Diagnostic value of tissue monensin concentrations in horses following toxicosis.
Abstract: Two separate incidents of monensin exposure in horses resulting in toxicosis provided insight into the diagnostic value and interpretive criteria of various biological samples. In case 1, 25 horses broke into a shed and ingested feed that was supplemented with 800 g/ton (880 µg/g) of monensin. Within 48 hr, 1 horse had died, 2 developed cardiac arrhythmias, lethargy, and recumbency, and another was euthanized due to severe deterioration. Minimal histologic lesions were noted in the horse that died peracutely, while another showed characteristic lesions of acute cardiomyocyte degeneration and necrosis. Stomach content, heart, liver, urine, and serum revealed various detectable concentrations of monensin in clinically affected and unaffected horses with known exposure. In case 2, a pastured horse had access to a mineral mix containing 1,600 g/ton (1,760 µg/g) of monensin. Within 48 hr, the horse became symptomatic and was euthanized because of severe respiratory distress. Histologic cardiac lesions were minimal but detectable amounts of monensin were found in blood, heart, liver, and stomach contents. In both cases, monensin toxicosis was confirmed with toxicological analysis. These cases demonstrate an overall lack of correlation of monensin concentrations in various biological samples with clinical outcome. However, serum, urine, blood, liver, heart, and stomach content can be tested to confirm exposure. More importantly, the consistently higher concentrations found in heart tissue suggest this is the most useful diagnostic specimen for postmortem confirmation of toxicosis in horses especially in cases in which associated feed cannot be tested for monensin or in cases with no histologic lesions.
© 2014 The Author(s).
Publication Date: 2014-03-12 PubMed ID: 24621846DOI: 10.1177/1040638714523774Google Scholar: Lookup
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- Journal Article
Summary
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The research article focuses on two incidents of monensin poisoning in horses and evaluates how different biological samples can be used for diagnosing the condition. It concludes that while the monensin concentration in various samples lacks correlation with clinical outcome, heart tissue proves to be the most indicative specimen for postmortem diagnosis.
Context of the Study
- The research was triggered by two distinct instances of horses being exposed to monensin, a potent ionophore used for growth promotion and coccidiosis prevention in some livestock but which is toxic to horses.
- These cases gave researchers an opportunity to study the diagnostic value and interpretive criteria of various biological samples, such as stomach content, urine, blood, liver, heart, and serum, in confirming monensin poisoning.
Case 1
- 25 horses broke into a shed and consumed feed supplemented with monensin. In less than 48 hours, one horse died, two developed symptoms of toxicosis like cardiac arrhythmias and lethargy, and another was euthanized due to severe deterioration.
- Minimal histologic changes were observed in the horse that died while one showed acute cardiomyocyte degeneration and necrosis characteristic of monensin toxicosis.
- Various concentrations of monensin were detected in the horses’ biological samples, irrespective of their clinical state.
Case 2
- A grazing horse consumed a mineral mix laced with a higher concentration of monensin than in the first case. Within 48 hours, the horse developed clinical signs and was euthanized due to severe respiratory distress.
- Minimal cardiac lesions were found during histologic examination, but detectable monensin quantities were present in the blood, heart, liver, and stomach contents.
Key Findings
- Despite the varying levels of exposure and different biological samples tested, monensin poisoning was confirmed in both cases through toxicological analysis.
- No direct correlation was found between the concentration of monensin in the various biological samples and the clinical outcome, implying exposure confirmation can’t be used to predict symptom severity.
- The study revealed consistent high concentrations of monensin in the heart tissue from both cases, suggesting that this is the most valuable sample for postmortem diagnosis. This is especially helpful when associated feed can’t be tested for monensin or in cases where histologic lesions are absent.
Conclusions
- While the concentration of monensin in various biological samples may verify exposure, it doesn’t correlate with clinical outcomes or the severity of the symptoms.
- As monensin concentrations were consistently higher in the heart tissue, this appears to be the most useful sample for confirming monensin toxicosis after death, especially when feed testing isn’t possible or histologic changes aren’t observed.
Cite This Article
APA
Bautista AC, Tahara J, Mete A, Gaskill CL, Bryant UK, Puschner B.
(2014).
Diagnostic value of tissue monensin concentrations in horses following toxicosis.
J Vet Diagn Invest, 26(3), 423-427.
https://doi.org/10.1177/1040638714523774 Publication
Researcher Affiliations
- California Animal Health and Food Safety Laboratory System (Bautista, Tahara, Mete, Puschner), School of Veterinary Medicine, University of California, Davis, CADepartment of Molecular Biosciences (Puschner), School of Veterinary Medicine, University of California, Davis, CAUniversity of Kentucky Veterinary Diagnostic Laboratory, Lexington KY (Gaskill, Bryant).
- California Animal Health and Food Safety Laboratory System (Bautista, Tahara, Mete, Puschner), School of Veterinary Medicine, University of California, Davis, CADepartment of Molecular Biosciences (Puschner), School of Veterinary Medicine, University of California, Davis, CAUniversity of Kentucky Veterinary Diagnostic Laboratory, Lexington KY (Gaskill, Bryant).
- California Animal Health and Food Safety Laboratory System (Bautista, Tahara, Mete, Puschner), School of Veterinary Medicine, University of California, Davis, CADepartment of Molecular Biosciences (Puschner), School of Veterinary Medicine, University of California, Davis, CAUniversity of Kentucky Veterinary Diagnostic Laboratory, Lexington KY (Gaskill, Bryant).
- California Animal Health and Food Safety Laboratory System (Bautista, Tahara, Mete, Puschner), School of Veterinary Medicine, University of California, Davis, CADepartment of Molecular Biosciences (Puschner), School of Veterinary Medicine, University of California, Davis, CAUniversity of Kentucky Veterinary Diagnostic Laboratory, Lexington KY (Gaskill, Bryant).
- California Animal Health and Food Safety Laboratory System (Bautista, Tahara, Mete, Puschner), School of Veterinary Medicine, University of California, Davis, CADepartment of Molecular Biosciences (Puschner), School of Veterinary Medicine, University of California, Davis, CAUniversity of Kentucky Veterinary Diagnostic Laboratory, Lexington KY (Gaskill, Bryant).
- California Animal Health and Food Safety Laboratory System (Bautista, Tahara, Mete, Puschner), School of Veterinary Medicine, University of California, Davis, CADepartment of Molecular Biosciences (Puschner), School of Veterinary Medicine, University of California, Davis, CAUniversity of Kentucky Veterinary Diagnostic Laboratory, Lexington KY (Gaskill, Bryant) bpuschner@ucdavis.edu.
Citations
This article has been cited 2 times.- Ahmadzadeh-Gavahan L, Hosseinkhani A, Palangi V, Lackner M. Supplementary Feed Additives Can Improve Lamb Performance in Terms of Birth Weight, Body Size, and Survival Rate. Animals (Basel) 2023 Mar 8;13(6).
- Bischoff K, Moiseff J. Equine feed contamination and toxicology. Transl Anim Sci 2018 Feb;2(1):111-118.
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