AAEP Annual Convention San Diego 2008
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Ivermectin Toxicosis in Three Adult Horses.

Author(s):
Swor T.M.,
Whittenburg J.L. and
Chaffin M.K.
In: AAEP Annual Convention - San Diego, 2008 by American Association of Equine Practitioners
Updated:
DEC 10, 2008
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1. Introduction

Ivermectin toxicosis is an uncommonly reported condition in equidae. This study describes the history, clinical signs, treatment, and outcome of horses with acute ivermectin toxicosis after routine administration of commercial ivermectin paste.

2. Materials and Methods

Medical records of three healthy adult Quarter Horses presenting with acute, progressive neurological signs were evaluated. All received a single, appropriate oral dose of 1.87% ivermectin (0.2 mg/ kg) paste 18 h before clinical signs.

3. Results

Presenting horses were obtunded, and they exhibited fore and hindlimb ataxia, muscle fasciculations, and flaccid upper and lower lips. Bilateral mydriasis, decreased pupillary light reflexes, and absent menace reflexes were noted. Severity of clinical signs progressed for an additional 36 h. Horses were treated supportively. Two horses survived, and one horse was euthanized because of the severity and progression of signs. Necropsy results identified high levels of ivermectin within the brain tissue. Paste product concentrations were within normal limits.

4. Discussion

Ivermectin seems able to cross an impaired blood/ brain barrier, resulting in clinical signs similar to those reported in other species. Contributing factors may include consumption of toxic plants (silverleaf nightshade), genetic conditions, and incorrect dosages. Recovery from ivermectin toxicosis is possible with supportive care and time.

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How to reference this publication (Harvard system)?

Swor, T., Whittenburg, J. and Chaffin, M. (2008) “Ivermectin Toxicosis in Three Adult Horses.”, AAEP Annual Convention - San Diego, 2008. Available at: https://www.ivis.org/library/aaep/aaep-annual-convention-san-diego-2008/ivermectin-toxicosis-three-adult-horses (Accessed: 14 September 2024).

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