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.

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  1. My cat loves me very very much and just brought me a large rat that was infested with Bot fly larvae and rat lice. YUCK! Can any diseases from the larvae and/or lice be transferred to my cat?

  2. i found a kitten it was near death my wife nursed it back to good health or so we thought her head bobs up n down and her legs wont support her she launcges her self with her rear legs to go any where but she is playfull and has a great appeitite my wife hast hold her so her head wont fall in the food

  3. my mini schnauzer was recently diagnosed with kennel cough, then graduated to a collapsed lung and in the meantime got several cysts under her skin- i asked about them and the first vet said its probally clogged oil glands – but when her breathing got bad again today, i took her back to my local vet and i asked again about the bumps where he looked at them and extracted 6 different places of larva- Cutebra . He is contacting a specialist as he hasnt seen it on may animals here in utah- and how to deal with it. My pup still has a lung partially collapsed, could the larva be infested in the lung for air rather than coming to the surface? she is only 1 year 6 months old- and been to the vet for the cough, lung now larva……… shes finished her antibiotics, steriods, xrays- and now this larva thing– im about to loose my marbles.. i just want my furbaby better–

    • Cuterebra wouldn’t have migrated to the lung for air, but the larvae are known to migrate to aberrant locations. I’ve heard of them being in nasal passages and the central nervous system. You may need a specialist for that lung. Does she have a chest tube? Best wishes, Dr. Randolph.

  4. A week and a half ago, my Lhasapoo had a botfly larvae removed from her back. Four days later, I found another behind her ear. Between the two visits to the vet, I did a lot of research online and had some questions for the vet. Unfortunately, I knew more than she did at that point, and she pulled out her phone to look up the information I was giving her. I’m trying to weed through the information I found online and would love some help, either in the form of answers you might be able to provide, or a recommendation to someone who might know more. First, I have seen some conflicting information on how the warble forms. Some sites say the eggs get into an opening, traveling under the skin, then bore out. Other sites say the eggs live in the fur, then bore down. Second, I saw one site that said that once a dog is infected, the larvae can live inside of them for 2 – 3 years. Is this accurate? I’m also concerned that no other dog in our neighborhood has had a problem with botflies. I live in a condo complex with a lot of dogs, but mine seems to be the only one who has been infected. I’m wondering if there is something that either of us are doing that might make her more vulnerable. She walks in the same areas as the other dogs, and plays in the same grass, but none of them have had a problem. She does lick herself quite a bit – especially her paws, so if the larvae do form by entering the mouth, she might be more likely to infect herself by licking. Finally, in order to help me figure out how (or where) she became infected, I am wondering how long it takes from the time they are infected to the time a warble forms. We live in Denver, in case different areas have different types of botflies. Thank you!

    • Step One is to get one or more of the extracted larvae to a veterinary parasitologist for identification. Each larval species has a different life cycle. Treatment and prevention can then be tailored specifically. Your veterinarian can submit the specimen(s) for you. Best wishes, Dr. Randolph.

    • I Live in CO as and my dog went to the vet today. She told us that the cuterebra had already left my dogs body. When he was sitting in my lap this evening. I could clearly see a worm like creature popping its head out of the whole every fews seconds to come up for what seemed like air.

  5. My family was just given a 9 week old kitten from a family friend and today I found that she had 2 Cuterebra one on her neck area and the other on her left cheek. I was very successful in removing the one from her neck however when i was removing the one from her cheek she moved and it slipped from my tweezers slightly and tore but never went fully back into the hole. I got my grip on it again and removed the whole thing put rubbing alcohol on the hole and she seemed fine. I went back to check on her about a half hour later and the area under her chin is swollen. We do not have the money to take her to the vet and I can not lose her or my babies will be very heartbroken they are already very attached to her even though we have only had her a week. Is there anything I can do for her at home?

  6. My daughter found a kitten out in the country and brought it home to me yesterday as a Mothers Day present. There was what she thought was a puncture mark from perhaps another kitten. It turned out to be a cuterebra. I was able to remove the larva without rupturing it, irrigated the hole it came out of. There is no puss present but a bit of a knot where the thing had been under the skin. Is amoxicillin a viable treatment for aftercare as I am not able to get her to the vet?

  7. we noticed a red lump on my dog’s skin and we left it for some time to go down but we noticed it became really disgusting and we started pulling out larvae from the lumps. please I want to know how I can treat her, I’m really worried about her. she is as crazy as usual and she eats well too but I don’t want those disgusting things on her skin. please what can I do about it

  8. I noticed a lump on my cat’s neck about a month ago. It’s not painful, and after researching on the internet possible infections, I came to suspect that is was either a benign cyst or possibly a botfly infection. The latter would make sense, since around last fall, I had small red bot flies flying around my apartment (I didn’t know they were or that they could cause botfly infections in animals. I’m also not sure how I got a minor botfly infestation, except that I had had, this past summer, two outdoor dogs in my home and the former dog had given me a minor mite problem, as well. I had also used my cat’s brush to brush his coat, unfortunately.)
    I noticed after a couple weeks after discovering the small lump on my cat’s neck, that some black substance was being excreted from a small hole that I was not there before. I took tweezer and gently pulled out the black substance and it didn’t appear in any way to be a living creature, more like some kind of black substance. More would reappear after several days and I would keep removing it.
    I never once seen any type of parasite moving around or poking its head out of the hole that is on the lump. Every time I would be examining the lump, my cat never displayed any signs of discomfort, concerning pain.
    Today, I noticed some more of the black substance coming out of the hole on the lump and after I removed it, I gently squeezed the area around the lump and I felt kind of a bit of a pop and pus came out of the lump. My cat still didn’t seem to be in any pain and I had made sure all the pus was squeezed out and then I had washed the wound with soap and water.
    I can’t afford to take her to the vet, however there is a foundation that will help me financially to be able to take her. I will be calling them tomorrow morning.
    Can you please let me know if this sounds serious? I am very worried, as I have read that some people had lost their pets due to botfly infection.

    • Black stuff, eh? This is going to take some hands-on, eyes-on examination to know what’s going on. However, it doesn’t sound like anything that’s going to go from starting a month ago to fatal before Monday, most likely. Do, please, let us know what your veterinarian finds out. I’ll be on the edge of my seat. We’ll say a prayer for a good outcome. Thanks for reading http://www.MyPetsDoctor.com.

      • Yes, black stuff being excreted out of the hole on the lump. I was suspecting that it was perhaps the feces from the possible parasite.
        Other than that, my cat, Halo, hasn’t shown any other signs or symptoms of abnormal behavior.
        Thank you for your website and for your response, I really appreciate it! Thank you for the prayer, it means a lot, and yes, I will let you know what the vet finds out.

  9. I have three beagle hound mixes all with multiple lumps that have appeared in last several months. We have found rat with larvee (they came out as it died), we also have squirrels. My dogs have been to vet and diagnosis is fatty tumors. They are taking Ivermectin for heart worms. Could it be possible for larvee to grow and die between monthly dosage? Would the larvee just disintegrate? Or have they just grown alot of new tumors?