Understanding Botfly Infestation in Dogs
Botfly infestation, technically known as Cuterebra infestation, is a condition where the larvae of the Cuterebra genus (commonly called warbles or wolf worms) invade a dog's body. While these parasites primarily target rodents and rabbits, dogs can become unintended hosts—especially if they spend time outdoors near rodent or rabbit burrows and nests.
How Does Botfly Infestation Occur?
The lifecycle of the botfly begins when adult females lay eggs in the environment. Each female can deposit over 2,000 eggs during her lifetime, placing them around animal nest entrances, runways, or on vegetation. When a dog passes through these contaminated areas—most often in late summer and early fall—the warmth from its body triggers the eggs to hatch.
- The first-stage larvae are tiny and transparent.
- They enter the dog through the mouth, nose, or open wounds (often while grooming).
- Once inside, larvae migrate to subcutaneous tissue and settle there.
This process results in a lump under the skin with a small central hole (the breathing pore), which allows the larva to access air while it develops.
Where Do Warbles Appear?
The most common locations for these lumps are the head, neck, and trunk. However, they can appear anywhere on your dog’s body. The first signs are usually:
- Matted fur from licking or scratching
- A soft swelling with a distinct central hole
This swelling (called a furuncular lesion) may discharge pus or other material and is sometimes mistaken for an abscess or cyst. If bacteria contaminate the lesion, secondary infections may develop.
Clinical Signs: What Should You Watch For?
The symptoms depend on where the larva migrates and settles:
- Skin (cutaneous form): Lump with central hole, redness, irritation or pain, matted hair, pus/discharge.
- Respiratory tract: Sneezing, nasal discharge, coughing, facial/nasal swelling, difficulty breathing.
- Ocular (eye): Conjunctivitis, eyelid swelling/discharge, inner eye inflammation.
- Nervous system: Circling behavior, ataxia (wobbliness), head tilt, seizures, fever/hypothermia/hyperthermia, paralysis or blindness.
Most infestations are limited to the skin. Rarely—and more seriously—the larva migrates internally to affect nasal passages, mouth/throat (trachea), eyes, brain or spinal cord. Small breeds like Yorkshire Terriers may be at increased risk for severe internal involvement.
Diagnosis: How Is It Confirmed?
Your veterinarian will typically diagnose botfly infestation by visually identifying and extracting the larva from a swelling with its characteristic breathing pore. If neurological symptoms suggest deeper migration (like brain involvement), imaging such as ultrasound or MRI may be used.
Treatment: What Happens Next?
- A veterinarian carefully widens the breathing hole and removes the larva intact with forceps—never squeeze it out yourself!
- The wound is cleaned thoroughly with sterile saline to remove debris and promote healing.
If improperly removed (or squeezed), parts of the larva may rupture inside your dog’s tissue—causing severe reactions like infection or even anaphylaxis. In cases involving internal organs or nervous system symptoms:
- Medications such as ivermectin may be prescribed (sometimes alongside antihistamines/steroids).
If secondary bacterial infection is present or likely after removal of the larva, antibiotics will be given.
Prognosis: What’s The Outlook?
The outlook for dogs with skin-limited infestations is generally good—wounds heal well after proper removal of the larva. However:
- If vital structures like brain/spinal cord are affected prognosis is guarded; chronic neurological problems—or even euthanasia—may result in severe cases.
Deep lesions may take weeks to months to fully heal.
Prevention Tips for Dog Owners
- Avoid letting your dog roam near rodent/rabbit burrows during high-risk periods (late summer/early fall).
- Check your dog's coat after outdoor activities for unusual lumps—especially on head/neck/trunk areas.
- Routine deworming can help reduce risk of internal complications if exposure occurs.
Main Takeaways
- A lump with a central breathing hole on your dog's skin is highly suggestive of botfly infestation.
- You should never try to remove a warble yourself; seek veterinary assistance immediately if you notice suspicious lumps—or sudden behavioral changes/breathing difficulties—in your dog.
This parasitic condition most often affects dogs living in rural/wooded environments but can occur almost anywhere except Alaska. Staying alert during peak seasons and regularly checking your pet are key steps in protecting against botflies.
