Treatment Of Cuterebra Larva Infestation In Cats And Dogs

 Cuterebra.  Pronounce it CUTE-uh-REE-bruh.

They are anything but cute.

Cuterebra is a bee-like fly which lays her eggs in places where target mammals will come in contact with them. Such locations as the orifices of bird and squirrel nests, burrows and animal paths are favorites. Eggs may be laid on stones or vegetation. The fly’s goal is to get the eggs onto the coat of the host, from which the egg responds to the host’s body heat by hatching to a larval stage. The larvae then enter the mouth or nose during grooming. Less often an open wound on the body might be the entrance point.

Left: 3rd instar larva, Cuterebra spp. Right: 2nd instar larva, Cuterebra spp.
Left: 3rd instar larva, Cuterebra spp. Right: 2nd instar larva, Cuterebra spp.

The larvae then migrate to a subcutaneous (under the skin) spot on the body where they can make a tiny opening through the skin for breathing. The larvae spend about a month in the host, after which they emerge through the skin, fall to the ground and pupate (enter a cocoon stage).

Insect larvae undergo stages called “instars.” Early in the season, such as April and May we expect to see the second instar, which is 5-10 mm. in length and light in color. The third instar is much larger, as big as a child’s thumb, and much darker. They are usually adorned with spines.

So, under what conditions would a veterinarian interact with a Cuterebra larva? Dogs and cats are aberrant hosts, but do sometimes become infected. Wild rabbits and squirrels are the most common victims and can sometimes have a dozen or more Cuterebra cysts at once.

When a cat or kitten is presented to a veterinarian with a Cuterebra (colloquially called a “wolf” or “wolf worm”) the owner is typically baffled by the condition. The sight of “something” moving inside the wound is quite alarming. I say “cat or kitten” because, while dogs are reported to become infected with Cuterebra, I’ve not seen an affected dog in thirty years of practice.

Treatment starts with light sedation of the cooperative patient or general anesthesia of a cat who resists help. Hair is clipped from the area of the cyst and the entire clipped area is disinfected and prepared for surgery. Operating forceps are used to enlarge the opening sufficiently to allow extraction of the larva without undue compression. Rupture of the larva can lead to release of foreign material that may prevent the wound from healing. In some cases anaphylactic shock may take the patient’s life. The wound is thoroughly irrigated per standard abscess-treatment protocol.

Systemic antibiotics are indicated, and I have successfully used Convenia in Cuterebra victims. Ointments, such as Animax, are useful to irrigate the wound and help control infection topically while a systemic antibiotic works from the inside.

Prevention is mainly focused on keeping one’s cat indoors, instead of nosing around where cats don’t belong.

See you tomorrow, Dr. Randolph.

106 Comments

  1. Im not sure if I am in the right category sense I don’t know the issue much but I have a cat that is about 9 years old. I found a lump under her chin and when I went to look at it found 3 smaller holes and one larger one all open, the lump by the large one. i got 2 little white things from it not sure if puss or worse case larva, it wasn’t moving to what i could see. there is another little white thing under the inner skin of the larger hole. I am really worried what it could be…

  2. Hi
    I have a cat which is 6 years old he has got cuterbra its been 3 days something coming out and breathing and goes inside there are more than 15 small worms like.
    What will happen if no treatment is taken? Will it cure automatically? Will it cause any infection to human? Is there any home treatment?

    Waiting for your reply
    Thank you

    • The life cycle of the fly is such that it will eventually mature and fly away. The purpose of treatment at a doctor’s office is to minimize pain and prevent/treat infection. You could be infected only in the same way your kitty was. Thanks for reading MyPetsDoctor.com.

      • do cats always die from this my little cat had this i took her to the vet and they treated her for it and then i had to take her back today and they told me she had kidney failure and liver was failing and i had to have her put down.

        • We are so sorry for the loss of your little baby. I may be going out on a limb here, but I feel pretty confident in saying your kitty didn’t die from the Cuterebra. While I have seen allergic reactions to the rupture of a larva, I’ve never seen a medical report of kidney and/or liver disease associated with them. Thank you for reading http://www.MyPetsDoctor.com.

  3. I rescued 2 kittens that had warbles with cuterebra larvae. I removed the parasite myself. There was a 3rd kitten who had no signs of a warble. However the day after i removed the parasite from the other kittens the 3rd kitten had developed a unsteady gait and he was falling over. I immediately suspected he to had a cuterebra. He also had sneezing without signs of URI days before. I immediately rushed him to my vet that disagreed with my diagnosis and refus8es to give the ivermectin until 24 hrs later when i presented him with the literature. He gave thw meds but still doesnt believe the kitten had this. This happened a month ago. The kitten is now home but he is not right. He cant walk without falling over. He did circle to the left but that has stopped. He eats on his own but all he does is sleep. He has come somewhat aggressive which seems to be from fear..i took him to a neurologists who says its central vestibular syndrome.he recently start8es playing but not for long because he is so tired. The vet wanted me to euthanize him but im still hopeful he will improve. My question is what is the likely hood this is cuterebra and can he recover? It seems every 2 days he improves slightly. I just dont know what to do at this point and if has a chance of getting better

    • That’s a tough situation, Angela. As you have probably surmised, the neurologist who examined him has the best chance of giving you an accurate prognosis. Still, what do you have to lose by giving him a chance, as long as he is not incontinent and continues to eat. Thanks for reading MyPetsDoctor.com.

  4. My 16 month old morkie was infected with one of these Cuterebra larvae, we have many chipmunks and red squirrels on our property. He loves to hunt for them and this is most likely where he picked it up. He was itching and licking the site where the larvae was and it was so inflamed and red he wouldn’t let us touch him or even move his leg… Took him to the vet and had it removed from his groin area. I had no idea what cuterebra was before yesterday. But I forgot to ask the vet if there could be more larvae in his body and could they mature at different times? Just wondering if we were out of the clear or should I worry that there are more and they could be in other spots that we can’t see.

      • My labradoodle puppy had a cuterebra lump removed last month, and now has another simliar lump in the same site on her belly! It seems like the infestation has come back — how is this possible?

        • While it sounds odd, and certainly unusual in my experience, it’s certainly understandable. Whatever made the first fly like that location could easily make another fly like the same, or nearby, spot. Thanks for reading, Dr. Randolph

        • Hi Anna, what was the diagnosis in this situation? We are experiencing a similar problem as a lump has form where the previous larvae was.

  5. my boyfriend just took one out my kitten which is almost 6 months old she isn’t aloud out doors could of she had this awhile and now that it’s out what should i give her now worried about my big cat he goes in and out i checked him but no lumps.

  6. Hi! Would one of these parasites cause prolonged sneezing fits with sometimes thick mucus/blood? Our cat has something going on in his sinuses we can’t figure out. It’s been getting progressively worse over the past year.

  7. Hi,

    My cat is an outdoor cat and now in the summer time he likes to sleep in the neighbors flowerbed, where it’s a bit cooler (I live in Madison, WI).

    A week ago (or more) he started to sneeze, just here and there and I figured that he is probably allergic to something (maybe pollen).

    Thursday-Friday: He then started to get a runny nose (this might have started earlier but this is when I noticed it). The day after he would get these “attacks” as if he couldn’t breathe, and by this point he wasn’t really sneezing anymore, but he did have a runny nose.

    Saturday: he did eat, but not as much as he normally does. Well he usually eats all his food at once, but now he left most of the food and ate a little bit from it throughout the day (but would never finish the breakfast).

    Saturday-Sunday: He then started gagging, as if he wanted to throw up, but he never threw up. He would do this several times during the day.

    Sunday: Again didn’t eat all his food and had his breathing attacks and gagging attacks. In the evening I gave him his dinner, wet food, he didn’t finish it all. After about 10 minutes he started gagging, this time actually throwing up. I went over to him and saw a larvae in the puke, and at that point I decided I really do need to see a vet. (I had been debating if he needed to or not, because he kept seeming better, then worse, and better so I wasn’t sure how bad it was).

    I looked through the internet and figured out that this is most likely a cuterebra, but how did he ingest it. I figure that maybe it went through the nose..?

    He continued gagging afterwards, and Monday his appetite was still low, breathing attacks and gagging.

    I called a vet early Monday morning and got an appointment in the afternoon, and took him in. She looked at the picture of the larvae (I didn’t save the larvae but documented it) and confirmed that this was indeed a cuterebra. She said he’s lucky to be alive because she thought he might have managed to cough it up from the lungs!?? I said my theory was that maybe it came in through the nose? But she said that is really rare (but shouldn’t the other route also be very rare?). This larvae was probably a 2nd stage larvae, because it was fairly small. Also he (the cat) didn’t have any lumps or anything on his neck or body, as far as she could tell, and me too. She gave me antibiotics (Clavamox 125mg) that I should give him twice a day, and told me to get back if he wasn’t better in about 5 days.

    Now my question, shouldn’t she look through his nose or throat maybe to confirm that there aren’t anything else irritating him, another larvae (I know they usually are single events but still), grass anything. This since he is still gagging and has his breathing attacks. I am worried that there might be something else stuck there. Obviously I will take him back on Friday if this still persist, but It seems like she could have confirmed nothing else is bothering him? It seemed to her that it is extremely rare that cats (or dogs) throw up cuterebra, is it? And how do they get inside, could the larvae have migrated in through the nostril (Explaining why just one of the nostrils seem to be plugged up) or is the runny nose just a side effect of the cuterebra itself. My vet said that it is really common to see these signs of common upper respiratory symptoms in cats that has or have had cuterebra, as if they leave some type of toxin.

    My other thought is that maybe this cuterebra was just a rare coincidence, that something else is actually wrong with him? I guess only time will tell.

    Now I am scared to death and don’t want to let my cats out at all, even though they will be very miserable inside. Maybe I will start with supervised outside visits.

    Thanks for a great website.

    • I’m no parasitologist, but I’m reasonably certain a Cuterebra wouldn’t survive in the gastrointestinal tract; rather, I believe it would be digested. If it took an aberrant path it could have ended up in the lungs. Then, again, it might not be a Cuterebra at all. You could ask your veterinarian to ask her parasitology professor for his/her opinion. You could email the picture to her and she could forward it to her alma mater. It wouldn’t hurt to perform a stool test for lungworms, such as Capillaria. And, keep in mind, what’s going on in his nose could be related or unrelated. As for looking inside the nose, it’s not as easy in dogs and cats as people. Structurally, there is tissue in the way that people don’t have. It never hurts to look, though. I found a tiny portion of a blade of grass sticking out of a patient presented for nosebleed a few weeks ago. I wouldn’t have seen it if I hadn’t looked. Or, if it had been a little further in.

  8. I took my cat to our vet a week ago because his right eye was swollen. We thought it was a scratch that was inflamed from playing too rough with the other cats and the vet thought the same. Went home with antibiotics and an ointment to prevent infection. Now a week later, the swelling has not gone down and the wound opened up last night, revealing a pinpoint hole surrounded by a yellowish-tannish area. This now appears to be a wolf worm. We are getting him in to see a different vet as soon as possible, but I have a few questions until then.. Is this something that the vet should have caught when I first brought him out, or is it common to misdiagnose until the breathing hole is visible? Where this is located on his eyelid, should we expect/ prepare for damage from it being in there for at least a week already and so close to his brain? I’m just very worried for my cat and am hoping for some reassurance that he’ll be fine once we get it removed since we caught it somewhat early (at least not 30 days later when it comes out on its own) and are being as proactive as possible. Thank you in advance for any input.

    • Doctors are frequently criticized for failing to find fault with our peers, but, in this case, I think your veterinarian deserves a pass. Not only a pass, but a second visit with your kitty. YOU thought it was an injury, HE/SHE thought it was an injury and it was treated symptomatically. It’s probably what I would have done in the same situation, although, I must add, I haven’t seen the patient and can’t comment in exact terms. Just this week I was reminded of a case from years ago. Monday, one of our regular clients called, frantic that she came home from work, blood was everywhere, and more was coming from her dog’s nose. We instructed her to come straight over to the clinic, whereupon careful examination I found the tiny trailing edge of a three-inch-long blade of grass, administering tiny “paper cuts” to the inside of the patient’s nose. With forceps I was able to grasp the grass and remove it. A phone conversation a few days later confirmed that nothing else was going on and the little dog was now fine. Contrast that to the previous case, in which a kitty presented with recurrent sneezing. After careful and thorough examination, I determined the cat appeared to be suffering from an upper respiratory tract infection. I administered antibiotics. A few days later the owner called to let me know the cat sneezed out a blade of grass, which, days earlier, had not been visible, even with my careful and thorough examination. The client was understanding, continued the antibiotic so that the “paper cuts” inside the nose would not become infected, and everything turned out fine. Proper removal of the Cuterebra larva, and your kitty should also recover uneventfully. While I’ve never diagnosed a brain migration of a Cuterebra larva, and don’t claim to be an expert, I believe most of them enter the nasal passages to enter the brain, when that occurs. Your kitty’s larva is visible from the outside, and removal should be curative. I always treat these as abscesses after removal, so the medications you already have should be curative, barring complications. Please write back and let us know how it goes.

  9. First off I have 24 cats 10 grown 14 kittens under 4months old. My grown cats like to hunt pack rats and bring to kittens all while teaching them to hunt.We live in country so I don’t mind helps keeping rats down but I’m concerned for kittens and cats and myself with hubby.we recently found a stage3 larvae on a huge rat cats had they been brining rats to kittens all month.we just noticed the worm a day ago are they at risk if ate rats with worm and what’s the health risk for my husband and I? Help scared

    • The rat is the intermediate host, and the larva stage of the ultimate fly is the maggot under the rat’s skin. The larva is much less interested in you than you are in it. He cannot complete his life cycle by infecting a human. You are safe. At least from that. Now, Toxoplasmosis from the rats, that’s a different matter… Thank you for reading MyPetsDoctor.com, Dr. Randolph.

      • I just had to put my Cairn to sleep. What we thought may have been Lyme disease turned out to be a bot fly larvae that had entered through her eye and burrowed into her brain. She had massive seizures and brain damage. The vet said she had never seen this before. I dearly wish she never had to. Still reeling.

  10. Can someone help me please? My cat came in and I was petting her and looked at her throat and at first I thought it was a tick so I got my grandmother but when she moved the fur it was like a oval bubble of blood hanging on to her neck and she barley touched it and it just exploded and then right under it was a like hole scab and has a core. It hurts her when we touch it so we don’t know what to do… She scratches it to death and I don’t know if it is a wolf worm or a tick head stuck or what????? Help plz

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