Cat Cuterebra (Warble): Skin and Neurologic Signs to Watch

Cuterebra is a bot fly larva that can burrow under a cat's skin, typically creating a visible, breathing lump — but when it migrates to the brain or spinal cord, the neurological signs that follow can be severe and sudden. Early recognition of both the skin warble and any neurological changes is critical for treatment success.

Last reviewed: June 2026

What Is Cuterebra and How Do Cats Get It?

Cuterebra are the larvae of North American bot flies (genus Cuterebra), whose natural hosts are rabbits and rodents. Cats become accidental hosts when they investigate or prey on rodents or rabbits near bot fly egg-laying sites — typically burrows, nests, or vegetation — and the larvae hatch on contact with body heat, then penetrate mucous membranes or skin. Infestation is most common in late summer and early fall, when bot fly populations peak.

After entering the body, larvae typically migrate to subcutaneous tissue — most often the head, neck, or trunk — where they form a characteristic warble: a raised, firm lump with a small central breathing hole (pore) through which the larva periodically protrudes. Most outdoor cats with Cuterebra show only this skin form. The serious complications arise when larvae migrate aberrantly to the brain or spinal cord, causing a condition known as feline ischemic encephalopathy (FIE) or Cuterebra-associated encephalitis, as described in Tilley's The 5-Minute Veterinary Consult: Canine and Feline.

Skin Signs vs. Neurological Signs

Recognizing the difference between simple skin infestation and neurological migration is critical:

Skin (subcutaneous) signs — common:

• A firm, rounded lump under the skin, most often on the head, neck, or trunk
• A small pore or hole visible at the top of the lump
• Occasional movement or protrusion of the larva tip visible at the pore
• Mild swelling, warmth, or discharge around the site
• The cat may groom or scratch at the site excessively

Neurological signs — serious, requires urgent care:

• Sudden behavioral change — disorientation, aggression, apparent confusion
• Circling, head tilting, or loss of balance
• Blindness — often sudden, may be in one or both eyes
• Seizures
• Weakness or paralysis in one or more limbs
• Rapid, involuntary eye movement (nystagmus)

Any cat that developed neurological signs in late summer or fall — even without an obvious skin warble — should be evaluated for Cuterebra migration, as the larva may have entered via the nares or pharynx and migrated directly to the brain without a visible skin stage. Neurological Cuterebra migration carries a guarded prognosis, and outcomes depend heavily on how quickly treatment is started (AAFP-AAHA Feline Life Stage Guidelines, 2021).

Treatment: Never Remove a Warble Without Veterinary Guidance

A key point that surprises many owners: do not attempt to squeeze or pull out a Cuterebra larva at home. If the larva is ruptured during removal, the contents can cause a severe anaphylactic reaction or drive inflammation deep into the wound. Veterinary removal involves:

1. Carefully enlarging the breathing pore with a small instrument
2. Grasping the larva intact with mosquito forceps and extracting it whole
3. Flushing and cleaning the wound thoroughly
4. Prescribing antibiotics to prevent secondary infection

For neurological cases, treatment includes high-dose corticosteroids (to reduce brain inflammation), antiparasitic medications, and supportive care. The prognosis for neurological migration is variable — some cats recover fully, others have permanent deficits or do not survive. As described in Nelson & Couto's Small Animal Internal Medicine, the degree of irreversible ischemic brain injury at the time of treatment is the main determinant of outcome.

When to See a Vet

Call your vet today if:

• You find a lump with a small central hole under your cat's skin, especially on the head or neck
• The lump is growing, warm, or discharging fluid
• Your cat is an outdoor cat that has been hunting and develops any new skin lump in summer or fall
• Your cat is scratching obsessively at a single spot on its head or neck

Go to the ER immediately if:

• Your cat suddenly seems blind, disoriented, or confused
• Your cat is circling, falling over, or cannot walk normally
• Your cat has a seizure
• Your cat's head is tilted and eyes are moving rapidly
• Neurological signs appeared suddenly in a cat that has been outdoors in late summer or early fall

Frequently Asked Questions

Can Cuterebra kill a cat? Yes. While simple subcutaneous Cuterebra infestation is usually treatable with full recovery, aberrant migration of the larva to the brain or spinal cord can be fatal or result in permanent neurological damage. Death can also occur from anaphylactic reaction if a larva is ruptured during improper removal. Prompt, careful veterinary removal for skin cases and immediate emergency care for neurological signs offer the best outcomes.

How do I know if the lump on my cat is a Cuterebra or an abscess? A Cuterebra warble has a distinctive small central pore — a breathing hole — that distinguishes it from a simple abscess. Abscesses from cat bites are also common, particularly in outdoor cats, but do not have a visible pore. Gently parting the hair and looking closely at the center of any skin lump may reveal the pore. Do not probe the hole — bring your cat to the vet for a definitive look.

What is the cost of treating Cuterebra in cats? Uncomplicated subcutaneous Cuterebra removal under veterinary care typically costs $150–400, including examination, sedation or anesthesia if needed, and wound treatment. Neurological Cuterebra cases requiring hospitalization, imaging (MRI of the brain costs $1,500–3,000 at specialty centers), and intensive treatment can run $2,000–5,000 or more depending on severity and duration of care.

Can indoor cats get Cuterebra? Indoor-only cats are at very low risk. Cuterebra infestation is almost exclusively a disease of outdoor or indoor-outdoor cats that hunt rodents or rabbits, or access areas where wild animals nest. If an indoor cat develops a suspicious skin lump in summer or fall, a vet visit is still warranted, but an outdoor history is the primary risk factor.

How can I prevent Cuterebra in my cat? Keeping cats strictly indoors during peak bot fly season (late summer and fall) is the most effective prevention. Regular physical examination of outdoor cats — running your hands over the entire body weekly during August through October — can catch early skin warbles before migration occurs. There is no approved preventive medication for Cuterebra in cats.

Still Not Sure if Your Cat Needs a Vet?

When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of the lump site or the affected area — including close-ups showing any pore or discharge — or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.

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