Reviewed by Sara Ochoa, DVM
October 30, 2022
Does your dog love to dig in the dirt? Most dogs do! They also love to run in fields, stick their noses in rodent burrows, and investigate dark and smelly places outside.
Dogs seem to be living their best lives when engaged in these activities.
Unfortunately, there may be a price to pay if there happens to be botfly larvae nearby.
If your dog’s nose is close, it can enter the dog’s nasal cavity. From there, they can settle under your dog’s skin, in the respiratory tract, or even (rarely) in the brain.
There are certain symptoms to look for in a dog with warbles. There are also specific ways to treat warbles.
Dog owners are tempted to remove the small worms from beneath the skin themselves. This, however, is not advised.
Want to know why you can’t do it at home?
Keep reading to learn about the serious risk of bacterial infection caused by DIY worm removal.
We’ll tell you which bot flies cause serious risks, where their larvae can be found, signs, symptoms, and appropriate treatment options for your dog.
A Little Bit About the Botfly
It’s common for dogs to contract a variety of external parasites, especially if they are not treated with regular anti-parasitic treatments.
We’ve all heard of fleas, lice, and ticks. Most pets are likely to have encountered any of these parasites in their lifetime. However, dogs from Central and South America face different risks.
Have you rescued a dog from Central or South America? If so, your dog may have something called warbles.
Warbles in dogs (known as a Cuterebra infection) is caused by the larvae of bot flies.
There are actually 34 species of Cuterebra in the world and most are uncommon in North America. Rodents are infected by 12 of those species. The remaining 22 species infect rabbits and hares.
Most species of bot fly cause no problems for humans or pets. However, the rabbit bot fly (or rabbit Cuterebra) has been known to cause serious health problems in infected dogs and cats.
How Could My Dog Be Infected with Warbles?
As early as 2018, bot flies were considered rare in North America.
Now, according to wording in the Oxford Academic Journal of Medical Entomology, the larvae of these large flies are beginning to show up in the United States.
My point is, while still considered “rare”, it seems increasingly possible for dogs to become infected. Rising temperatures have upended normal seasonal changes leaving dogs and humans more at risk of contracting warbles.
Life Cycle of the Cuterebra or Botfly
Adult Cuterebra flies deposit their eggs around the openings of rodent and rabbit burrows, around long blades of grass, or in nests.
Once they hatch, the botfly larvae usually infect the rabbits and rodents nearby. However, if your dog has his/her nose down in the hole, the larvae could infect him.
It takes a few days for the larvae to make their way to the tissues beneath the skin.
Where Dogs Pick Up Parasitic Larva
Female botflies tend to lay their eggs in places where dogs like to romp (parks, hiking trails, in the woods while camping, etc.).
Sometimes the botfly will deposit her eggs underside of a tick or mosquito.
The eggs stay there until they sense the warmth of an animal. The egg hatches into maggots and drop off onto the animal passing by.
When your dog sticks his face down there for a sniff, the larvae can enter through the dog’s nose, mouth, or even through a skin wound.
The warm tissue of mammals serves as a great incubator. Botfly larvae need the body heat of mammalian hosts to mature.
In fact, most cases of warbles in dogs are found around the head and neck.
What Are the Symptoms of Warbles in Dogs?
In the early stages of an infection, you may not notice anything different about your dog. It’ s only after the maturing pupa begin to squirm around that you spot the problem.
The dogs skin is a prime place to find these infestations.
They may look like a type of pimple or cyst at first. If you look closely, you can see movement under the skin and a small hole for breathing.
If you leave it alone, the pupa will reach maturity within 3 – 6 weeks and fall out on its own. Once it drops to the ground (soil) it will develop into an adult fly.
If this happens, the hole that is left in the skin needs to be disinfected and kept clean to prevent bacterial infection.
Prime egg-laying seasons is in the late summer and early fall. Signs of a botfly infestation include:
- -hard, raised skin lesions
- -pain when touched
- -swelling around the area
- -hive-like rash
- -red, pink, or purple raised skin
If your dog has a large infestation, he/she may experience lethargy, lack of appetite and vomiting.
Are Warbles in Dogs Dangerous?
In rare cases, warbles can have a significant impact on a dog’s health.
Depending on the affected area, warbles can cause problems in the upper respiratory tract, eyes, and in the central nervous system. Neurological signs include:
- -unsteady or wobbly gait (ataxia)
- -head pressing
- -head tilting
- -low body temperature
- -odd behavior
If your experiences head pressing, head tilting or spinning in circles for no reason, he/she needs to get to a vet ASAP. This is likely a medical emergency.
Treating Warbles in Dogs
A licensed veterinarian can manually remove warbles from an affected animal.
If there are neurologic signs or respiratory signs of warbles, it becomes a little more complicated. In that case, the dog will require surgery so that the veterinarian can access and remove the larvae.
The Risks of DIY Removal
It’s always a good idea to have a veterinarian remove the warbles from your dog’s skin.
They have equipment that has been disinfected. They’re also skilled at how to do this without squeezing the larvae.
If you try to remove larvae yourself, you may accidentally squeeze them.
It doesn’t take much for them to leave a bit of discharge behind. Any residue left behind can cause serious bacterial infections and more pain for your dog.
In addition, your dog’s skin tissue will already be compromised. It won’t take much for you to cause further injury.
It’s always best to allow a licensed veterinarian do the job.
5 Things Your Dog Can’t Tell You About Warbles
There are a few things about warbles in dogs that you may not realize.
As the larva grow, they develop spines that dig further into the tissue and cause pain.
They’re Not Contagious
You can’t “catch” warbles by touching the larvae or coming in contact with an animal who is infected.
Secondary Infections Are More Dangerous
Even if the larvae has emerged and fallen from the skin, the remaining cyst needs to be thoroughly cleaned and treated to prevent bacterial infection.
Warbles Can Migrate Near Nerves, Tissues, or Organs
Sometimes (rarely) warbles can find their way to dangerous territory in your dog’s body. If this happens, surgery may be too tricky or dangerous to completely remove the larvae.
Warbles that cause central nervous system complications are much harder to treat.
If surgery doesn’t work, the affected dog may be treated with ivermectin, antihistamines, anticonvulsants, and a tapering dose of glucocorticoids.
Your Dog Can Still Go Out and Play
Try to prevent further infestations by keeping your dog away from burrows and other areas where larvae may be hiding.
That said, you can still bring your dog to the dog park, on a run, or for a walk as per his/her usual routine.
Words of Advice
Finding warbles on dogs is gross. There’s no other way to say it. However, it might be helpful to know that they can’t directly hurt you.
Getting them out of your dog is the top priority because they cause pain and can create secondary infections.
If you have a hunting dog, or a dog that’s able to run in wide-open spaces, near farms, in the fields, etc., it’s a good idea to do daily checks.
There are a lot of parasites in the natural environment. Ticks are very common and can cause Lyme disease (as one example).
Check your dog’s head and neck first. Look in the ears, within the folds of the ears, along the top of the head and down the neck.
Use a combination of touch and sight to detect parasites. Ticks are often very hard to see until they latch.
Bone Up on Parasite Info
Parasites are nasty, but it’s important for dog owners like us to understand where dogs get them and the problems they can cause.
For this reason, I’ve hand-picked a few posts that might prove useful to you. Check these out:
Your Ultimate Guide to Hookworms in Dogs
9 Clinical Reasons Why Dogs Shake Their Heads
23 Things You Need to Know About Lyme Disease in Dogs
Why it’s Critical to Stop the Heartworm Life Cycle in Dogs
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Kelowna Veterinary Hospital Ltd – The Botfly
Wiley Online Library
Journal of Veterinary Emergency and Critical Care Case Report
FirstVet – Common Health Concerns