It starts as a small lump. You’re petting your cat, feeling that familiar purr against your palm, and then your fingers hit a hard, marble-sized bump under the fur. Maybe you think it’s a cyst. Or an abscess from a neighborhood scrap. But then you look closer and see it: a tiny, breathing hole in the center of the swelling.
That’s when the panic sets in. Honestly, seeing a wolf worm in cats for the first time is enough to make even the toughest pet owner feel a bit queasy.
Commonly known as "wolf worms," these are actually the larvae of the Cuterebra botfly. They don't want to be in your cat. It’s a complete biological accident, a "wrong turn" in the fly's life cycle that turns your living room predator into an unwilling host. While these parasites are gruesome, they are rarely fatal if you handle them correctly—and "correctly" almost never involves a pair of tweezers and a "can-do" attitude at home.
The Weird Way Your Cat Gets Infected
Most people think botflies bite cats to lay eggs. That’s a myth. The reality is way more "Mission Impossible" than that.
Adult Cuterebra flies are huge, fuzzy, and look a bit like bumblebees. They don't have functional mouthparts, so they don't eat; they just live to mate and lay eggs. They find high-traffic areas—think rabbit burrows, woodpiles, or the tall grass where your cat likes to hunt—and glue their eggs to blades of grass or sticks.
They’re waiting for heat.
When a cat (or a rabbit, the intended host) brushes past, the body heat triggers the eggs to hatch instantly. The tiny larvae—which are microscopic at this stage—hitch a ride on the fur. They don't burrow through the skin yet. Instead, the cat grooms itself, or the larva crawls toward a natural opening like the nose, mouth, or an open scratch. Once inside, they migrate through the body's tissues for about a week before settling down under the skin to grow.
Why do they call them "Wolf Worms"?
The name is old-school folk terminology. In the South especially, hunters would find these massive, grub-like larvae in squirrels or rabbits and noticed they looked "wolfish" or aggressive. In cats, they are most common in the late summer and early fall, coinciding with the peak of the botfly breeding season. If you live in a wooded area or your cat is a frequent "gift-bringer" of local rodents, your risk is much higher.
Spotting the Signs Before Things Get Ugly
You won't know the larva is there for the first week or two. It’s a silent traveler. But as it grows, it needs to breathe. That’s why it creates a "warble"—the medical term for that lump with a hole in the top.
Look for these specific red flags:
- A localized swelling, usually around the neck, face, or chest.
- A clear, circular hole (the breathing pore) in the middle of the lump.
- Matting of the fur around the site.
- The cat obsessively licking or scratching one specific spot.
- A "moving" sensation under the skin if you look very closely at the hole.
Sometimes, things go sideways.
While most wolf worms in cats stay comfortably under the skin, some get lost. Veterinary neurologists at places like North Carolina State University have documented cases where these larvae accidentally migrate into the cat’s nasal passages or even the brain. This is called feline ischemic encephalopathy. If your cat starts circling, acting blind, or having seizures during fly season, a migrating larva is a terrifying but real possibility.
The "Do Not Do This" List
I cannot stress this enough: Do not squeeze the lump. It is tempting. You see a bug, you want it out. But the wolf worm is covered in tiny, backward-facing spines. If you squeeze the cat, you risk rupturing the larva's body. When a Cuterebra larva breaks inside a cat, it releases foreign proteins that can trigger an immediate, life-threatening anaphylactic shock.
Basically, your cat’s immune system goes into overdrive and tries to kill the parasite and the cat at the same time.
You also shouldn't try to "suffocate" it with petroleum jelly or nail polish. People do this with wood ticks or botflies in humans, but in cats, if the worm dies while still inside the warble, it will rot. That leads to a massive secondary infection and a much larger surgical bill at the vet’s office.
How the Pros Get It Done
When you take your cat to the vet, the process is actually pretty fascinating, if a bit gross. Most vets will sedate the cat because the removal is painful and requires precision.
First, they might slightly enlarge the breathing hole using a scalpel. Then, using hemostats (surgical pliers), they carefully grasp the larva. The goal is to pull it out in one whole, wiggling piece. Once it’s out, the vet has to flush the "pocket" with antiseptic. Since the larva was living there, the hole is basically a pre-made abscess.
The recovery is usually fast. Most cats are back to their normal, judgmental selves within 24 to 48 hours. Your vet might prescribe a round of antibiotics or even a dose of a dewormer like Ivermectin, though that’s usually a preventative measure rather than a cure once the worm is already huge.
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Prevention: Keeping the Flies at Bay
Is there a "wolf worm vaccine"? No. But you aren't helpless.
Indoor-only cats are almost entirely safe. If your cat doesn't go out, the eggs can't hitch a ride. However, if you have a "catio" or your cat sneaks out, they are fair game.
Using a year-round flea and tick preventative that includes protection against certain mites and heartworms—like Revolution (selamectin)—has been shown to have some efficacy in killing the larvae before they can establish a warble. It's not a 100% guarantee, but it makes your cat a much less hospitable environment for a wandering parasite.
Also, keep your yard tidy.
- Clear out brush piles where rabbits hide.
- Keep the grass short.
- Discourage rodents from nesting near your porch.
Beyond the Skin: A Warning on Nasal Cuterebra
If your cat starts sneezing violently—we're talking 10-20 times in a row—and has a bloody discharge from just one nostril, the wolf worm might be in the nose. This is a specialized nightmare. Vets often have to use an endoscope to find the larva deep in the nasal turbinates.
It’s expensive. It’s stressful. But catching it early prevents the worm from moving from the nose into the brain. If you see "summer sneezing," don't just assume it's allergies.
Actionable Next Steps for Pet Owners
If you've found a lump on your cat today, here is exactly what you need to do.
- Hands off. Resist the urge to poke, prod, or squeeze. You’ll just make the cat mad and risk a rupture.
- Check for a hole. Use a flashlight to see if there is a distinct opening. If there is, it’s almost certainly a wolf worm.
- Call the vet immediately. Mention "Cuterebra" specifically so they know it might be an urgent removal rather than a routine check-up.
- Monitor breathing. If the lump is near the throat or if the cat is acting lethargic, get to an emergency clinic.
- Secure the perimeter. While your cat recovers, check your yard for rabbit nests or rodent holes. That’s where the "mother ship" is.
Dealing with a wolf worm in cats is a rite of passage for many rural and suburban pet owners. It’s a disgusting, crunchy reality of nature, but with a quick trip to the vet and a "no-squeeze" policy, your cat will be just fine. Just maybe don't look at the larva once it's removed—some things are better left unseen.