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”) 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.

33 Comments to “Treatment Of Cuterebra Larva Infestation In Cats And Dogs”

  1. Judy 20 August 2012 at 7:32 am #

    My daughter’s dog recently had one of these removed from her side. The larva had died and was threatening to become abcessed. The poor dog had to be shaved and put out in order for the vet to remove the good-sized cutereba. Last week when my daughter returned to have the dog checked up the vet said she had removed 3 others in a week, 2 in kittens and one in a puppy. This took place in the Springfield, MA area. So gross and disturbing!!

    • Dr. James W. Randolph 20 August 2012 at 12:15 pm #

      Yep, Judy, this is the time of year we will see more and more Cuterebra larvae. Our back porch has tons of squirrels who come to our feeders, and we will be seeing lots of Cuterebra on them, too. Thanks for writing.

  2. Chuck 6 July 2012 at 12:33 pm #

    Dr. Randolph, I saw you mentioned haven’t seen a wolf (Cuterebra) larvae in a dog in 30 years. Well I wish I had a picture. I have a Morkie and he had a good sized larva in his neck. My veterinarian was able to remove it. There was a pencil-sized hole in which the larva could be seen moving around. Very gross indeed. I live in the Atlanta area and in a fairly heavily wooded yard. I’m thinking lots of squirrels and chipmunks around may have been the reason. Regards, Chuck.

  3. Brandy 22 May 2012 at 6:34 pm #

    Hello, while I was petting my cat today I noticed a tiny, slimy, white worm-like creature near and around its butt. I have noooo idea what it is and they got on my arm and were moving!!! Do you have any idea what these little things may be?? My cats are indoor cats and I have never seen anything like this before!!!

    • Dr. James W. Randolph 22 May 2012 at 7:22 pm #

      Brandy, I can only surmise, not having seen the “creatures” you saw, but I suspect they are feline tapeworms, probably Dipilydium caninum. Click here to read about tapeworms. You should call your veterinarian, describe what you saw (give the size, color and whether the creatures were flat or round) and ask him whether he wants to dispense medication or whether he wants to see your pet first. Save one or more of the creatures in a moist paper towel if you can, and wash your hands thoroughly.

  4. Pammy 20 October 2011 at 9:16 pm #

    Dear Dr. Randolph, I got your reply. Just wondering if you could tell me what kind of tests are run to see if pets have cancer. I have not seen any more bites on him at all. But I will continue to look for them. I am so scared if he has Cuterebra in his body. Pleae let me about the test for cancer. Thank you Verry much. Pammy

    • Dr. James W. Randolph 20 October 2011 at 9:31 pm #

      Pammy, the last time I wrote I suggested that you take your dog to see his veterinarian. There is no one test for cancer. Tests are different according to the type of cancer suspected. What if you are worrying for nothing? Your veterinarian can tell you if your dog has cancer. Your veterinarian can tell you if your dog has Cuterebra. First thing Friday morning, call your pet’s doctor and make an appointment so you can know where he stands. Again, please let us know what you the doctor says, Dr. Randolph.

  5. Pammy 13 October 2011 at 10:31 am #

    I have a small dog who has little scabs on him all summer. One at a time that is. When I would pick off the scab and squeeze it blood squirted out. No pus. Also a tiny hole would be left behind. He has had a least six on him. But no infection. I’m scared this might be Cuterebra. Please help. Thank U,Pammy

    • Dr. James W. Randolph 19 October 2011 at 11:02 am #

      Pammy, it’s certainly possible that these could be Cuterebra lesions, but they could also be infection, cancer. Since it could be serious, and you’re scared, let’s go ahead and make an appointment with your veterinarian and find out exactly what they are so he can be on the road to recovery. Keep us posted so we, too, can know what’s going on. Best wishes, Dr. Randolph.

  6. A Webster 3 October 2011 at 9:53 pm #

    My farm dogs are always catching moles and eating many of them. My youngest Lab is about 14 months old. I observed her coughing, like she was trying to throw up. I put her outside. I found 2 large pink larvae on the floor and threw them out, not realizing that was what was making her cough. A few days later my husband found a dried up one in the dog bed. I showed it to my veterinarian and he confirmed that it was a Cuterebra. I worm my dogs regularly, and was told they should be wormed for tapeworms. Will this get rid of any more larvae that she may have ingested? Thank you.

  7. Peg 14 September 2011 at 12:24 pm #

    Dr. Randolph, my puppy recently had a Cuterebra larvae removed. I was wondering, would it have been safer for the fly to develop and self-extract itself for a 9 week old pup vs. surgery. Also, what would the surgical procedure typically cost? Any comments would be helpful. As a new pet owner I just want to do the correct thing by my pup in the future.

  8. tcacciato 13 September 2011 at 5:51 pm #

    A family member’s dog just had this and they want to bring the dog with them for a visit. I am 8 weeks pregnant, is this safe for me and my unborn baby?

    • Dr. James W. Randolph 13 September 2011 at 6:22 pm #

      Tracy, I am going to ask you to speak to your physician for an answer to this question. It is a matter of potential medicolegal complications and he is the best person to advise you. Congratulations on your pregancy and best wishes with your new baby, Dr. Randolph.

  9. ourayvet 31 August 2011 at 10:31 am #

    Doc, great article. Thanks for putting it out there. I email the link to my clients. I dont know where you live but in my practice of almost 15 years in Colorado we see them in dogs every year. I’ve seen a couple of dogs with them already this season.

  10. Chanda 18 August 2011 at 4:57 pm #

    Today while petting my Pug I noticed scabby bits stuck to his fur and when I pushed aside his fur I found an area of pus. I was unsure what to do with it so I took him to my mother in the next room. She squeezed the sides and a long stream of pus came out and there was a hole left. He did not exhibit any signs of pain during this and sat as if unaware of what we were doing. My mother noticed a lump a while before but now it is a hole. I am extremely worried now that I think it is a Cuterebra hole. Is it a bad thing that my mother squuezed the pus out? Does it sound like this is what it could be?

    • Dr. James W. Randolph 19 August 2011 at 3:41 pm #

      Chanda, a couple of possibilities come immediately to mind. Most likely your Pug has a sebaceous cyst that has ruptured and leaked its contents out onto the skin and hair (helped along by your mother). Read about sebaceous cysts here. The other possibility is that your dog may have a Hot Spot. Read about Hot Spots here. If he has a sebaceous cyst it won’t need medical attention unless it fails to heal, which is a common complication when they become open (or are opened by our mothers). Hot Spots, on the other hand, require a doctor’s care. Your veterinarian will know what to do. Best wishes, Dr. Randolph.

  11. Catherine Traversone 16 August 2011 at 7:45 pm #

    I am a veterinarian’s assistant. We recently lost a cat who had Cuterebra. It went up the nasal passage to the brain. I’ve never seen a cat howl and act like that. It was horrible. The cat died before we actually knew what the diagnosis was. Since they went up the nasal passage there was no hole to give us a clue. We thought it was some neurological problem and referred to a specialist in a 24 hour hospital. They were the ones who diagnosed it. Evidently they see more of this than we do. This is another reason pets should be kept indoors!!!!!

  12. Heidi 20 July 2011 at 9:40 am #

    Our cat has some hard object just below knee joint. We tried to clip the hair around it to see if we could loosen it. It does not seem to be attached to the main part of her leg, but it may be underneath the skin. Although we had her front legs restrained in order to examine the area, she did not seem to be in pain, but remained calm. We also noticed a small hole next to this. It is not red or inflamed. Could this be a Cuterebra?

  13. valerie 24 June 2011 at 12:45 pm #

    I noticed little white worm-looking things on the table where my cat was lying. He is an indoor cat. What could it be? And is it harmful if not treated? I am concerned about this because I have children in the home.

  14. Mandy Allen 2 June 2011 at 4:00 am #

    I believe my cat has a Cuterebra. Does anyone know how much the veterinarian will charge to have it removed?

  15. Ray Willard 15 September 2010 at 10:32 am #

    A Cuterebra infested our Yorkie. We thought it was a bite mark from a fight with another dog. Seven days after the opening was noticed, which we thought was a bite mark we took the dog to a groomer for a haircut and she noticed the worm in the dog’s hair. After checking the Internet we determined what was happening. It was lucky timing that the grooming took place at the time the worm came out of the dog’s body and was identified. The bathing prior to the haircut cleaned the wound area–things look good. I will take the dog to a veterinarian for further checking to see if more infestations are present.

    • Dr. James W. Randolph 16 September 2010 at 2:19 pm #

      Ray, you are on the right track. While your pet is being seen by his doctor you may also find that he wishes to begin antibiotic therapy, as these wounds are often infected. Best wishes, Dr. Randolph.

  16. Mark Youhana 6 July 2010 at 11:41 am #

    Before anything, I would like to thank you for your comment and interest to help me. Really I am very happy that you responded. The second point that I should make it clear is I don’t trust veterinarians in Egypt, not based on judgement but from experience, so going to a veterinarian is not on my priorities list. Now let me describe my kitty situation, I noticed a black thing out from her head like this thing wanted to breathe.
    Then I searched the web until I have found that it’s a larva and I shouldn’t interact with it or I will make my kitty have an allergy. Till this moment the cat is fine and it’s nearly 7 months since the larva was noticed.
    But I’m still worried and all I can do is to ensure that the spot is clean and no infection. Again I appreciate and respect your kindness. Thanks and I will let you know of any news appetite.

    • Dr. James W. Randolph 13 July 2010 at 8:36 pm #

      Mark, this is the reply from Tim Lockley, PhD entomologist: Am I to assume that the individual is currently in Egypt? If so, his cat may have any one of a number of fly larvae (screwworms, Tumbu fly, et cetera) living just below her skin. If it is a maggot, it will eventually emerge to pupate. Once it’s outside of the cat’s body, the wound can be treated with antibiotics and stitched closed if necessary. Another possibility is a subcutaneous roundworm. They extrude portions of themselves to lay eggs. Unfortunately, there are just too many possibilities from that area of the world for me to hazard a better guess. I seriously doubt that any obligate myiasis is involved here. Hope this helps. Tim. Dr. Randolph again: In case we are dealing with something not larval, like a roundworm, the thing is going to be there a long, long time. Keeping the wound clean, at least daily, will be crucial. Is there any possibility that you could travel to a nearby country with better veterinary care? In the worldwide information scene many of our professional journal articles come from Israel, so I would have confidence in visiting a doctor there, especially if you could obtain a referral to a veterinary teaching hospital. Please keep us informed. I know all of our readers will be on the edge of their seats to know what happens next!

    • Varn-emily90458 13 June 2014 at 1:10 pm #

      How do you clean the area after it comes out? How long should it take to develop?

      • Dr. James W. Randolph 13 June 2014 at 10:00 pm #

        Hi, Emily. My biggest worry after removing the larva is infection. Keep the area clean with hydrogen peroxide, but if pus develops or your pet has a fever or loses its appetite, be sure to see your local veterinarian right away. It is impossible to say how long a given larva will develop because we don’t know when it first arrived. However, you can read the article again for an explanation of the life cycle. We know that once the larva arrives under the skin it resides there about a month before leaving.

  17. Mark Youhana 4 July 2010 at 10:27 am #

    Thanks for that useful information. I really need some help. I am from Egypt and veterinarians are not that good, so I am afraid to take my infected cat to any of them. What if I left the cat to expel that foreign body out, is there any danger?? PLZ respond ASAP

    • Dr. James W. Randolph 5 July 2010 at 4:01 pm #

      Mark, this is a tricky question. If biology follows its natural course the larva will pupate, then hatch into a fly. If all of those steps go “normally,” AND your kitty doesn’t become infected, she’ll be fine. However, if the larva isn’t able to escape, if you’ve misdiagnosed and there isn’t a Cuterebra larva in there (and, instead, it’s tumor or bite wound), then you could have some serious difficulties. It’s a tough spot to be in: going to the doctor might be worse than NOT going to the doctor. I’d have to guess that your best course of action would be to watch it a few days and if her activity level and appetite get worse then you’d have no choice but to take her to see the doctor. Please let us know what happens, we’re on the edge of our seats! Best wishes,
      Dr. Randolph

  18. Nell 19 May 2010 at 11:34 am #

    Good for me, I keep my cat indoors. We don’t have fleas or ticks either.


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