Corneal ulceration in a dog following exposure to the defensive spray of a walkingstick insect (Anisomorpha spp.)

Abstract

To describe a case of corneal ulceration in a dog resulting from ocular exposure to the defensive spray of a walkingstick insect (Anisomorpha spp.). A 4-year-old, male Chihuahua in southeastern Louisiana presented to an emergency veterinary hospital approximately 20 hours after it was witnessed to have come in close proximity to a walkingstick insect. Within seconds of approaching the insect, the dog yelped, jumped backwards and developed lacrimation, blepharospasm, and periocular swelling of the left eye. Upon presentation, the dog was found to have blepharospasms and miosis of the left eye. Fluorescein stain was applied to the affected eye and diffuse corneal uptake of stain was noted. A diffuse superficial corneal ulceration was diagnosed and treated supportively with ocular flushing, topical antibiotics, ocular lubrication, and a 1% solution of ocular atropine, as well as systemic nonsteroidal anti-inflammatory agents. Clinical signs resolved 10 days after injury. While most species of walkingstick insects are considered harmless, certain species in the southeastern United States have the ability to spray defensive venom at their predators. Upon ocular exposure to the venom, the victim may experience intense pain followed by blurred vision, conjunctivitis, keratitis, and corneal ulceration. To date, there is only 1 previous reported case of ocular exposure to walkingstick venom in a dog although both children and animals may be at higher risk for ocular exposure due to their curious nature and proximity in size to the insect. Superficial corneal and conjunctival damage can occur following direct exposure to the defensive chemical spray of the Northern and Southern Twostriped walkingstick insects found in the southeastern United States and may be considered a differential diagnosis in cases involving diffuse corneal ulceration.