Quick and Effective Ways to Treat Bot Flies in Cats

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Bot flies are a type of parasitic insect that can affect various animals, including cats.

Although it is relatively rare for cats to be infested by bot flies, it’s crucial for pet owners to be aware of the signs and know what to do if their feline companion encounters these pests.

One common species of bot fly, Cuterebra fontinella, is found in most of the continental US, southern Canada, and northeastern Mexico.

This large, robust fly can cause issues for cats if its larvae infest their skin, leading to a condition called “cuterebriasis.”

Botfly Laying Eggs
Botfly Laying Eggs

To prevent bot fly infestations in cats, it’s essential to take certain precautions like keeping them indoors, checking for and promptly removing any ticks, and using veterinarian-recommended preventive measures.

Additionally, consult your vet immediately if you suspect your cat has been affected by bot flies, as they can provide appropriate treatment and advice.

Bot Flies in Cats: Causes and Life Cycle

Life Cycle and Host Animals

Botflies, specifically the Cuterebra fontinella, are found in North America and can infect a variety of mammals, including cats and dogs.

The life cycle of botflies includes four stages: egg, larva, pupa, and adult.

Adult botflies are non-biting flies and lay their eggs near rodent burrows or in grass, attracting host animals.

Rodents and Rabbits as a Source

Rodents and rabbits play a significant role in the life cycle of botflies.

When a cat preys on an infected rodent or rabbit, they may accidentally ingest or come into contact with botfly eggs.

Bot Flies in Cats
Immature Rodent Botfly

The eggs hatch into larvae, which then burrow into the cat’s skin, typically around the face, neck, or head.

Cats may also encounter botfly eggs in grassy areas or while exploring outdoors, the eggs stick to their fur and eventually hatch into larvae that burrow into their skin.

The burrowed location forms a lump, called a warble, where the larva develops before exiting the host and maturing into an adult.

Host Animal Infection Source
Cats Preying on rodents, rabbits, or outdoors exposure
Rodents Housing botfly larvae or eggs
Rabbits Same as rodents, hosting larvae or eggs

Botfly Infestation Effects:

  • Lump or warble formation
  • Possible infection if untreated
  • Irritation and discomfort for the host

Important Prevention Tips:

  • Monitor your cat’s outdoor activities
  • Treat rodent and rabbit populations around your home
  • Regularly inspect your cat for signs of infestation

If you notice a lump or suspect a botfly infestation on your cat, consult a veterinarian immediately.

They can remove the larva and treat any infection, ensuring your cat’s health and well-being.

Symptoms and Identification of Botfly Infestation

Lesions, Swelling, and Warbles

When a cat is infested with bot flies, the skin may exhibit various signs. Lesions on the cat’s skin can be an indication of a bot fly infestation.

Moreover, a noticeable lump or swelling around the lesion site is a common symptom.

This swelling is called a warble, caused by the larvae living just under the skin. These warbles are usually found on the face and neck.

Botfly Larva
Botfly Larva

Respiratory and Neurological Symptoms

Apart from skin symptoms, cats may also experience respiratory and neurological issues due to bot fly infestation. Respiratory issues can include:

  • Sneezing
  • Nasal discharge
  • Coughing
  • Gagging

Neurological symptoms are more severe, and they include:

  • Circling
  • Head tilt
  • Seizures
  • Lethargy
  • Lack of appetite
  • Excessive grooming
  • Paralysis
  • Abnormal behavior

In some cases, cat infested with bot flies may even suffer from blindness, cyst formations, or bacterial infections. An allergic reaction or anaphylaxis could also occur, though rare.

Symptoms Infested with Bot Flies Infested with Ticks
Lesions Yes Yes
Swelling Yes Yes
Warble Yes No
Respiratory Yes Some varieties
Neurological Yes Lyme disease or other tick-borne diseases
Anaphylaxis Rare Rare

It is essential to identify these signs for early intervention and treatment. It’s important to differentiate bot fly infestation from similar issues like tick infestations, as the treatment methods differ.

Always seek a veterinarian’s help when addressing your cat’s health concerns.

Diagnosis and Treatment

Veterinarian Consultation

If you suspect your cat has a botfly infestation, immediately consult your veterinarian.

They may perform a physical examination and potentially order a CT scan to identify the location and severity of the infestation.

Surgical Removal

In some cases, surgery is the recommended method for botfly removal in cats. Your veterinarian will administer anesthetic and make an incision in the lesion to extract the botfly larvae.

Surgical removal ensures the entire larvae is removed without causing further harm to your cat.

USGS Bee Inventory and Monitoring Lab, Public domain, via Wikimedia Commons

Source: USGS Bee Inventory and Monitoring Lab, Public domain, via Wikimedia Commons

Pros of Surgical Removal:

  • Complete removal of larvae
  • Lowest risk of complications

Cons of Surgical Removal:

  • Expensive
  • Invasive procedure
  • Recovery time post-surgery


An alternative treatment option is manual extraction. Your veterinarian may use forceps to carefully remove the botfly larvae from the affected area.

They may administer corticosteroids or antiparasitic medications to reduce swelling and prevent infection.

Pros of Extraction:

  • Less invasive
  • Lower cost compared to surgery

Cons of Extraction:

  • Incomplete removal risk
  • Potential for complications
Treatment Method Pros Cons
Veterinarian Consultation Accurate diagnosis; Professional treatment recommendations; Proper follow-up care Costly; Time-consuming appointments
Surgical Removal Complete removal of larvae; Lowest risk of complications Expensive; Invasive procedure; Recovery time post-surgery
Extraction Less invasive; Lower cost compared to surgery Incomplete removal risk; Potential for complications

Regardless of the method chosen, prompt treatment is essential for the animal’s overall health and well-being.

A good prognosis and minimal blood loss can be expected when treatment is timely and handled by a professional.

Prevention and Aftercare

Outdoors and Pet Interaction

Preventing bot fly infestation in cats involves reducing their exposure to the outdoors, where they may come across infested rodents or rabbits. Examples of preventive measures include:

  • Keeping your cat indoors as much as possible
  • Supervising their outdoor activities
  • Pest control to keep rodent populations down

Another preventive measure is regular checks of your cat for any signs of myiasis, such as small lumps or wounds on their skin.

In case you own horses, monitor them too, as they can be infested by warble flies, a type of bot fly.

Antibiotics and Recovery

In case your cat is infested with bot flies, seeking prompt treatment from a veterinarian is crucial.

The veterinarian will carefully remove the parasitic larva and clean the wound. This process may involve:

  • Sedation for the removal procedure
  • Gently squeezing the larva out
  • Antiseptic cleaning of the wound

After larva removal, follow-up care is essential to ensure your cat’s recovery. It may involve:

  • Administering antibiotics to prevent secondary infections
  • Regularly cleaning the wound as advised by the veterinarian
  • Ensuring proper nutrition and hydration for your cat’s recovery
Method Pros Cons
Keeping your cat indoors Reduces exposure to bot flies and infested animals May cause boredom or stress in some cats
Supervising outdoor activities Allows you to monitor your cat’s interactions with animals Time-consuming
Pest control Helps reduce rodent and rabbit populations May involve the use of toxic substances

By combining these prevention and recovery steps, you can protect your cat from the potential harm caused by bot flies, particularly in North America, where the problem is widespread.


Bot flies, particularly the Cuterebra fontinella species, pose a potential threat to cats in North America.

While infestations are relatively rare, the consequences can be severe, leading to conditions like cuterebriasis.

Recognizing the symptoms, such as skin lesions and respiratory issues, is crucial for early intervention.

Treatment options range from surgical removal to manual extraction.

Preventive measures, including keeping cats indoors and regular health checks, are essential for safeguarding our feline companions from these parasitic pests.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about bot flies. Scroll down to have a look at some of them.

Letter 1 – Bot Fly Pupa

Subject: Bug
Location: Florence, Mississippi
December 12, 2015 8:29 am
I found this bug in my house along with my dogs. I am concerned that it is some sort of parasite, but was not able to identify it yet. If you know what this is it would surely ease my mind and worrying.
Signature: In waiting Jamie Hancock

Rodent Bot Fly Pupa
Rodent Bot Fly Pupa

Dear Keith,
We believe this is a Rodent Bot Fly Pupa, an internal parasite that is usually very host specific.  Since you found it in the home, we are surmising the host may have been a mouse or rat.

Rodent Bot Fly Pupa
Rodent Bot Fly Pupa

Letter 2 – Bot Fly Metamorphosis

What’s this bug?
First of all, Great Site! My daughter has a biology project coming up soon and I am sure she will find this sight handy. My kids and I always seem to be hatching something in a jar. Well, this was our latest surprise. My boys found the cocoon in the dirt in our back yard.

So we stuck it in a jar with some dirt. A few days later they found a different cocoon and added it to the jar and there they sat. First inside, then outside for a while and then back inside. One hatched within in a month or so, some sort of moth.

We thought the other one didn’t make it since it had been a few months and there was no sign of life. Then one night my son yelled to me that we had a new family member. That’s what we call them, family members.

So, with every new family member comes family photos. Our album is becoming quite extensive. This one was not familiar so I didn’t let them hold it, thought it could bite or sting. We searched through our Audubon Society bug book but couldn’t find anything.

So I started looking on line and your site has been wonderful but I still can’t find what it is. Is it a Fly or what? Please tell us more…
Riverside, CA

Hi Nancy,
We just ran a letter concerning a Bot Fly about a week ago, but we only had the pupa and no adult photo. Your photo is the first we have received of an adult Bot Fly or Warble Fly, Family Oestridae. The Larvae are endoparasites of various mammals, most notably rodents like squirrels or rats.

Other species are parasitic on deer and a human Bot Fly can be found in Central America. The female fly lays eggs where the host will come into contact with them, and the eggs hatch almost immediately due to the warmth of the hosts body. The larvae then enter the hosts body usually through an orifice and then form fleshy warbles with holes to allow the larva to breath.

Thanks for your wonderful contribution. Eric Eaton just provided us with the following information: ” Neat that the bot fly hatched! It is one in the genus Cuterebra, which are rodent and rabbit bots (each species prefers either rodents or rabbits). The adults do not feed, in fact have no mouthparts! Really cool, rarely seen….”

Letter 3 – Bot Fly laying Eggs

Subject: bug mystery in quebec
Location: my yard, near montreal and quebec city, quebec, canada
July 19, 2015 3:45 pm
hi there bugman. found a bug, couldn’t identify it, we’re curious if you can help us. it was pooping white/transparent goop, head upside down in the grasses of my yard. location: southern quebec, canada.
Signature: s+r

Rodent Bot Fly Ovipositing
Bot Fly Ovipositing

Dear s+r,
You images are a thrilling addition to our archives.  This is a female Bot Fly in the genus
Cuterebra, and she appears to be in the process of laying eggs, the “white/transparent goop” that you observed. 

Rodent Bot Flies are parasites of rabbits, mice, squirrels and other rodents.  According to BugGuide:  “Females typically deposit eggs in the burrows and “runs” of rodent or rabbit hosts. A warm body passing by the eggs causes them to hatch almost instantly and the larvae glom onto the host.

The larvae are subcutaneous (under the skin) parasites of the host. Their presence is easily detected as a tumor-like bulge, often in the throat or neck or flanks of the host.

The larvae breathe by everting the anal spiracles out a hole (so they are oriented head-down inside the host). They feed on the flesh of the host, but only rarely does the host die as a result.”

Rodent Bot Fly Ovipositing
Bot Fly Ovipositing

Jeff Boetner, Bot Fly expert, provides some information.
Hi Daniel,
Nice pics. This is a relative of your mystery FL bot from a week or so ago. But this one we can ID as Cuterebra fontinella fontinella. This is a nice shot of a freshly emerged female. The fontinella bots are known for the white rumps on the last segment of the rear end.

This is a huge female, they can lay over 1,000 eggs in their short lives. Most eggs are laid in mouse runways or near burrows. The fluid you saw was likely because the female just emerged from her pupae (in the soil). Bots have no mouth parts or digestive tract so no need to poop.

They have to store up all their energy they need as adults, by feeding as a maggot in the mouse host, and this one did a good job of that, judging by her big body size. This one is a specialist on white-footed mice, Peromyscus leucopus.

This species is our most common bot, yet not found as often as you would think. I have trapped over 200 mice per hectare*. in our plots in MA, and sometimes 80% will have 1-2 bots, so you would think there would be huge numbers out there.

And yet many entomologists I have met, have never seen one in the wild. So consider yourself lucky…(or unlucky if you are a white-footed mouse).

*a hectare is approximately 2 1/2 acres.

Thanks a lot for the quick answer, dude/dudette(s)! We weren’t expecting close to this quick of a response. I’ll be sure to bug you again for some more IDs (hohoho).

Letter 4 – Immature Bot Fly

Subject:  Should I be worried?
Geographic location of the bug:  Eugene, OR
Date: 12/01/2017
Time: 04:02 AM EDT
I found three of these really gross larva inside my house this week, November 2017. Based on internet searches, I think this may be a bot fly larva. We have cats which like to bring us “mice” presents which are not always dead.

These larva were found in the room where I had caught the mouse the day before. If you kill the mouse would the larva try to leave the body or should I be looking closely on the cats assuming this a bot fly larva?

How you want your letter signed:  Grossed-Out Becky

Immature Bot Fly

Dear Grossed-Out Becky,
We concur that this is an immature Bot Fly.  Rodents are typical hosts, but we believe we have read that rarely a domesticated pet may also act as a host

Thank you for your quick response.  I’m checking my cats just in case.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Mystery: What’s Growing on the Dead Rat???

Pupal case embedded in decaying rat?
June 1, 2010
Hello! I have long loved your website and need your help! This large, hive-shaped brown growth is emerging from the throat of a large brown rat my cat killed. You may be able to see the significant maggot population under the forearm, but the corpse is still intact for the most part. It appears larger than most of the fly pupae I have found descriptions of on the internet. Can you help? I am very curious – almost mistook it for a cancerous growth! Thank you!!
W. Barker, huge fan!
Sierra mountains, Northern CA

Thing on a Dead Rat

Dear W. Barker,
If we had just read your letter and there was no photo, we would have argued that the creature was a Rodent Botfly in the genus Cuterebra, but the thing on your dead rat looks nothing like the Rodent Botfly Larva pictured on BugGuide.  We are going to post your letter and photos and request assistance from our readership.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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Tags: Bot Fly

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7 Comments. Leave new

  • Thrilled to have earned a spot on your site! I have additional photos (w/tape measure for comparison) and can send them if you are interested. The end of the pupal case (?) has gone from circular with clear liquid inside to flat – perhaps because I manipulated it gently? The rat is an 8″ Norway Rat and the embedded case is very large – 3/4″ to an inch across. Thanks again!

  • Actually, I think you were right with the original assumption of this being a rodent botfly… Check out the photos on this documentary http://www.fcla.edu/FlaEnt/fe91p706.pdf I am not sure of the exact botfly that this would be, but I think you were all in the correct area.

  • One last detail: while the shape is nearly identical to that of the botfly pupa, it is smooth – none of the bristles shown on all botfly pupal cases I have seen so far.

  • Suzanne Garofalo
    August 13, 2013 10:28 pm

    My cat killed some kind of medium size rodent and left it for me to find in the driveway – he is vocal about his kills so I found it with in minutes – and by that time two large – say about 1 inch long and 1/2 inch wide brown “things” were making their way to the carcass – they really gave me the willies. I scooped up the lot and tossed it well over the fence in to a fallow field adjacent to my property.

    Two nights later, cat kills another rodent. I get to it before any creepy crawlies appear and toss this one into a dense shrub (thinking cat can’t get to it). The next morning the cat brings me the rodent again and TWO of those nasty things have burrowed into its lower belly close to its haunches -one on either side.

    I started reading the above mentioned article on Bot flies but stopped when it described the larvae exiting the dead rodent as the bugs I am looking for info on appear to have attached themselves after death.

    WHAT ARE THEY??? I wish I’d never seen them!

  • This morning my cat caught a rat and brought it into the house for me. It was still alive and I didn’t have time to deal with it before work so I managed to get it into my enclosed shower and closed it in until after work. When I got home tonight it was dead and a large dark brown wiggly larva thing exactly as you described had exited through the rats groin area. It was alive and still near the rat. I flushed it but am also wondering what it was. Ewwwww

  • I hope all of you who let your cats out and kill thing are regularly getting your cats wormed. (keep em in and give them an enclosed porch…better for everyone )


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