Peer-reviewed veterinary case report
Horses showing neurologic signs after ivermectin - what to know
By Swor, Tamara M et al.·Published in Journal of the American Veterinary Medical Association·2009·Department of Large Animal Clinical Sciences, United States·View original on PubMed →
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Original publication title: Ivermectin toxicosis in three adult horses.
- Species:
- horse
Plain-English summary
Three adult Quarter Horses showed serious neurological problems about 18 hours after they were given a dose of ivermectin paste, a medication often used to treat parasites. The horses displayed signs like being very tired, difficulty walking, drooping lips, and muscle twitching. Their pupils were dilated, and they had reduced reactions to light and other stimuli. After supportive treatment with fluids and anti-inflammatory medications, two of the horses recovered without lasting issues, while one horse had to be euthanized due to severe toxicity, which was confirmed by finding high levels of ivermectin in its brain after death. This case highlights that ivermectin toxicity, though rare, can occur and that prompt supportive care can lead to recovery in some cases.
Abstract
CASE DESCRIPTION: 3 adult Quarter Horses were evaluated for acute, progressive neurologic signs 18 hours after oral administration of 1 dose of 1.87% ivermectin paste. CLINICAL FINDINGS: Clinical signs included depression, forelimb and hind limb ataxia, drooping of the superior and inferior lips, and muscle fasciculations. Bilateral mydriasis, decreased pupillary light reflexes, and absent menace reflexes were evident. Clinical signs progressed in severity for 36 hours after administration of the ivermectin. TREATMENT AND OUTCOME: All horses were treated supportively with IV administration of fluids and anti-inflammatory medications. Two horses survived with no apparent long-term sequelae. One horse was euthanized, and a high concentration of ivermectin was detected in its brain tissue at postmortem examination. Analysis of the ivermectin concentration in the paste product revealed that the concentration was approximately that indicated on the packaging. CLINICAL RELEVANCE: Ivermectin toxicosis is an uncommonly reported condition in equids that should be considered when acute neurologic impairment develops after ivermectin administration. Recovery is possible with supportive care and time.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/19719447/