Peer-reviewed veterinary case report
Unequal pupil size in cats and dogs with tick paralysis
By Holland, C T·Published in Australian veterinary journal·2023·Merewether Veterinary Hospital, United Kingdom·View original on PubMed →
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Original publication title: Static anisocoria in cats and dogs with naturally occurring tick paralysis (Ixodes holocyclus).
- Species:
- dog
Plain-English summary
A 5-year-old Labrador and a 3-year-old domestic shorthair cat were brought in with unusual eye symptoms, specifically one pupil larger than the other (anisocoria), after being diagnosed with tick paralysis from a tick bite. The tick was found far from their heads and necks, which is unusual for this condition. Both pets showed signs of nerve dysfunction affecting their pupils, but after treatment for tick paralysis, their symptoms improved. The study suggests that the tick's toxin can cause these eye issues even when the tick is not located on the head or neck.
People also search for: dog anisocoria treatment · cat tick paralysis symptoms · why is my dog's pupil bigger than the other
Abstract
OBJECTIVE: To characterise the novel occurrence and neuro-ophthalmological features of static anisocoria in cats and dogs with tick paralysis (TP) (Ixodes holocyclus) due to a single tick located remote from the head and neck. DESIGN: Observational case series with retrospective analysis. METHODS: Medical records were reviewed from 69 cats and 169 dogs treated for TP from a suburban veterinary hospital in Newcastle, New South Whales, between September 2005 and October 2021. RESULTS: Anisocoria was observed in 2/18 (11.1%) cats and 3/30 (10.0%) dogs with a single tick located remote from the head and neck. These proportions were not different when compared within species to 4 of 28 (14.3%) cats and 16 of 98 (16.3%) dogs with aniscocoria with a single tick located on the head and neck region (P = 1 and 0.56 respectively). Anisocoria arose from pupillary efferent dysfunction and included unilateral oculoparasympathetic dysfunction (internal ophthalmoplegia) in one dog, unilateral oculosympathetic dysfunction (Horner's syndrome) in one cat and one dog, and a combination of bilateral, but asymmetric, oculosympathetic and oculoparasympathetic dysfunction in one cat and one dog. CONCLUSION: It is proposed that anisocoria in cases of TP with a tick located remote from the head and neck is due to an intrinsic latent asymmetry in the safety factor for pupillary efferent function that is unmasked by a systemically distributed holocyclotoxin inhibiting neural transmission within this system, and this is the prevailing pathomechanism, rather than a direct local effect, underscoring anisocoria with a tick located on the head or neck.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/37574813/