Finding maggots in a pet’s wound, or a swelling with a small hole in it, is upsetting. Both are caused by fly larvae, and both need a vet. This guide covers the two main forms seen in dogs and cats: fly strike (myiasis) in wounds and Cuterebra (bot fly) warbles under the skin.
Fly strike (myiasis): maggots in a wound
Myiasis is the name for an infestation of skin or other tissue by fly larvae (maggots). In everyday speech it is often called fly strike. [1][3]
How it starts
Most cases in dogs and cats in the U.S. involve common flies such as house flies, blow flies, bottle flies and flesh flies. These flies need something to draw the female to lay her eggs: damaged skin, a neglected wound, discharge from the eyes or another body opening, or a coat soiled with urine or feces. [1] Typical risk situations include:
- Wounds from fights or bites, a common starting point in cats that roam [3]
- Neglected newborn kittens, where infestations of the umbilical area, the ears and the anal region have been reported [3]
- Matted or soiled coats, including pets that cannot groom normally because of obesity or illness [1][3]
The larvae feed on discharge and dead tissue in the wound. Even when they do not eat healthy tissue, they irritate the wound and keep it weeping. [1]
What it looks like
You may see larvae under matted hair or in a wound, sometimes with small punched out holes in the skin, and there is often a foul smell. [1]
Leave the maggots to your vet
Do not try to pick out maggots at home. Treatment is a veterinary job: the vet clips away hair and mats, removes the larvae, cleans the wound, removes dead tissue if needed and treats any infection. Some types of myiasis also need medicine from your vet. [1] Larvae can be hidden in tunnels under the skin, and more than one kind of fly can be involved. [1][3]
In a study of a Greek dog shelter, 7 of 163 dogs developed myiasis over 3.5 years (two of them twice, in different body areas). Sites included the thigh, the ear canal, the prepuce, the toes and the vagina. Treatment included removal of the larvae, cleaning of the area and medicines given by the vets, and complete recovery was achieved within 1.5 months, except for infestations of the prepuce, which took 2.5 months. [4]
Cuterebra warbles (bot fly larvae)
What they are
Adult Cuterebra flies are large and look like bees. They neither bite nor feed. Females lay their eggs along rabbit trails and near rodent burrows, and when a dog or cat brushes against the eggs they hatch and the larva gets into the body. Rabbits and rodents are the usual hosts, so dogs and cats are accidental ones. [2] Cats that roam in areas with these flies are more likely to pick them up. [3]
What they look like
Swellings usually show up in late summer or fall. [2] Look for:
- A lump about 1 to 2 centimeters (roughly half an inch to three quarters of an inch) across [2]
- A small breathing hole in the middle of the lump, through which part of the dark larva may be visible [2]
- Lumps mostly on the head, neck and trunk [2][3]
Do not squeeze a warble
Your vet confirms a warble by widening the hole and seeing the larva, then lifts it out carefully. The larva needs to come out in one piece, because parts left behind can cause an allergic or irritant reaction. Squeezing it yourself risks exactly that. Afterwards the wound is kept clean, and healing is often slow. [2]
When larvae go deeper
Because dogs and cats are not the fly’s normal hosts, the larva sometimes wanders to the brain, the throat, the nose or the eyelids. [2] In cats, a larva in the nose or airway can cause sneezing, nasal discharge or breathing trouble, and a larva in the brain can cause signs such as blindness, circling, a head tilt and seizures. A review of cases in cats found that brain infestation was usually fatal. [3]
A review of 42 cases (22 cats and 20 dogs) found that Cuterebra infection can cause severe whole-body illness in small-breed dogs. Most of the affected dogs (16 of 20) weighed 10 lb (4.5 kg) or less, Yorkshire Terriers were overrepresented (8 of 20), and 6 of the 20 dogs and 1 of the 22 cats died. [5]
Helping prevent fly strike
- Have wounds and skin sores checked by your vet, and follow your vet’s advice for keeping them clean while they heal. [1]
- Keep the coat clean and free of mats so urine or feces do not build up on the skin, especially in older, overweight or ill pets that struggle to groom. [1][3]
- Keep a pet with a healing wound away from flies, indoors or in a screened area if possible. [1]
When to see your vet
Go to your vet promptly if your pet has:
- Maggots in a wound, sore or the coat
- A swelling with a small hole in it, especially on the head, neck or body in summer or fall
- A wound that oozes or is not healing
- Sudden violent sneezing, walking in circles, blindness, seizures or a change in mental state, especially in a cat that roams outdoors
FAQ
Can I pull the maggots out myself?
No. Your vet needs to clip the area, remove all the larvae and clean the wound, and some cases need medicine as well. [1]
Can I squeeze out a warble like a pimple?
No. The larva has to come out whole, and pieces left behind can cause an allergic or irritant reaction. [2]
Why does my vet want to see my pet again?
Larvae can hide in tunnels in the tissue, and the wound needs to stay clean and fly-free until it heals. [1]
Are indoor cats at risk of warbles?
The risk is mainly for cats that roam where rabbits and rodents live, since that is where the fly lays its eggs. [2][3]
The bottom line
Maggots in a wound and warbles under the skin are both fly larvae, and both are a job for your vet: do not pull out maggots or squeeze a warble. Have wounds checked early, keep the coat clean and free of mats, and keep a pet with a healing wound away from flies.
This article is for general information and is not a substitute for veterinary advice. If you see maggots or a warble on your pet, please see your veterinarian promptly.
Sources
- Torres SMF. 3.18 Myiasis: Small Animals. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota Libraries Publishing, 2025 (CC BY 4.0). https://open.lib.umn.edu/animaldermatology/chapter/miyasis-small-animals/
- Torres SMF. 3.21 Cuterebriasis: Small Animals. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota Libraries Publishing, 2025 (CC BY 4.0). https://open.lib.umn.edu/animaldermatology/chapter/cuterebriasis-small-animals/
- Pezzi M, Bonacci T, Leis M, Mamolini E, Marchetti MG, Krčmar S, et al. Myiasis in domestic cats: a global review. Parasit Vectors. 2019;12(1):372 (CC BY 4.0). PMC6664729. https://pmc.ncbi.nlm.nih.gov/articles/PMC6664729/
- Orfanou DC, Papadopoulos E, Cripps PJ, Athanasiou LV, Fthenakis GC. Myiasis in a dog shelter in Greece: epidemiological and clinical features and therapeutic considerations. Vet Parasitol. 2011;181(2-4):374-378. PMID 21536388. https://pubmed.ncbi.nlm.nih.gov/21536388/
- Rutland BE, Byl KM, Hydeskov HB, Miniter B, Johnson CA. Systemic manifestations of Cuterebra infection in dogs and cats: 42 cases (2000-2014). J Am Vet Med Assoc. 2017;251(12):1432-1438. PMID 29190191. https://pubmed.ncbi.nlm.nih.gov/29190191/