrG has so far only been confirmed in seeds. Among other things, these substances can disrupt the fatty acids β-oxidation pathway with the subsequent accumulation of certain acylcarnitines. The tentative diagnosis is based on anamnesis and clinical signs and can be verified by the detection of ...
Radvila P.The effect of heterologous and homologous antitoxin is the same if an equal amount of antitoxin is present in the organism. In man there are no circulating antibodies in the blood after the first injection of the toxoid because there is no natural immunity against the tetanus antigen. After the second injection, man develops the same immunity as animals. Large antitoxin doses protect people for a longer period than small doses. Normally 3,000 I. U. of the heterologous antitoxin protects people for 2 to 3 weeks. In man and sheep 2 ml of the adsorbed vaccine produces an earlier and longer-lastin...
