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Retinopathy associated with ivermectin toxicosis in five cats
Jessica M Meekins1, Sarah C Guess, Amy J Rankin
1Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.
Summary
Accidental topical application of horse ivermectin paste in cats caused severe neurological and ophthalmic signs, including blindness. Fortunately, all cats recovered fully without specific treatment, highlighting the potential toxicity of ivermectin in felines.
Area of Science:
- Veterinary Neurology
- Toxicology
- Ophthalmology
Background:
- Ivermectin is a widely used antiparasitic drug.
- Accidental overdosing or inappropriate administration can lead to toxicity in animals.
- Feline ivermectin toxicosis is less documented than in other species.
Observation:
- Five cats presented with acute onset tremors, obtundation, blindness, and dilated pupils.
- The cats had received topical ivermectin paste intended for horses in their ear canals.
- Ophthalmic examination revealed absent menace response, dilated pupils, and decreased pupillary light reflexes.
Findings:
- Electroretinography showed diminished b-wave responses in affected cats.
- Serum ivermectin levels were confirmed at 450 and 610 μg/L in two cats.
- Fundic examinations were unremarkable, with no pathological changes noted.
Implications:
- This case series provides the first description of ophthalmic and electroretinographic findings in cats with ivermectin toxicosis from transdermal administration.
- Clinical signs, including blindness, resolved spontaneously over time without specific medical intervention.
- Emphasizes the risk of using non-feline specific ivermectin formulations and the potential for severe adverse effects in cats.
