TL;DR: Seeing thin, white worms in your cat's eye indicates a Thelazia infection, which is a painful condition requiring immediate veterinary care to prevent permanent eye damage or vision loss.
What are the symptoms and causes of eyeworms in cats?
Seeing a thin, white, thread-like parasite moving across your cat's eyeball or under the eyelid is often a sign of Thelazia, commonly known as the 'eyeworm.' These parasites are typically transmitted by small flies and live in the tear ducts and conjunctival sacs of mammals. They can cause significant irritation, swelling, and discharge.
Is an eyeworm infection in my cat a veterinary emergency?
- The urgency level for this condition is High because eyeworms are extremely painful and distressing for your cat.
- If left untreated, the worms can cause corneal ulcers, chronic inflammation, secondary bacterial infections, and potential permanent vision loss.
- Contact a veterinarian or an emergency clinic immediately to have the parasites safely removed by a professional.
How does taking a photo of my cat’s eye help with veterinary triage?
- If your cat is comfortable enough, capture a clear, high-resolution photo or short video of the eye to share with your vet.
- Worms often retreat behind the third eyelid or into the tear ducts during stressful physical exams, making them difficult to locate in person.
- Visual evidence helps the veterinary team confirm the diagnosis and prepare the necessary removal tools before you even arrive at the clinic.
Clinical Context (Merck Veterinary Manual)
Thelazia californiensis and T. callipaeda are eyeworms found in dogs, cats, and other animals, with T. callipaeda appearing to be spreading in Europe. These whitish worms, 7-19 mm long, move rapidly in a serpentine motion across the eye, with up to 100 worms potentially present in the conjunctival sac, tear ducts, and on the conjunctiva under the nictitating membrane and eyelids. For migrating parasitic larvae, suspect lesions should be explored by carefully enlarging and probing the breathing pore or fistula with mosquito forceps; covering the breathing pore with white petroleum jelly for 10-15 minutes before grasping the parasite can aid removal. Do not squeeze the lesion, as this may rupture the larva and lead to a chronic foreign body reaction and secondary infection, with anecdotal reports of anaphylaxis. Definitive diagnosis of parasitic migration is made by finding and identifying the larva, with CT scans potentially aiding in larval identification in cats.
Chapter: Neurology, Parasitology
Source: The Merck Veterinary Manual, 11th Edition (Page 880)